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Sample records for system gps receivers

  1. Global Positioning System Time Transfer Receiver (GPS/TTR) prototype design and initial test evaluation

    NASA Technical Reports Server (NTRS)

    Oaks, J.; Frank, A.; Falvey, S.; Lister, M.; Buisson, J.; Wardrip, C.; Warren, H.

    1982-01-01

    Time transfer equipment and techniques used with the Navigation Technology Satellites were modified and extended for use with the Global Positioning System (GPS) satellites. A prototype receiver was built and field tested. The receiver uses the GPS L1 link at 1575 MHz with C/A code only to resolve a measured range to the satellite. A theoretical range is computed from the satellite ephemeris transmitted in the data message and the user's coordinates. Results of user offset from GPS time are obtained by differencing the measured and theoretical ranges and applying calibration corrections. Results of the first field test evaluation of the receiver are presented.

  2. Scintillation-Hardened GPS Receiver

    NASA Technical Reports Server (NTRS)

    Stephens, Donald R.

    2015-01-01

    CommLargo, Inc., has developed a scintillation-hardened Global Positioning System (GPS) receiver that improves reliability for low-orbit missions and complies with NASA's Space Telecommunications Radio System (STRS) architecture standards. A software-defined radio (SDR) implementation allows a single hardware element to function as either a conventional radio or as a GPS receiver, providing backup and redundancy for platforms such as the International Space Station (ISS) and high-value remote sensing platforms. The innovation's flexible SDR implementation reduces cost, weight, and power requirements. Scintillation hardening improves mission reliability and variability. In Phase I, CommLargo refactored an open-source GPS software package with Kalman filter-based tracking loops to improve performance during scintillation and also demonstrated improved navigation during a geomagnetic storm. In Phase II, the company generated a new field-programmable gate array (FPGA)-based GPS waveform to demonstrate on NASA's Space Communication and Navigation (SCaN) test bed.

  3. Next generation digital GPS receiver

    NASA Astrophysics Data System (ADS)

    Frank, G. B.; Yakos, Michael D.

    1990-07-01

    The architecture and technology features of the next-generation (NGR) digital GPS receiver manufactured by Collins are described. The project's objective was to develop an advanced GPS receiver chipset with high antijam capabilities. The program, initiated in 1985, has provided the technology for miniature receiver products for both unmanned and manned vehicle applications. A two-channel version of the receiver is currently in full-scale development for tactical missile applications. A five-channel version is being tested and evaluated as a drop-in replacement for RCVR-3A, the US Department of Defense standard high dynamic receiver. The NGR design started with the digital signal processing architecture developed for the Defense Advanced Research Project Agency (DARPA) hand-held GPS receiver. Enhancements were made to improve the antijam and signal acquisition performance. Producible, qualifiable and cost-effective silicon monolithic microwave integrated circuits and semicustom digital technologies were used to develop the core GPS chipset. A system design approach was established to permit reuse of mature and validated GPS software.

  4. GPS navigation experiment using high precision GPS timing receivers

    NASA Technical Reports Server (NTRS)

    Buisson, J. A.; Oaks, O. J.; Lister, M. J.; Wardrip, S. C.; Leschiutta, S.; Galliano, P. G.; Cordara, D.; Pettiti, V.; Detoma, E.; Dachel, P.

    1985-01-01

    Global Positioning System (GPS) Time Transfer receivers were developed by the Naval Research Laboratory (NRL) to provide synchronization for the NASA Global Laser Tracking Network (GLTN). The capabilities of the receiver are being expanded mainly through software modification to: Demonstrate the position location capabilities of a single channel receiver unsign the GPS C/A code; and Demonstrate the time/navigation capability of the receiver onboard a moving platform, by sequential tracking of GPS satellites.

  5. Portable device to assess dynamic accuracy of global positioning systems (GPS) receivers used in agricultural aircraft

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A device was designed to test the dynamic accuracy of Global Positioning System (GPS) receivers used in aerial vehicles. The system works by directing a sun-reflected light beam from the ground to the aircraft using mirrors. A photodetector is placed pointing downward from the aircraft and circuitry...

  6. Design study of a low cost civil aviation GPS receiver system

    NASA Technical Reports Server (NTRS)

    Cnossen, R.; Gilbert, G. A.

    1979-01-01

    A low cost Navstar receiver system for civil aviation applications was defined. User objectives and constraints were established. Alternative navigation processing design trades were evaluated. Receiver hardware was synthesized by comparing technology projections with various candidate system designs. A control display unit design was recommended as the result of field test experience with Phase I GPS sets and a review of special human factors for general aviation users. Areas requiring technology development to ensure a low cost Navstar Set in the 1985 timeframe were identified.

  7. Assessment of a non-dedicated GPS receiver system for precise airborne attitude determination

    SciTech Connect

    Cannon, M.E.; Sun, H.; Owen, T.E.; Meindl, M.A.

    1994-09-01

    The use of a non-dedicated GPS receiver system for attitude determination was assessed in airborne mode through a test conducted at Sandia National Laboratories. Four independent NovAtel GPSCard{trademark} receivers were installed in Sandia`s Twin Engine Otter with two antennas mounted on the fuselage and two on the wing tips at separations of 6 to 18 m. A strapdown INS was also on board the aircraft in order to provide an independent attitude reference at rates between 4 and 10 Hz. During the multi-day test, GPS measurements were recorded between 1 and 10 Hz. Carrier phase measurements were post-processed using a double difference approach developed at The University of Calgary in which integer ambiguities were resolved in seconds using the known antenna separations as constraints. The tracking capability of the system is demonstrated under dynamics consisting of roll and pitch angles up to 45 and 12 degrees, respectively. Comparisons between the GPS and INS attitude angles are presented for two of the test days and show agreement at the several arcminute level. Conclusions are made with respect to system accuracy and performance in an operational airborne environment.

  8. PiVoT GPS Receiver

    NASA Technical Reports Server (NTRS)

    Wennersten, Miriam; Banes, Vince; Boegner, Greg; Clagnett, Charles; Dougherty, Lamar; Edwards, Bernard; Roman, Joe; Bauer, Frank H. (Technical Monitor)

    2001-01-01

    NASA Goddard Space Flight Center has built an open architecture, 24 channel spaceflight Global Positioning System (GPS) receiver. The compact PCI PiVoT GPS receiver card is based on the Mitel/GEC Plessey Builder 2 board. PiVoT uses two Plessey 2021 correlators to allow tracking of up to 24 separate GPS SV's on unique channels. Its four front ends can support four independent antennas, making it a useful card for hosting GPS attitude determination algorithms. It has been built using space quality, radiation tolerant parts. The PiVoT card works at a lower signal to noise ratio than the original Builder 2 board. It also hosts an improved clock oscillator. The PiVoT software is based on the original Piessey Builder 2 software ported to the Linux operating system. The software is posix compliant and can be easily converted to other posix operating systems. The software is open source to anyone with a licensing agreement with Plessey. Additional tasks can be added to the software to support GPS science experiments or attitude determination algorithms. The next generation PiVoT receiver will be a single radiation hardened compact PCI card containing the microprocessor and the GPS receiver optimized for use above the GPS constellation.

  9. Tsunami Early Warning: Introducing single frequency GPS receiver into the Tsunami Early Warning System

    NASA Astrophysics Data System (ADS)

    Ramatschi, M.; Falck, C.

    2009-12-01

    M. Ramatschi (1), C. Falck (1), M. Bartsch (1), A. Merx (1), J. Hoeberechts (1), G. Schmidt (1) Abstract After the disastrous tsunami event in Sumatra in 2004 the German government initiated the German Indonesian Tsunami Early Warning System (GITEWS) which was inaugurated in 2008 and is now known as the Tsunami Early Warning System in Indonesia (INA-TEWS). Within GITEWS, some new technologies were introduced into the Tsunami early warning, such as geodetic dual frequency GNSS receiver, which are installed on open sea buoys, coastal tide gauges and inland reference stations. This technology is able to support tsunami early warning systems, e.g., by detection of ground motions due to earthquakes. The major drawback of this sensor type is its high expense. Under certain circumstances cost effective single frequency receiver could achieve the same quality, as long as the network topology allows a precise data processing. In our presentation we will review the GNSS part of GITEWS to demonstrate the integration of the newly designed, low power single frequency GPS sensor station with respect to the real-time data flow and the precise near real-time data processing. Technical aspects of data transmission will be addressed as well. Benefits of a small GPS sensor array located next to the Sumatra trench will be discussed in detail. (1) GeoForschungsZentrum Potsdam, Telegrafenberg A 17, D-14473 Potsdam, Germany

  10. PiVoT GPS Receiver

    NASA Technical Reports Server (NTRS)

    Wennersten, Miriam Dvorak; Banes, Anthony Vince; Boegner, Gregory J.; Dougherty, Lamar; Edwards, Bernard L.; Roman, Joseph; Bauer, Frank H. (Technical Monitor)

    2001-01-01

    NASA Goddard Space Flight Center has built an open architecture, 24 channel space flight GPS receiver. The CompactPCI PiVoT GPS receiver card is based on the Mitel/GEC Plessey Builder-2 board. PiVoT uses two Plessey 2021 correlators to allow tracking of up to 24 separate GPS SV's on unique channels. Its four front ends can support four independent antennas, making it a useful card for hosting GPS attitude determination algorithms. It has been built using space quality, radiation tolerant parts. The PiVoT card will track a weaker signal than the original Builder 2 board. It also hosts an improved clock oscillator. The PiVoT software is based on the original Plessey Builder 2 software ported to the Linux operating system. The software is POSIX complaint and can easily be converted to other POSIX operating systems. The software is open source to anyone with a licensing agreement with Plessey. Additional tasks can be added to the software to support GPS science experiments or attitude determination algorithms. The next generation PiVoT receiver will be a single radiation hardened CompactPCI card containing the microprocessor and the GPS receiver optimized for use above the GPS constellation. PiVoT was flown successfully on a balloon in July, 2001, for its first non-simulated flight.

  11. A GPS Receiver for Lunar Missions

    NASA Technical Reports Server (NTRS)

    Bamford, William A.; Heckler, Gregory W.; Holt, Greg N.; Moreau, Michael C.

    2008-01-01

    Beginning with the launch of the Lunar Reconnaissance Orbiter (LRO) in October of 2008, NASA will once again begin its quest to land humans on the Moon. This effort will require the development of new spacecraft which will safely transport people from the Earth to the Moon and back again, as well as robotic probes tagged with science, re-supply, and communication duties. In addition to the next-generation spacecraft currently under construction, including the Orion capsule, NASA is also investigating and developing cutting edge navigation sensors which will allow for autonomous state estimation in low Earth orbit (LEO) and cislunar space. Such instruments could provide an extra layer of redundancy in avionics systems and reduce the reliance on support and on the Deep Space Network (DSN). One such sensor is the weak-signal Global Positioning System (GPS) receiver "Navigator" being developed at NASA's Goddard Space Flight Center (GSFC). At the heart of the Navigator is a Field Programmable Gate Array (FPGA) based acquisition engine. This engine allows for the rapid acquisition/reacquisition of strong GPS signals, enabling the receiver to quickly recover from outages due to blocked satellites or atmospheric entry. Additionally, the acquisition algorithm provides significantly lower sensitivities than a conventional space-based GPS receiver, permitting it to acquire satellites well above the GPS constellation. This paper assesses the performance of the Navigator receiver based upon three of the major flight regimes of a manned lunar mission: Earth ascent, cislunar navigation, and entry. Representative trajectories for each of these segments were provided by NASA. The Navigator receiver was connected to a Spirent GPS signal generator, to allow for the collection of real-time, hardware-in-the-loop results for each phase of the flight. For each of the flight segments, the Navigator was tested on its ability to acquire and track GPS satellites under the dynamical

  12. Using Unmanned Aerial Vehicles and GPS Receivers

    NASA Technical Reports Server (NTRS)

    Gary, B.

    1995-01-01

    It is proposed that a small fleet of unmanned aerial vehicles (UAVs) be used over a period of years to monitor the rise of pressure surfaces caused by the hypothesized rise in average temperature of the troposphere due to global warming. Global Positioning Satellite System (GPS) receivers would be used for the precise tracking required.

  13. Shuttle Global Positioning System (GPS) design study

    NASA Technical Reports Server (NTRS)

    Nilsen, P. W.

    1979-01-01

    The effects of oscillator noise on Shuttle Global Positioning System (GPS) receiver performance, GPS navigation system self-test, GPS ground transmitter design to augment shuttle navigation, the effect of ionospheric delay modelling on GPS receiver design, and GPS receiver tracking of Shuttle transient maneuvers were investigated.

  14. High dynamic GPS receiver validation demonstration

    NASA Technical Reports Server (NTRS)

    Hurd, W. J.; Statman, J. I.; Vilnrotter, V. A.

    1985-01-01

    The Validation Demonstration establishes that the high dynamic Global Positioning System (GPS) receiver concept developed at JPL meets the dynamic tracking requirements for range instrumentation of missiles and drones. It was demonstrated that the receiver can track the pseudorange and pseudorange rate of vehicles with acceleration in excess of 100 g and jerk in excess of 100 g/s, dynamics ten times more severe than specified for conventional High Dynamic GPS receivers. These results and analytic extensions to a complete system configuration establish that all range instrumentation requirements can be met. The receiver can be implemented in the 100 cu in volume required by all missiles and drones, and is ideally suited for transdigitizer or translator applications.

  15. Development of a Miniature Multifunctional GPS Receiver for Space Applications

    NASA Astrophysics Data System (ADS)

    Miyano, Tomoyuki; Ishijima, Yoshiyuki; Kumagai, Susumu

    This paper presents the development of a miniature multifunctional GPS receiver at NASDA. The design and implementation method for a spaceborne GPS receiver has been investigated, and a breadboard model of a parallel signal search system incorporating matched filtering, an essential technique for next-generation GPS receivers, has been manufactured. The time to acquisition (TTA) of a GPS signal was measured on the breadboard model using a GPS simulator. The test results of the trial product show that TTA is within 60 msec, and time to first fix (TTFF) of the navigation calculation in a low-altitude orbit is within 5.3 min in the worst-case scenario.

  16. Processing In A GPS Receiver To Reduce Multipath Errors

    NASA Technical Reports Server (NTRS)

    Meehan, Thomas K.

    1994-01-01

    Four techniques of ancillary real-time digital processing of signals in Global Positioning System, GPS, receiver introduced reducing effects of multipath propagation of signals on position estimates produced by receiver. Multipath range errors halved. Applied in addition to other signal-processing techniques and to other techniques designing as receiving antenna to make it insensitive to reflections of GPS signals from nearby objects.

  17. Front end for GPS receivers

    NASA Technical Reports Server (NTRS)

    Thomas, Jr., Jess Brooks (Inventor)

    1999-01-01

    The front end in GPS receivers has the functions of amplifying, down-converting, filtering and sampling the received signals. In the preferred embodiment, only two operations, A/D conversion and a sum, bring the signal from RF to filtered quadrature baseband samples. After amplification and filtering at RF, the L1 and L2 signals are each sampled at RF at a high selected subharmonic rate. The subharmonic sample rates are approximately 900 MHz for L1 and 982 MHz for L2. With the selected subharmonic sampling, the A/D conversion effectively down-converts the signal from RF to quadrature components at baseband. The resulting sample streams for L1 and L2 are each reduced to a lower rate with a digital filter, which becomes a straight sum in the simplest embodiment. The frequency subsystem can be very simple, only requiring the generation of a single reference frequency (e.g. 20.46 MHz minus a small offset) and the simple multiplication of this reference up to the subharmonic sample rates for L1 and L2. The small offset in the reference frequency serves the dual purpose of providing an advantageous offset in the down-converted carrier frequency and in the final baseband sample rate.

  18. Pre-Flight Testing of Spaceborne GPS Receivers Using a GPS Constellation Simulator

    NASA Technical Reports Server (NTRS)

    Kizhner, Semion; Davis, Edward; Alonso, Roberto

    1999-01-01

    The NASA Goddard Space Flight Center (GSFC) Global Positioning System (GPS) applications test facility has been established within the GSFC Guidance Navigation and Control Center. The GPS test facility is currently housing the Global Simulation Systems Inc. (GSSI) STR2760 GPS satellite 40-channel attitude simulator and a STR4760 12-channel navigation simulator. The facility also contains a few other resources such as an atomic time standard test bed, a rooftop antenna platform and a radome. It provides a new capability for high dynamics GPS simulations of space flight that is unique within the aerospace community. The GPS facility provides a critical element for the development and testing of GPS based technologies i.e. position, attitude and precise time determination used on-board a spacecraft, suborbital rocket or balloon. The GPS simulator system is configured in a transportable rack and is available for GPS component development as well as for component, spacecraft subsystem and system level testing at spacecraft integration and test sites. The GPS facility has been operational since early 1996 and has been utilized by space flight projects carrying GPS experiments, such as the OrbView-2 and the Argentine SAC-A spacecrafts. The SAC-A pre-flight test data obtained by using the STR2760 simulator and the comparison with preliminary analysis of the GPS data from SAC-A telemetry are summarized. This paper describes pre-flight tests and simulations used to support a unique spaceborne GPS experiment. The GPS experiment mission objectives and the test program are described, as well as the GPS test facility configuration needed to verify experiment feasibility. Some operational and critical issues inherent in GPS receiver pre-flight tests and simulations using this GPS simulator, and test methodology are described. Simulation and flight data are presented. A complete program of pre-flight testing of spaceborne GPS receivers using a GPS constellation simulator is

  19. Pre-Flight Testing of Spaceborne GPS Receivers using a GPS Constellation Simulator

    NASA Technical Reports Server (NTRS)

    Kizhner, Semion; Davis, Edward; Alonso, R.

    1999-01-01

    The NASA Goddard Space Flight Center (GSFC) Global Positioning System (GPS) applications test facility has been established within the GSFC Guidance Navigation and Control Center. The GPS test facility is currently housing the Global Simulation Systems Inc. (GSSI) STR2760 GPS satellite 40-channel attitude simulator and a STR4760 12-channel navigation simulator. The facility also contains a few other resources such as an atomic time standard test bed, a rooftop antenna platform and a radome. It provides a new capability for high dynamics GPS simulations of space flight that is unique within the aerospace community. The GPS facility provides a critical element for the development and testing of GPS based technologies i.e. position, attitude and precise time determination used on-board a spacecraft, suborbital rocket balloon. The GPS simulation system is configured in a transportable rack and is available for GPS component development as well as for component, spacecraft subsystem and system level testing at spacecraft integration and tests sites. The GPS facility has been operational since early 1996 and has utilized by space flight projects carrying GPS experiments, such as the OrbView-2 and the Argentine SAC-A spacecrafts. The SAC-A pre-flight test data obtained by using the STR2760 simulator and the comparison with preliminary analysis of the GPS data from SAC-A telemetry are summarized. This paper describes pre-flight tests and simulations used to support a unique spaceborne GPS experiment. The GPS experiment mission objectives and the test program are described, as well as the GPS test facility configuration needed to verify experiment feasibility. Some operational and critical issues inherent in GPS receiver pre-flight tests and simulations using this GPS simulation, and test methodology are described. Simulation and flight data are presented. A complete program of pre-flight testing of spaceborne GPS receivers using a GPS constellation simulator is detailed.

  20. Status and potential of GPS-receiver development

    NASA Astrophysics Data System (ADS)

    Rahlfs, Dietrich

    The current development status of receivers for Navstar GPS is surveyed, with a focus on equipment for civil aircraft navigation. The basic characteristics of five-channel P-code and six-channel C/A-code receivers are reviewed and illustrated with block diagrams; recent advances in GPS antennas and signal-processing techniques are outlined; and possible approaches to a low-cost accurate aircraft system are considered. Particular attention is given to (1) a high-availability modular GPS/MLS/DME-P navigation system and (2) an integrated system combining GPS, Glonass, MLS-DME-P, and inertial navigation (e.g., a strapdown fiber-optic gyro).

  1. Evaluation of the impact of ionospheric disturbances on air navigation augmentation system using multi-point GPS receivers

    NASA Astrophysics Data System (ADS)

    Omatsu, N.; Otsuka, Y.; Shiokawa, K.; Saito, S.

    2013-12-01

    In recent years, GPS has been utilized for navigation system for airplanes. Propagation delays in the ionosphere due to total electron content (TEC) between GPS satellite and receiver cause large positioning errors. In precision measurement using GPS, the ionospheric delay correction is generally conducted using both GPS L1 and L2 frequencies. However, L2 frequency is not internationally accepted as air navigation band, so it is not available for positioning directly in air navigation. In air navigation, not only positioning accuracy but safety is important, so augmentation systems are required to ensure the safety. Augmentation systems such as the satellite-based augmentation system (SBAS) or the ground-based augmentation system (GBAS) are being developed and some of them are already in operation. GBAS is available in a relatively narrow area around airports. In general, it corrects for the combined effects of multiple sources of positioning errors simultaneously, including satellite clock and orbital information errors, ionospheric delay errors, and tropospheric delay errors, using the differential corrections broadcast by GBAS ground station. However, if the spatial ionospheric delay gradient exists in the area, correction errors remain even after correction by GBAS. It must be a threat to GBAS. In this study, we use the GPS data provided by the Geographical Survey Institute in Japan. From the GPS data, TEC is obtained every 30 seconds. We select 4 observation points from 24.4 to 35.6 degrees north latitude in Japan, and analyze TEC data of these points from 2001 to 2011. Then we reveal dependences of Rate of TEC change Index (ROTI) on latitude, season, and solar activity statistically. ROTI is the root-mean-square deviation of time subtraction of TEC within 5 minutes. In the result, it is the midnight of the spring and the summer of the solar maximum in the point of 26.4 degrees north latitude that the value of ROTI becomes the largest. We think it is caused by

  2. Single-Receiver GPS Phase Bias Resolution

    NASA Technical Reports Server (NTRS)

    Bertiger, William I.; Haines, Bruce J.; Weiss, Jan P.; Harvey, Nathaniel E.

    2010-01-01

    Existing software has been modified to yield the benefits of integer fixed double-differenced GPS-phased ambiguities when processing data from a single GPS receiver with no access to any other GPS receiver data. When the double-differenced combination of phase biases can be fixed reliably, a significant improvement in solution accuracy is obtained. This innovation uses a large global set of GPS receivers (40 to 80 receivers) to solve for the GPS satellite orbits and clocks (along with any other parameters). In this process, integer ambiguities are fixed and information on the ambiguity constraints is saved. For each GPS transmitter/receiver pair, the process saves the arc start and stop times, the wide-lane average value for the arc, the standard deviation of the wide lane, and the dual-frequency phase bias after bias fixing for the arc. The second step of the process uses the orbit and clock information, the bias information from the global solution, and only data from the single receiver to resolve double-differenced phase combinations. It is called "resolved" instead of "fixed" because constraints are introduced into the problem with a finite data weight to better account for possible errors. A receiver in orbit has much shorter continuous passes of data than a receiver fixed to the Earth. The method has parameters to account for this. In particular, differences in drifting wide-lane values must be handled differently. The first step of the process is automated, using two JPL software sets, Longarc and Gipsy-Oasis. The resulting orbit/clock and bias information files are posted on anonymous ftp for use by any licensed Gipsy-Oasis user. The second step is implemented in the Gipsy-Oasis executable, gd2p.pl, which automates the entire process, including fetching the information from anonymous ftp

  3. GPS high dynamic receiver tracking demonstration results

    NASA Technical Reports Server (NTRS)

    Hurd, W. J.; Statman, J. I.; Vilnrotter, V. A.

    1985-01-01

    Demonstration results are presented for a high dynamic GPS receiver. The receiver tested is a breadboard unit capable of tracking one simulated satellite signal in pseudorange and range rate. The receiver makes approximate maximum likelihood estimates of pseudorange and range rate each 20 ms, and tracks these observables using a third order filter with a time constant of 0.14 s. Carrier phase is not tracked, which eliminates the typical failure mode of loss of carrier lock associated with PLLs at high dynamics. The receiver tracks with pseudorange lag errors of under 0.06 m when subjected to simulated 50 g turns with 40 g/s peak jerk. Pseudorange errors due to receiver noise alone are approximately 0.6 m rms at a carrier power to noise spectral density ratio of 34 dB-Hz. The tracking threshold SNR is approximately 28 dB-Hz, which provides 12 dB margin relative to the 40 dB-Hz that occurs with minimum specified satellite signal strength, 3.5 dB system noise figure, and 0 dBi antenna gain.

  4. Real-Time Point Positioning Performance Evaluation of Single-Frequency Receivers Using NASA's Global Differential GPS System

    NASA Technical Reports Server (NTRS)

    Muellerschoen, Ronald J.; Iijima, Byron; Meyer, Robert; Bar-Sever, Yoaz; Accad, Elie

    2004-01-01

    This paper evaluates the performance of a single-frequency receiver using the 1-Hz differential corrections as provided by NASA's global differential GPS system. While the dual-frequency user has the ability to eliminate the ionosphere error by taking a linear combination of observables, the single-frequency user must remove or calibrate this error by other means. To remove the ionosphere error we take advantage of the fact that the magnitude of the group delay in range observable and the carrier phase advance have the same magnitude but are opposite in sign. A way to calibrate this error is to use a real-time database of grid points computed by JPL's RTI (Real-Time Ionosphere) software. In both cases we evaluate the positional accuracy of a kinematic carrier phase based point positioning method on a global extent.

  5. An evaluation of a UAV guidance system with consumer grade GPS receivers

    NASA Astrophysics Data System (ADS)

    Rosenberg, Abigail Stella

    Remote sensing has been demonstrated an important tool in agricultural and natural resource management and research applications, however there are limitations that exist with traditional platforms (i.e., hand held sensors, linear moves, vehicle mounted, airplanes, remotely piloted vehicles (RPVs), unmanned aerial vehicles (UAVs) and satellites). Rapid technological advances in electronics, computers, software applications, and the aerospace industry have dramatically reduced the cost and increased the availability of remote sensing technologies. Remote sensing imagery vary in spectral, spatial, and temporal resolutions and are available from numerous providers. Appendix A presented results of a test project that acquired high-resolution aerial photography with a RPV to map the boundary of a 0.42 km2 fire area. The project mapped the boundaries of the fire area from a mosaic of the aerial images collected and compared this with ground-based measurements. The project achieved a 92.4% correlation between the aerial assessment and the ground truth data. Appendix B used multi-objective analysis to quantitatively assess the tradeoffs between different sensor platform attributes to identify the best overall technology. Experts were surveyed to identify the best overall technology at three different pixel sizes. Appendix C evaluated the positional accuracy of a relatively low cost UAV designed for high resolution remote sensing of small areas in order to determine the positional accuracy of sensor readings. The study evaluated the accuracy and uncertainty of a UAV flight route with respect to the programmed waypoints and of the UAV's GPS position, respectively. In addition, the potential displacement of sensor data was evaluated based on (1) GPS measurements on board the aircraft and (2) the autopilot's circuit board with 3-axis gyros and accelerometers (i.e., roll, pitch, and yaw). The accuracies were estimated based on a 95% confidence interval or similar methods. The

  6. Networked differential GPS system

    NASA Technical Reports Server (NTRS)

    Mueller, K. Tysen (Inventor); Loomis, Peter V. W. (Inventor); Kalafus, Rudolph M. (Inventor); Sheynblat, Leonid (Inventor)

    1994-01-01

    An embodiment of the present invention relates to a worldwide network of differential GPS reference stations (NDGPS) that continually track the entire GPS satellite constellation and provide interpolations of reference station corrections tailored for particular user locations between the reference stations Each reference station takes real-time ionospheric measurements with codeless cross-correlating dual-frequency carrier GPS receivers and computes real-time orbit ephemerides independently. An absolute pseudorange correction (PRC) is defined for each satellite as a function of a particular user's location. A map of the function is constructed, with iso-PRC contours. The network measures the PRCs at a few points, so-called reference stations and constructs an iso-PRC map for each satellite. Corrections are interpolated for each user's site on a subscription basis. The data bandwidths are kept to a minimum by transmitting information that cannot be obtained directly by the user and by updating information by classes and according to how quickly each class of data goes stale given the realities of the GPS system. Sub-decimeter-level kinematic accuracy over a given area is accomplished by establishing a mini-fiducial network.

  7. High dynamic, low volume GPS receiver

    NASA Technical Reports Server (NTRS)

    Hurd, W. J.

    1983-01-01

    A new GPS receiver concept and design are presented to meet the high dynamic and low volume requirements for range applications in missiles and drones. The receiver has the potential to satisfy all range requirements with one basic receiver, which has significant potential economic benefit over the alternate approach of using a family of receivers, each tailored for specific applications. The main new concept is to use approximate maximum likelihood estimates of pseudo range and range-rate, rather than tracking with carrier phase locked loops and code delay locked loops. Preliminary analysis indicates that receivers accelerating at 50 g or more can track with position errors due to acceleration of approximately 0.2 m/g, or 10 m at 50 g. Implementation is almost entirely digital to meet the low volume requirements.

  8. How Bad Receiver Coordinates Can Affect GPS Timing

    NASA Technical Reports Server (NTRS)

    Chadsey, H.

    1996-01-01

    Many sources of error are possible when the Global Positioning System (GPS) is used for time comparisons. Some of these errors have been listed by Lewandowski. Because of the complexity of the system, an error source could have more than one effect. This paper will present theoretical and observational results by offsetting a receiver's coordinates. The calculations show how an error as small as three meters in any direction can result in a timing error of more than 10 nanoseconds. The GPS receiver must be surveyed to better than 0.2 meter accuracy for the timing error to be sub-nanosecond.

  9. Impact of Swarm GPS receiver updates on POD performance

    NASA Astrophysics Data System (ADS)

    van den IJssel, Jose; Forte, Biagio; Montenbruck, Oliver

    2016-05-01

    The Swarm satellites are equipped with state-of-the-art Global Positioning System (GPS) receivers, which are used for the precise geolocation of the magnetic and electric field instruments, as well as for the determination of the Earth's gravity field, the total electron content and low-frequency thermospheric neutral densities. The onboard GPS receivers deliver high-quality data with an almost continuous data rate. However, the receivers show a slightly degraded performance when flying over the geomagnetic poles and the geomagnetic equator, due to ionospheric scintillation. Furthermore, with only eight channels available for dual-frequency tracking, the amount of collected GPS tracking data is relatively low compared with various other missions. Therefore, several modifications have been implemented to the Swarm GPS receivers. To optimise the amount of collected GPS data, the GPS antenna elevation mask has slowly been reduced from 10° to 2°. To improve the robustness against ionospheric scintillation, the bandwidths of the GPS receiver tracking loops have been widened. Because these modifications were first implemented on Swarm-C, their impact can be assessed by a comparison with the close flying Swarm-A satellite. This shows that both modifications have a positive impact on the GPS receiver performance. The reduced elevation mask increases the amount of GPS tracking data by more than 3 %, while the updated tracking loops lead to around 1.3 % more observations and a significant reduction in tracking losses due to severe equatorial scintillation. The additional observations at low elevation angles increase the average noise of the carrier phase observations, but nonetheless slightly improve the resulting reduced-dynamic and kinematic orbit accuracy as shown by independent satellite laser ranging (SLR) validation. The more robust tracking loops significantly reduce the large carrier phase observation errors at the geomagnetic poles and along the geomagnetic

  10. Shuttle Global Positioning System (GPS) system design study

    NASA Technical Reports Server (NTRS)

    Nilsen, P. W.

    1979-01-01

    The various integration problems in the Shuttle GPS system were investigated. The analysis of the Shuttle GPS link was studied. A preamplifier was designed since the Shuttle GPS antennas must be located remotely from the receiver. Several GPS receiver architecture trade-offs were discussed. The Shuttle RF harmonics and intermode that fall within the GPS receiver bandwidth were analyzed. The GPS PN code acquisition was examined. Since the receiver clock strongly affects both GPS carrier and code acquisition performance, a clock model was developed.

  11. Going Up. A GPS Receiver Adapts to Space

    NASA Technical Reports Server (NTRS)

    Lightsey, E. Glenn; Simpson, James E.

    2000-01-01

    Current plans for the space station call for the GPS receiver to be installed on the U.S. lab module of the station in early 2001 (ISS Assembly Flight SA), followed by the attachment of the antenna array in late 2001 (Flight 8A). At that point the U.S. ISS guidance and control system will be operational. The flight of SIGI on the space station represents a "coming of age" for GPS technology on spacecraft. For at least a decade, the promise of using GPS receivers to automate spacecraft operations, simplify satellite design, and reduce mission costs has enticed satellite designers. Integration of this technology onto spacecraft has been slower than some originally anticipated. However, given the complexity of the GPS sensor, and the importance of the functions it performs, its incorporation into mainstream satellite design has probably occurred at a very reasonable pace. Going from providing experimental payloads on small, unmanned satellites to performing critical operational functions on manned vehicles has been a major evolution. If all goes as planned in the next few months, GPS receivers will soon provide those critical functions on one of the most complex spacecraft in history, the International Space Station.

  12. An auroral scintillation observation using precise, collocated GPS receivers

    NASA Astrophysics Data System (ADS)

    Garner, T. W.; Harris, R. B.; York, J. A.; Herbster, C. S.; Minter, C. F., III; Hampton, D. L.

    2011-02-01

    On 10 January 2009, an unusual ionospheric scintillation event was observed by a Global Positioning System (GPS) receiver station in Fairbanks, Alaska. The receiver station is part of the National Geospatial-Intelligence Agency's (NGA) Monitoring Station Network (MSN). Each MSN station runs two identical geodetic-grade, dual-frequency, full-code tracking GPS receivers that share a common antenna. At the Fairbanks station, a third separate receiver with a separate antenna is located nearby. During the 10 January event, ionospheric conditions caused two of the receivers to loose lock on a single satellite. The third receiver tracked through the scintillation. The region of scintillation was collocated with an auroral arc and a slant total electron content (TEC) increase of 5.71 TECu (TECu = 1016/m2). The response of the full-code tracking receivers to the scintillation is intriguing. One of these receivers lost lock, but the other receiver did not. This fact argues that a receiver's internal state dictates its reaction to scintillation. Additionally, the scintillation only affected the L2 signal. While this causes the L1 signal to be lost on the semicodelessly receiver, the full-code tracking receiver only lost the L1 signal when the receiver attempted to reacquire the satellite link.

  13. Software Defined GPS Receiver for International Space Station

    NASA Technical Reports Server (NTRS)

    Duncan, Courtney B.; Robison, David E.; Koelewyn, Cynthia Lee

    2011-01-01

    JPL is providing a software defined radio (SDR) that will fly on the International Space Station (ISS) as part of the CoNNeCT project under NASA's SCaN program. The SDR consists of several modules including a Baseband Processor Module (BPM) and a GPS Module (GPSM). The BPM executes applications (waveforms) consisting of software components for the embedded SPARC processor and logic for two Virtex II Field Programmable Gate Arrays (FPGAs) that operate on data received from the GPSM. GPS waveforms on the SDR are enabled by an L-Band antenna, low noise amplifier (LNA), and the GPSM that performs quadrature downconversion at L1, L2, and L5. The GPS waveform for the JPL SDR will acquire and track L1 C/A, L2C, and L5 GPS signals from a CoNNeCT platform on ISS, providing the best GPS-based positioning of ISS achieved to date, the first use of multiple frequency GPS on ISS, and potentially the first L5 signal tracking from space. The system will also enable various radiometric investigations on ISS such as local multipath or ISS dynamic behavior characterization. In following the software-defined model, this work will create a highly portable GPS software and firmware package that can be adapted to another platform with the necessary processor and FPGA capability. This paper also describes ISS applications for the JPL CoNNeCT SDR GPS waveform, possibilities for future global navigation satellite system (GNSS) tracking development, and the applicability of the waveform components to other space navigation applications.

  14. Coastal sea level measurements using a single geodetic GPS receiver

    NASA Astrophysics Data System (ADS)

    Larson, Kristine M.; Löfgren, Johan S.; Haas, Rüdiger

    2013-04-01

    This paper presents a method to derive local sea level variations using data from a single geodetic-quality Global Navigation Satellite System (GNSS) receiver using GPS (Global Positioning System) signals. This method is based on multipath theory for specular reflections and the use of Signal-to-Noise Ratio (SNR) data. The technique could be valuable for altimeter calibration and validation. Data from two test sites, a dedicated GPS tide gauge at the Onsala Space Observatory (OSO) in Sweden and the Friday Harbor GPS site of the EarthScope Plate Boundary Observatory (PBO) in USA, are analyzed. The sea level results are compared to independently observed sea level data from nearby and in situ tide gauges. For OSO, the Root-Mean-Square (RMS) agreement is better than 5 cm, while it is in the order of 10 cm for Friday Harbor. The correlation coefficients are better than 0.97 for both sites. For OSO, the SNR-based results are also compared with results from a geodetic analysis of GPS data of a two receivers/antennae tide gauge installation. The SNR-based analysis results in a slightly worse RMS agreement with respect to the independent tide gauge data than the geodetic analysis (4.8 cm and 4.0 cm, respectively). However, it provides results even for rough sea surface conditions when the two receivers/antennae installation no longer records the necessary data for a geodetic analysis.

  15. Fast-Acquisition/Weak-Signal-Tracking GPS Receiver for HEO

    NASA Technical Reports Server (NTRS)

    Wintemitz, Luke; Boegner, Greg; Sirotzky, Steve

    2004-01-01

    A report discusses the technical background and design of the Navigator Global Positioning System (GPS) receiver -- . a radiation-hardened receiver intended for use aboard spacecraft. Navigator is capable of weak signal acquisition and tracking as well as much faster acquisition of strong or weak signals with no a priori knowledge or external aiding. Weak-signal acquisition and tracking enables GPS use in high Earth orbits (HEO), and fast acquisition allows for the receiver to remain without power until needed in any orbit. Signal acquisition and signal tracking are, respectively, the processes of finding and demodulating a signal. Acquisition is the more computationally difficult process. Previous GPS receivers employ the method of sequentially searching the two-dimensional signal parameter space (code phase and Doppler). Navigator exploits properties of the Fourier transform in a massively parallel search for the GPS signal. This method results in far faster acquisition times [in the lab, 12 GPS satellites have been acquired with no a priori knowledge in a Low-Earth-Orbit (LEO) scenario in less than one second]. Modeling has shown that Navigator will be capable of acquiring signals down to 25 dB-Hz, appropriate for HEO missions. Navigator is built using the radiation-hardened ColdFire microprocessor and housing the most computationally intense functions in dedicated field-programmable gate arrays. The high performance of the algorithm and of the receiver as a whole are made possible by optimizing computational efficiency and carefully weighing tradeoffs among the sampling rate, data format, and data-path bit width.

  16. Estimating Total Electron Content Using 1,000+ GPS Receivers

    NASA Technical Reports Server (NTRS)

    Komjathy, Attila; Mannucci, Anthony

    2006-01-01

    A computer program uses data from more than 1,000 Global Positioning System (GPS) receivers in an Internet-accessible global network to generate daily estimates of the global distribution of vertical total electron content (VTEC) of the ionosphere. This program supersedes an older program capable of processing readings from only about 200 GPS receivers. This program downloads the data via the Internet, then processes the data in three stages. In the first stage, raw data from a global subnetwork of about 200 receivers are preprocessed, station by station, in a Kalman-filter-based least-squares estimation scheme that estimates satellite and receiver differential biases for these receivers and for satellites. In the second stage, an observation equation that incorporates the results from the first stage and the raw data from the remaining 800 receivers is solved to obtain the differential biases for these receivers. The only remaining error sources for which an account cannot be given are multipath and receiver noise contributions. The third stage is a postprocessing stage in which all the processed data are combined and used to generate new data products, including receiver differential biases and global and regional VTEC maps and animations.

  17. Architecture and performance of a new GPS time transfer and positioning receiver

    NASA Technical Reports Server (NTRS)

    Kido, T. I.; Ould, P. C.; Vanwechel, R. J.

    1983-01-01

    This paper describes the Interstate Electronics 4200 GPS Receiver System that has been developed for time transfer and low dynamic positioning applications. The receiver employs the NAVSTAR Global Positioning System (GPS) l sub 1 C/A code and has three optional solution modes fo the clock/navigation state estimation.

  18. NAVIGATION PERFORMANCE IN HIGH EARTH ORBITS USING NAVIGATOR GPS RECEIVER

    NASA Technical Reports Server (NTRS)

    Bamford, William; Naasz, Bo; Moreau, Michael C.

    2006-01-01

    NASA GSFC has developed a GPS receiver that can acquire and track GPS signals with sensitivity significantly lower than conventional GPS receivers. This opens up the possibility of using GPS based navigation for missions in high altitude orbit, such as Geostationary Operational Environmental Satellites (GOES) in a geostationary orbit, and the Magnetospheric MultiScale (MMS) Mission, in highly eccentric orbits extending to 12 Earth radii and higher. Indeed much research has been performed to study the feasibility of using GPS navigation in high Earth orbits and the performance achievable. Recently, GSFC has conducted a series of hardware in-the-loop tests to assess the performance of this new GPS receiver in various high Earth orbits of interest. Tracking GPS signals to down to approximately 22-25 dB-Hz, including signals from the GPS transmitter side-lobes, steady-state navigation performance in a geostationary orbit is on the order of 10 meters. This paper presents the results of these tests, as well as sensitivity analysis to such factors as ionosphere masks, use of GPS side-lobe signals, and GPS receiver sensitivity.

  19. Low-cost digital GPS receiver with software carrier detection

    NASA Astrophysics Data System (ADS)

    Wolf, M. H.

    1988-08-01

    The satellite navigation system global positioning system (GPS) will play a major role in the field of navigation. It will be able to compete with all previously existing radio navigation systems. Low-cost receivers will be built for a number of civilian users, such as general aviation, sea and land navigation. To permit production at low cost for the civil market, a new technique for a C/A (course and acquisition) code receiver has been developed. All the signal detecting and processing is carried out with the digital signal processing software in a Texas Instruments TMS 320C10. The advantage of this method is that complex functions can be effected in a computer program instead of in analog or digital circuits. This reduces the costs of the parts used in the receiver and also avoids calibration. Taken together, these two features greatly reduce the price of a navigation set. This paper discusses the underlying principles leading to this new receiver.

  20. Fault tolerant GPS/Inertial System design

    NASA Astrophysics Data System (ADS)

    Brown, Alison K.; Sturza, Mark A.; Deangelis, Franco; Lukaszewski, David A.

    The use of a GPS/Inertial integrated system in future launch vehicles motivates the described design of the present fault-tolerant system. The robustness of the navigation system is enhanced by integrating the GPS with an inertial fault-tolerant system. Three layers of failure detection and isolation are incorporated to determine the nature of flaws in the inertial instruments, the GPS receivers, or the integrated navigation solution. The layers are based on: (1) a high-rate parity algorithm for instrument failures; (2) a similar parity algorithm for GPS satellite or receiver failures; and (3) a GPS navigation solution to monitor inertial navigation failures. Dual failures of any system component can occur in any system component without affecting the performance of launch-vehicle navigation or guidance.

  1. GPS Antenna Characterization Experiment (ACE): Receiver Design and Initial Results

    NASA Technical Reports Server (NTRS)

    Martzen, Phillip; Highsmith, Dolan E.; Valdez, Jennifer E.; Parker, Joel J. K.; Moreau, Michael C.

    2015-01-01

    The GPS Antenna Characterization Experiment (ACE) is a research collaboration between Aerospace and NASA Goddard to characterize the gain patterns of the GPS L1 transmit antennas. High altitude GPS observations are collected at a ground station through a transponder-based or "bent-pipe" architecture where the GPS L1 RF spectrum is received at a platform in geosynchronous orbit and relayed to the ground for processing. The focus of this paper is the unique receiver algorithm design and implementation. The high-sensitivity GPS C/A-code receiver uses high fidelity code and carrier estimates and externally supplied GPS message bit data in a batch algorithm with settings for a 0 dB-Hz threshold. The resulting carrier-to-noise measurements are used in a GPS L1 transmit antenna pattern reconstruction. This paper shows initial transmit gain patterns averaged over each block of GPS satellites, including comparisons to available pre-flight gain measurements from the GPS vehicle contractors. These results provide never-before-seen assessments of the full, in-flight transmit gain patterns.

  2. Building a GPS Receiver for Space Lessons Learned

    NASA Technical Reports Server (NTRS)

    Sirotzky, Steve; Heckler, G. W.; Boegner, G.; Roman, J.; Wennersten, M.; Butler, R.; Davis, M.; Lanham, A.; Winternitz, L.; Thompson, W.; Bamford, B.; Banes, V.

    2008-01-01

    Over the past 4 years the Component Systems and Hardware branch at NASA GSFC has pursued an inhouse effort to build a unique space-flight GPS receiver. This effort has resulted in the Navigator GPS receiver. Navigator's first flight opportunity will come with the STS-125 HST-SM4 mission in August 2008. This paper covers the overall hardware design for the receiver and the difficulties encountered during the transition from the breadboard design to the final flight hardware design. Among the different lessons learned, the paper stresses the importance of selecting and verifying parts that are appropriate for space applications, as well as what happens when these parts are not accurately characterized by their datasheets. Additionally, the paper discusses what analysis needs to be performed when deciding system frequencies and filters. The presentation also covers how to prepare for thermal vacuum testing, and problems that may arise during vibration testing. It also contains what criteria should be considered when determining which portions of a design to create in-house, and which portions to license from a third party. Finally, the paper shows techniques which have proven to be extraordinarily helpful in debugging and analysis.

  3. Pre-Flight Testing of Spaceborne GPS Receivers Using a GPS Constellation Simulator

    NASA Technical Reports Server (NTRS)

    Kizhner, Semion; Alonso, Roberto

    1999-01-01

    The NASA Goddard Space Flight Center (GSFC) Global Positioning System (GPS) test facility has been established within the GSFC Guidance Navigation and Control Center. The GPS test facility is currently housing the STR2760 GPS satellite 40-channel attitude simulator and an STR4760 12-channel navigation simulator. The facility also contains a few other Goddard resources such as an atomic time standard test bed, a rooftop antenna platform and a radome. It provides a new capability of high dynamics GPS simulations for space flight that is unique within the aerospace community. The GPS facility gives a significant advantage in the development and support of GPS based technologies for position, attitude and precise time determination on-board a spacecraft, sounding rocket or balloon. The GPS simulator system is configured in a transportable rack and is available for GPS applications' component development as well as for spacecraft subsystem and system level testing at spacecraft integration and test sites. The GPS facility has been operational since early 1996 and has been already utilized by a few successful flight projects carrying GPS experiments, such as USA Seastar satellite and the first Argentine satellite SAC-A. The experience in the SAC-A pre-flight testing using the STR2760 simulator is summarized as well as the comparison with preliminary analysis of the GPS data from SAC-A telemetry.

  4. Range filtering for sequential GPS receivers

    NASA Technical Reports Server (NTRS)

    Paielli, Russell

    1987-01-01

    The filtering of the satellite range and range-rate measurements from single channel sequential Global Positioning System receivers is usually done with an extended Kalman filter which has state variables defined in terms of an orthogonal navigation reference frame. An attractive suboptimal alternative is range-domain filtering, in which the individual satellite measurements are filtered separately before they are combined for the navigation solution. The main advantages of range-domain filtering are decreased processing and storage requirements and simplified tuning. Several range filter mechanization alternatives are presented, along with an innovative approach for combining the filtered range-domain quantities to determine the navigation state estimate. In addition, a method is outlined for incorporating measurements from auxiliary sensors such as altimeters into the navigation state estimation scheme similarly to the satellite measurements. A method is also described for incorporating inertial measurements into the navigation state estimator as a process driver.

  5. Development And Test of A Digitally Steered Antenna Array for The Navigator GPS Receiver

    NASA Technical Reports Server (NTRS)

    Pinto, Heitor David; Valdez, Jennifer E.; Winternitz, Luke M. B.; Hassouneh, Munther A.; Price, Samuel R.

    2012-01-01

    Global Positioning System (GPS)-based navigation has become common for low-Earth orbit spacecraft as the signal environment is similar to that on the Earth s surface. The situation changes abruptly, however, for spacecraft whose orbital altitudes exceed that of the GPS constellation. Visibility is dramatically reduced and signals that are present may be very weak and more susceptible to interference. GPS receivers effective at these altitudes require increased sensitivity, which often requires a high-gain antenna. Pointing such an antenna can pose a challenge. One efficient approach to mitigate these problems is the use of a digitally steered antenna array. Such an antenna can optimally allocate gain toward desired signal sources and away from interferers. This paper presents preliminary results in the development and test of a digitally steered antenna array for the Navigator GPS research program at NASA s Goddard Space Flight Center. In particular, this paper highlights the development of an array and front-end electronics, the development and test of a real-time software GPS receiver, and implementation of three beamforming methods for combining the signals from the array. Additionally, this paper discusses the development of a GPS signal simulator which produces digital samples of the GPS L1C/A signals as they would be received by an arbitrary antenna array configuration. The simulator models transmitter and receiver dynamics, near-far and multipath interference, and has been a critical component in both the development and test of the GPS receiver. The GPS receiver system was tested with real and simulated GPS signals. Preliminary results show that performance improvement was achieved in both the weak signal and interference environments, matching analytical predictions. This paper summarizes our initial findings and discusses the advantages and limitations of the antenna array and the various beamforming methods.

  6. High-precision coseismic displacement estimation with a single-frequency GPS receiver

    NASA Astrophysics Data System (ADS)

    Guo, Bofeng; Zhang, Xiaohong; Ren, Xiaodong; Li, Xingxing

    2015-07-01

    To improve the performance of Global Positioning System (GPS) in the earthquake/tsunami early warning and rapid response applications, minimizing the blind zone and increasing the stability and accuracy of both the rapid source and rupture inversion, the density of existing GPS networks must be increased in the areas at risk. For economic reasons, low-cost single-frequency receivers would be preferable to make the sparse dual-frequency GPS networks denser. When using single-frequency GPS receivers, the main problem that must be solved is the ionospheric delay, which is a critical factor when determining accurate coseismic displacements. In this study, we introduce a modified Satellite-specific Epoch-differenced Ionospheric Delay (MSEID) model to compensate for the effect of ionospheric error on single-frequency GPS receivers. In the MSEID model, the time-differenced ionospheric delays observed from a regional dual-frequency GPS network to a common satellite are fitted to a plane rather than part of a sphere, and the parameters of this plane are determined by using the coordinates of the stations. When the parameters are known, time-differenced ionospheric delays for a single-frequency GPS receiver could be derived from the observations of those dual-frequency receivers. Using these ionospheric delay corrections, coseismic displacements of a single-frequency GPS receiver can be accurately calculated based on time-differenced carrier-phase measurements in real time. The performance of the proposed approach is validated using 5 Hz GPS data collected during the 2012 Nicoya Peninsula Earthquake (Mw 7.6, 2012 September 5) in Costa Rica. This shows that the proposed approach improves the accuracy of the displacement of a single-frequency GPS station, and coseismic displacements with an accuracy of a few centimetres are achieved over a 10-min interval.

  7. Using ionospheric scintillation indices to estimate GPS receiver tracking performance

    NASA Astrophysics Data System (ADS)

    Elmas, Zeynep G.; Aquino, Marcio; Dodson, Alan

    2010-05-01

    The Institute of Engineering Surveying and Space Geodesy (IESSG), at the University of Nottingham, has been involved with ionospheric scintillation research and its impact on users of Global Navigation Satellite Systems (GNSS) since 2001. The IESSG hosts a comprehensive archive of scintillation data recorded during the last high of the solar cycle (2001-2003) by four GSV4004 receivers (GPS Silicon Valley) in the UK and Norway, at geographic latitudes varying from 53N to 71N. The scintillation data that forms this ~3-year archive is given solely by the widely used scintillation indices S4 and σφ (in particular the latter's 60 second version). Aquino et al (2007) describe a strategy devised to enable the combination of these scintillation indices and the spectral parameters T (the spectral strength of the phase noise at 1 Hz) and p (the spectral slope), extracted from high-rate GPS phase and amplitude data, with state-of-the-art receiver tracking models in order to study receiver tracking performance under scintillation conditions. Strangeways (2009) later devised a method to calculate the scintillation parameters T and p over a range of Fresnel frequencies based only on the scintillation indices, i.e. when high rate data is not available, as in the case of the IESSG archive of 2001-2003. This paper shows initial investigations on the retrieval of the spectral parameters p and T from actual GPS scintillation indices recorded more recently in Trondheim (app. Lat 64N, Long 10E) on 23 April 2008. T and p values are estimated from S4 and σφ and compared with actual spectral parameters obtained from high rate data that are now being recorded. The paper then takes investigations a step further, by comparing the output of a state of the art tracking model when the estimated and actual spectral parameters are used as input, respectively. This paper gives an initial insight on the applicability of the method to mitigate the effects of the ionospheric scintillation on

  8. Precise Clock Solutions Using Carrier Phase from GPS Receivers in the International GPS Service

    NASA Technical Reports Server (NTRS)

    Zumberge, J. F.; Jefferson, D. C.; Stowers, D. A.; Tjoelker, R. L.; Young, L. E.

    1999-01-01

    As one of its activities as an Analysis Center in the International GPS Service (IGS), the Jet Propulsion Laboratory (JPL) uses data from a globally distributed network of geodetic-quality GPS receivers to estimate precise clock solutions, relative to a chosen reference, for both the GPS satellites and GPS receiver internal clocks, every day. The GPS constellation and ground network provide geometrical strength resulting in formal errors of about 100 p sec for these estimates. Some of the receivers in the global IGS network contain high quality frequency references, such as hydrogen masers. The clock solutions for such receivers are smooth at the 20-p sec level on time scales of a few minutes. There are occasional (daily to weekly) shifts at the microsec level, symptomatic of receiver resets, and 200-p sec-level discontinuities at midnight due to 1-day processing boundaries. Relative clock solutions among 22 IGS sites proposed as "fiducial" in the IGS/BIPM pilot project have been examined over a recent 4-week period. This allows a quantitative measure of receiver reset frequency as a function of site. For days and-sites without resets, the Allan deviation of the relative clock solutions is also computed for subdaily values of tau..

  9. Predicting metabolic rate during level and uphill outdoor walking using a low-cost GPS receiver.

    PubMed

    de Müllenheim, Pierre-Yves; Dumond, Rémy; Gernigon, Marie; Mahé, Guillaume; Lavenu, Audrey; Bickert, Sandrine; Prioux, Jacques; Noury-Desvaux, Bénédicte; Le Faucheur, Alexis

    2016-08-01

    The objective of this study was to assess the accuracy of using speed and grade data obtained from a low-cost global positioning system (GPS) receiver to estimate metabolic rate (MR) during level and uphill outdoor walking. Thirty young, healthy adults performed randomized outdoor walking for 6-min periods at 2.0, 3.5, and 5.0 km/h and on three different grades: 1) level walking, 2) uphill walking on a 3.7% mean grade, and 3) uphill walking on a 10.8% mean grade. The reference MR [metabolic equivalents (METs) and oxygen uptake (V̇o2)] values were obtained using a portable metabolic system. The speed and grade were obtained using a low-cost GPS receiver (1-Hz recording). The GPS grade (Δ altitude/distance walked) was calculated using both uncorrected GPS altitude data and GPS altitude data corrected with map projection software. The accuracy of predictions using reference speed and grade (actual[SPEED/GRADE]) data was high [R(2) = 0.85, root-mean-square error (RMSE) = 0.68 MET]. The accuracy decreased when GPS speed and uncorrected grade (GPS[UNCORRECTED]) data were used, although it remained substantial (R(2) = 0.66, RMSE = 1.00 MET). The accuracy was greatly improved when the GPS speed and corrected grade (GPS[CORRECTED]) data were used (R(2) = 0.82, RMSE = 0.79 MET). Published predictive equations for walking MR were also cross-validated using actual or GPS speed and grade data when appropriate. The prediction accuracy was very close when either actual[SPEED/GRADE] values or GPS[CORRECTED] values (for level and uphill combined) or GPS speed values (for level walking only) were used. These results offer promising research and clinical applications related to the assessment of energy expenditure during free-living walking. PMID:27402559

  10. Performance Evaluation of Block Acquisition and Tracking Algorithms Using an Open Source GPS Receiver Platform

    NASA Technical Reports Server (NTRS)

    Ramachandran, Ganesh K.; Akopian, David; Heckler, Gregory W.; Winternitz, Luke B.

    2011-01-01

    Location technologies have many applications in wireless communications, military and space missions, etc. US Global Positioning System (GPS) and other existing and emerging Global Navigation Satellite Systems (GNSS) are expected to provide accurate location information to enable such applications. While GNSS systems perform very well in strong signal conditions, their operation in many urban, indoor, and space applications is not robust or even impossible due to weak signals and strong distortions. The search for less costly, faster and more sensitive receivers is still in progress. As the research community addresses more and more complicated phenomena there exists a demand on flexible multimode reference receivers, associated SDKs, and development platforms which may accelerate and facilitate the research. One of such concepts is the software GPS/GNSS receiver (GPS SDR) which permits a facilitated access to algorithmic libraries and a possibility to integrate more advanced algorithms without hardware and essential software updates. The GNU-SDR and GPS-SDR open source receiver platforms are such popular examples. This paper evaluates the performance of recently proposed block-corelator techniques for acquisition and tracking of GPS signals using open source GPS-SDR platform.

  11. Design and predicted performance of the GPS demonstration receiver for the NASA Topex satellite

    NASA Technical Reports Server (NTRS)

    Carson, Lance; Hailey, Lenard; Geier, G. Jeffrey; Davis, Robert; Huth, Gaylord; Munson, Timothy N.

    1988-01-01

    NASA's Ocean Topography Experiment (Topex) satellite will perform topographic ocean mapping. Topex will carry an experimental tracking system based on the use of GPS (Global Positioning System). An onboard GPS Demonstration Receiver (GPSDR) will be used with a network of up to ten receivers at precisely known ground sites. Following a brief overview of the Topex mission and its derived accuracy requirements, the authors describe the design of the GPSDR. The major hardware and software components are reviewed and discussed. Projected receiver tracking and navigation performance measures are presented and discussed.

  12. Comparison of GPS receiver DCB estimation methods using a GPS network

    NASA Astrophysics Data System (ADS)

    Choi, Byung-Kyu; Park, Jong-Uk; Min Roh, Kyoung; Lee, Sang-Jeong

    2013-07-01

    Two approaches for receiver differential code biases (DCB) estimation using the GPS data obtained from the Korean GPS network (KGN) in South Korea are suggested: the relative and single (absolute) methods. The relative method uses a GPS network, while the single method determines DCBs from a single station only. Their performance was assessed by comparing the receiver DCB values obtained from the relative method with those estimated by the single method. The daily averaged receiver DCBs obtained from the two different approaches showed good agreement for 7 days. The root mean square (RMS) value of those differences is 0.83 nanoseconds (ns). The standard deviation of the receiver DCBs estimated by the relative method was smaller than that of the single method. From these results, it is clear that the relative method can obtain more stable receiver DCBs compared with the single method over a short-term period. Additionally, the comparison between the receiver DCBs obtained by the Korea Astronomy and Space Science Institute (KASI) and those of the IGS Global Ionosphere Maps (GIM) showed a good agreement at 0.3 ns. As the accuracy of DCB values significantly affects the accuracy of ionospheric total electron content (TEC), more studies are needed to ensure the reliability and stability of the estimated receiver DCBs.

  13. GPS & GLONASS mass-market receivers: positioning performances and peculiarities.

    PubMed

    Dabove, Paolo; Manzino, Ambrogio M

    2014-01-01

    Over the last twenty years, positioning with low cost Global Navigation Satellite System (GNSS) sensors have rapidly developed around the world at both a commercial and academic research level. For many years these instruments have only acquired the GPS constellation but are now able to track the Global'naja Navigacionnaja Sputnikovaja Sistema (GLONASS) constellation. This characteristic is very interesting, especially if used in hard-urban environments or in hard conditions where satellite visibility is low. The goal of this research is to investigate the contribution of the GLONASS constellation for mass-market receivers in order to analyse the performance in real time (Network Real Time Kinematic-NRTK positioning) with post-processing approaches. Under these conditions, it is possible to confirm that mass-market sensors could be a valid alternative to a more expensive receiver for a large number of surveying applications, but with low cost hardware the contribution of the GLONASS constellation for fixing ambiguities is useless, if not dangerous. PMID:25429405

  14. GPS & GLONASS Mass-Market Receivers: Positioning Performances and Peculiarities

    PubMed Central

    Dabove, Paolo; Manzino, Ambrogio M.

    2014-01-01

    Over the last twenty years, positioning with low cost Global Navigation Satellite System (GNSS) sensors have rapidly developed around the world at both a commercial and academic research level. For many years these instruments have only acquired the GPS constellation but are now able to track the Global’naja Navigacionnaja Sputnikovaja Sistema (GLONASS) constellation. This characteristic is very interesting, especially if used in hard-urban environments or in hard conditions where satellite visibility is low. The goal of this research is to investigate the contribution of the GLONASS constellation for mass-market receivers in order to analyse the performance in real time (Network Real Time Kinematic—NRTK positioning) with post-processing approaches. Under these conditions, it is possible to confirm that mass-market sensors could be a valid alternative to a more expensive receiver for a large number of surveying applications, but with low cost hardware the contribution of the GLONASS constellation for fixing ambiguities is useless, if not dangerous. PMID:25429405

  15. Testing of the International Space Station and X-38 Crew Return Vehicle GPS Receiver

    NASA Technical Reports Server (NTRS)

    Simpson, James; Lightsey, Glenn; Campbell, Chip; Carpenter, Russell; Davis, George; Jackson, Larry; Davis, Ed; Kizhner, Semion

    1999-01-01

    This paper discusses the process and results of the performance testing of the GPS receiver planned for use on the International Space Station (ISS) and the X- 38CrewReturnVehicle(CRV). The receiver is a Force-19 unit manufactured by Trimble Navigation and modified in software by NASA:s Goddard Space Flight Center (GSFC) to perform navigation and attitude determination in space. The receiver is the primary source of navigation and attitude information for ISS and CRV. Engineers at GSFC have developed and tested the new receiver with a Global Simulation Systems Ltd (GSS) GPS Signal Generator (GPSSG). This paper documents the unique aspects of ground testing a GPS receiver that is designed for use in space. A discussion of the design of tests using the GPSSG, documentation, data capture, data analysis, and lessons learned will precede an overview of the performance of the new receiver. A description of the challenges that were overcome during this testing exercise will be presented. Results from testing show that the receiver will be within or near the specifications for ISS attitude and navigation performance. The process for verifying other requirements such as Time to First Fix, Time to First Attitude, selection/deselection of a specific GPS satellite vehicles (SV), minimum signal strength while still obtaining attitude and navigation, navigation and attitude output coverage, GPS week rollover, and Y2K requirements are also given in this paper.

  16. Testing of the International Space Station and X-38 Crew Return Vehicle GPS Receiver

    NASA Technical Reports Server (NTRS)

    Simpson, James; Campbell, Chip; Carpenter, Russell; Davis, Ed; Kizhner, Semion; Lightsey, E. Glenn; Davis, George; Jackson, Larry

    1999-01-01

    This paper discusses the process and results of the performance testing of the GPS receiver planned for use on the International Space Station (ISS) and the X-38 Crew Return Vehicle (CRV). The receiver is a Force-19 unit manufactured by Trimble Navigation and modified in software by the NASA Goddard Space Flight Center (GSFC) to perform navigation and attitude determination in space. The receiver is the primary source of navigation and attitude information for ISS and CRV. Engineers at GSFC have developed and tested the new receiver with a Global Simulation Systems Ltd (GSS) GPS Signal Generator (GPSSG). This paper documents the unique aspects of ground testing a GPS receiver that is designed for use in space. A discussion of the design of tests using the GPSSG, documentation, data capture, data analysis, and lessons learned will precede an overview of the performance of the new receiver. A description of the challenges that were overcome during this testing exercise will be presented. Results from testing show that the receiver will be within or near the specifications for ISS attitude and navigation performance. The process for verifying other requirements such as Time to First Fix, Time to First Attitude, selection/deselection of a specific GPS satellite vehicles (SV), minimum signal strength while still obtaining attitude and navigation, navigation and attitude output coverage, GPS week rollover, and Y2K requirements are also given in this paper.

  17. Testing of the International Space Station and X-38 Crew Return Vehicle GPS Receiver

    NASA Technical Reports Server (NTRS)

    Simpson, James; Campbell, Chip; Carpenter, Russell; Davis, Ed; Kizhner, Semion; Lightsey, E. Glenn; Davis, George; Jackson, Larry

    1999-01-01

    This paper discusses the process and results of the performance testing of the GPS receiver planned for use on the International Space Station (ISS) and the X-38 Crew Return Vehicle (CRV). The receiver is a Force-19 unit manufactured by Trimble Navigation and Modified in software by the NASA Goddard Space Flight Center (GSFC) to perform navigation and attitude determination in space. The receiver is the primary source of navigation and attitude information for ISS and CRV. Engineers at GSFC have developed and tested the new receiver with a Global Simulation Systems Ltd (GSS) GPS Signal Generator (GPSSG). This paper documents the unique aspects of ground testing a GPS receiver that is designed for use in space. A discussion of the design and tests using the GPSSG, documentation, data capture, data analysis, and lessons learned will precede an overview of the performance of the new receiver. A description of the challenges of that were overcome during this testing exercise will be presented. Results from testing show that the receiver will be within or near the specifications for ISS attitude and navigation performance. The process for verifying other requirements such as Time to First Fix, Time to First Attitude, selection/deselection of a specific GPS satellite vehicles (SV), minimum signal strength while still obtaining attitude and navigation, navigation and attitude output coverage, GPS week rollover, and Y2K requirements are also given in this paper.

  18. An alternative method for determining GPS receiver phase biases

    NASA Astrophysics Data System (ADS)

    Kersten, Tobias; Schön, Steffen

    2015-04-01

    Precise Point Positioning (PPP) is used in a broad variety of applications to determine very economically high precision parameters for positioning, navigation and timing. In comparison to traditional differential approaches, PPP with undifferenced phase measurements is highly attractive, since the effort on the user side can be reduced to minimum, e.g. due to an unnecessary reference station. The quality of obtained position solutions is comparable to those obtained from a differential approach. One of the most important limiting factor is the long integration time to determine (float) ambiguities. Furthermore, it is critical to consider adequately all occurring error sources. In this context, receiver phase biases are one of the limiting factors and very complex to model. At least they are highly correlated with the ambiguities during the estimation process, (Laurichesse et al. 2009). This contribution presents an alternative method to estimate carrier phase biases of different GPS/GNSS receivers and signals w.r.t. a reference receiver. Receiver phase biases are estimated on a zero baseline and in combination with a very stable and precise clock (H-Maser) using single differences. The presented method will be discussed in detail. This includes a critical look to the estimability of bias values for several GPS/GNSS receivers as well as a discussion on the stability and universality of these bias values. Finally relative phase biases are quantified and it will be discussed how GPS/GNSS observation equations have to be extended, to take these bias values correctly into account. References: Laurichesse D., Mercier F., Berthias J.P., Broca P., Cerri L. (2009): Integer ambiguity resolution on undifferenced GPS phase measurements and its application to PPP and satellite precise orbit determination, In: NAVIGATION, Journal of the Institute of Navigation, Volume 56, Number 2, pages: 135 - 149

  19. Combined constellations GPS and Galileo systems

    NASA Astrophysics Data System (ADS)

    Januszewski, Jacek

    As for the users of satellite navigation systems the actual slogan is GPS and Galileo the advantages and disadvantages of different combined constellations of these systems must be taken into account. The distributions (in per cent) of the numbers of satellites visible by the observer at different latitudes situated in open and restricted (urban canyon) area for different masking elevation angles (Hmin) for two combined constellations GPS + Galileo systems (I - 29 GPS satellites + 27 Galileo satellites, II - 29 GPS + 30 Galileo) are presented in this paper. In addition to it the detailed distributions for the observer at latitudes 50-60° for other constellations & elevation angles are demonstrated. For the first constellation the difference between the number of GPS satellites visible by the observer above horizon (Hmin = 0°) at latitudes 50-60° and the number of Galileo satellites visible by the same observer at the same time can be equal each number between plus 7 and minus 7. This fact must be taken into account in the production and the determination of the number of channel of GPS-Galileo integrated receivers.

  20. GPS-based system for satellite tracking and geodesy

    NASA Technical Reports Server (NTRS)

    Bertiger, Willy I.; Thornton, Catherine L.

    1989-01-01

    High-performance receivers and data processing systems developed for GPS are reviewed. The GPS Inferred Positioning System (GIPSY) and the Orbiter Analysis and Simulation Software (OASIS) are described. The OASIS software is used to assess GPS system performance using GIPSY for data processing. Consideration is given to parameter estimation for multiday arcs, orbit repeatability, orbit prediction, daily baseline repeatability, agreement with VLBI, and ambiguity resolution. Also, the dual-frequency Rogue receiver, which can track up to eight GPS satellites simultaneously, is discussed.

  1. A Real-Time Capable Software-Defined Receiver Using GPU for Adaptive Anti-Jam GPS Sensors

    PubMed Central

    Seo, Jiwon; Chen, Yu-Hsuan; De Lorenzo, David S.; Lo, Sherman; Enge, Per; Akos, Dennis; Lee, Jiyun

    2011-01-01

    Due to their weak received signal power, Global Positioning System (GPS) signals are vulnerable to radio frequency interference. Adaptive beam and null steering of the gain pattern of a GPS antenna array can significantly increase the resistance of GPS sensors to signal interference and jamming. Since adaptive array processing requires intensive computational power, beamsteering GPS receivers were usually implemented using hardware such as field-programmable gate arrays (FPGAs). However, a software implementation using general-purpose processors is much more desirable because of its flexibility and cost effectiveness. This paper presents a GPS software-defined radio (SDR) with adaptive beamsteering capability for anti-jam applications. The GPS SDR design is based on an optimized desktop parallel processing architecture using a quad-core Central Processing Unit (CPU) coupled with a new generation Graphics Processing Unit (GPU) having massively parallel processors. This GPS SDR demonstrates sufficient computational capability to support a four-element antenna array and future GPS L5 signal processing in real time. After providing the details of our design and optimization schemes for future GPU-based GPS SDR developments, the jamming resistance of our GPS SDR under synthetic wideband jamming is presented. Since the GPS SDR uses commercial-off-the-shelf hardware and processors, it can be easily adopted in civil GPS applications requiring anti-jam capabilities. PMID:22164116

  2. Digital signal processor and processing method for GPS receivers

    NASA Technical Reports Server (NTRS)

    Thomas, Jr., Jess B. (Inventor)

    1989-01-01

    A digital signal processor and processing method therefor for use in receivers of the NAVSTAR/GLOBAL POSITIONING SYSTEM (GPS) employs a digital carrier down-converter, digital code correlator and digital tracking processor. The digital carrier down-converter and code correlator consists of an all-digital, minimum bit implementation that utilizes digital chip and phase advancers, providing exceptional control and accuracy in feedback phase and in feedback delay. Roundoff and commensurability errors can be reduced to extremely small values (e.g., less than 100 nanochips and 100 nanocycles roundoff errors and 0.1 millichip and 1 millicycle commensurability errors). The digital tracking processor bases the fast feedback for phase and for group delay in the C/A, P.sub.1, and P.sub.2 channels on the L.sub.1 C/A carrier phase thereby maintaining lock at lower signal-to-noise ratios, reducing errors in feedback delays, reducing the frequency of cycle slips and in some cases obviating the need for quadrature processing in the P channels. Simple and reliable methods are employed for data bit synchronization, data bit removal and cycle counting. Improved precision in averaged output delay values is provided by carrier-aided data-compression techniques. The signal processor employs purely digital operations in the sense that exactly the same carrier phase and group delay measurements are obtained, to the last decimal place, every time the same sampled data (i.e., exactly the same bits) are processed.

  3. Estimation and analysis of GPS receiver differential code biases using KGN in Korean Peninsula

    NASA Astrophysics Data System (ADS)

    Choi, B. K.; Cho, J. H.; Lee, S. J.

    2011-05-01

    The total electron content (TEC) estimation by the Global Positioning System (GPS) can be seriously affected by the differential code biases (DCB), referred to as inter-frequency biases (IFB), of the satellite and receiver so that an accuracy of GPS-TEC value is dependent on the error of DCBs estimation. In this paper, we proposed the singular value decomposition (SVD) method to estimate the DCB of GPS satellites and receivers using the Korean GPS network (KGN) in South Korea. The receiver DCBs of about 49 GPS reference stations in KGN were determined for the accurate estimation of the regional ionospheric TEC. They obtained from the daily solution have large biases ranging from +5 to +27 ns for geomagnetic quiet days. The receiver DCB of SUWN reference station was compared with the estimates of IGS and JPL global ionosphere map (GIM). The results have shown comparatively good agreement at the level within 0.2 ns. After correction of receiver DCBs and knowing the satellite DCBs, the comparison between the behavior of the estimated TEC and that of GIMs was performed for consecutive three days. We showed that there is a good agreement between KASI model and GIMs.

  4. GPS/GLONASS Combined Precise Point Positioning with Receiver Clock Modeling

    PubMed Central

    Wang, Fuhong; Chen, Xinghan; Guo, Fei

    2015-01-01

    Research has demonstrated that receiver clock modeling can reduce the correlation coefficients among the parameters of receiver clock bias, station height and zenith tropospheric delay. This paper introduces the receiver clock modeling to GPS/GLONASS combined precise point positioning (PPP), aiming to better separate the receiver clock bias and station coordinates and therefore improve positioning accuracy. Firstly, the basic mathematic models including the GPS/GLONASS observation equations, stochastic model, and receiver clock model are briefly introduced. Then datasets from several IGS stations equipped with high-stability atomic clocks are used for kinematic PPP tests. To investigate the performance of PPP, including the positioning accuracy and convergence time, a week of (1–7 January 2014) GPS/GLONASS data retrieved from these IGS stations are processed with different schemes. The results indicate that the positioning accuracy as well as convergence time can benefit from the receiver clock modeling. This is particularly pronounced for the vertical component. Statistic RMSs show that the average improvement of three-dimensional positioning accuracy reaches up to 30%–40%. Sometimes, it even reaches over 60% for specific stations. Compared to the GPS-only PPP, solutions of the GPS/GLONASS combined PPP are much better no matter if the receiver clock offsets are modeled or not, indicating that the positioning accuracy and reliability are significantly improved with the additional GLONASS satellites in the case of insufficient number of GPS satellites or poor geometry conditions. In addition to the receiver clock modeling, the impacts of different inter-system timing bias (ISB) models are investigated. For the case of a sufficient number of satellites with fairly good geometry, the PPP performances are not seriously affected by the ISB model due to the low correlation between the ISB and the other parameters. However, the refinement of ISB model weakens the

  5. GPS/GLONASS Combined Precise Point Positioning with Receiver Clock Modeling.

    PubMed

    Wang, Fuhong; Chen, Xinghan; Guo, Fei

    2015-01-01

    Research has demonstrated that receiver clock modeling can reduce the correlation coefficients among the parameters of receiver clock bias, station height and zenith tropospheric delay. This paper introduces the receiver clock modeling to GPS/GLONASS combined precise point positioning (PPP), aiming to better separate the receiver clock bias and station coordinates and therefore improve positioning accuracy. Firstly, the basic mathematic models including the GPS/GLONASS observation equations, stochastic model, and receiver clock model are briefly introduced. Then datasets from several IGS stations equipped with high-stability atomic clocks are used for kinematic PPP tests. To investigate the performance of PPP, including the positioning accuracy and convergence time, a week of (1-7 January 2014) GPS/GLONASS data retrieved from these IGS stations are processed with different schemes. The results indicate that the positioning accuracy as well as convergence time can benefit from the receiver clock modeling. This is particularly pronounced for the vertical component. Statistic RMSs show that the average improvement of three-dimensional positioning accuracy reaches up to 30%-40%. Sometimes, it even reaches over 60% for specific stations. Compared to the GPS-only PPP, solutions of the GPS/GLONASS combined PPP are much better no matter if the receiver clock offsets are modeled or not, indicating that the positioning accuracy and reliability are significantly improved with the additional GLONASS satellites in the case of insufficient number of GPS satellites or poor geometry conditions. In addition to the receiver clock modeling, the impacts of different inter-system timing bias (ISB) models are investigated. For the case of a sufficient number of satellites with fairly good geometry, the PPP performances are not seriously affected by the ISB model due to the low correlation between the ISB and the other parameters. However, the refinement of ISB model weakens the

  6. Functional description of signal processing in the Rogue GPS receiver

    NASA Technical Reports Server (NTRS)

    Thomas, J. B.

    1988-01-01

    Over the past year, two Rogue GPS prototype receivers have been assembled and successfully subjected to a variety of laboratory and field tests. A functional description is presented of signal processing in the Rogue receiver, tracing the signal from RF input to the output values of group delay, phase, and data bits. The receiver can track up to eight satellites, without time multiplexing among satellites or channels, simultaneously measuring both group delay and phase for each of three channels (L1-C/A, L1-P, L2-P). The Rogue signal processing described requires generation of the code for all three channels. Receiver functional design, which emphasized accuracy, reliability, flexibility, and dynamic capability, is summarized. A detailed functional description of signal processing is presented, including C/A-channel and P-channel processing, carrier-aided averaging of group delays, checks for cycle slips, acquistion, and distinctive features.

  7. Performance Assessment of Two GPS Receivers on Space Shuttle

    NASA Technical Reports Server (NTRS)

    Schroeder, Christine A.; Schutz, Bob E.

    1996-01-01

    Space Shuttle STS-69 was launched on September 7, 1995, carrying the Wake Shield Facility (WSF-02) among its payloads. The mission included two GPS receivers: a Collins 3M receiver onboard the Endeavour and an Osborne flight TurboRogue, known as the TurboStar, onboard the WSF-02. Two of the WSF-02 GPS Experiment objectives were to: (1) assess the ability to use GPS in a relative satellite positioning mode using the receivers on Endeavour and WSF-02; and (2) assess the performance of the receivers to support high precision orbit determination at the 400 km altitude. Three ground tests of the receivers were conducted in order to characterize the respective receivers. The analysis of the tests utilized the Double Differencing technique. A similar test in orbit was conducted during STS-69 while the WSF-02 was held by the Endeavour robot arm for a one hour period. In these tests, biases were observed in the double difference pseudorange measurements, implying that biases up to 140 m exist which do not cancel in double differencing. These biases appear to exist in the Collins receiver, but their effect can be mitigated by including measurement bias parameters to accommodate them in an estimation process. An additional test was conducted in which the orbit of the combined Endeavour/WSF-02 was determined independently with each receiver. These one hour arcs were based on forming double differences with 13 TurboRogue receivers in the global IGS network and estimating pseudorange biases for the Collins. Various analyses suggest the TurboStar overall orbit accuracy is about one to two meters for this period, based on double differenced phase residuals of 34 cm. These residuals indicate the level of unmodeled forces on Endeavour produced by gravitational and nongravitational effects. The rms differences between the two independently determined orbits are better than 10 meters, thereby demonstrating the accuracy of the Collins-determined orbit at this level as well as the

  8. GENESIS: GPS Environmental and Earth Science Information System

    NASA Technical Reports Server (NTRS)

    Hajj, George

    1999-01-01

    This presentation reviews the GPS ENvironmental and Earth Science Information System (GENESIS). The objectives of GENESIS are outlined (1) Data Archiving, searching and distribution for science data products derived from Space borne TurboRogue Space Receivers for GPS science and other ground based GPS receivers, (2) Data browsing using integrated visualization tools, (3) Interactive web/java-based data search and retrieval, (4) Data subscription service, (5) Data migration from existing GPS archived data, (6) On-line help and documentation, and (7) participation in the WP-ESIP federation. The presentation reviews the products and services of Genesis, and the technology behind the system.

  9. A New Indoor Positioning System Architecture Using GPS Signals

    PubMed Central

    Xu, Rui; Chen, Wu; Xu, Ying; Ji, Shengyue

    2015-01-01

    The pseudolite system is a good alternative for indoor positioning systems due to its large coverage area and accurate positioning solution. However, for common Global Positioning System (GPS) receivers, the pseudolite system requires some modifications of the user terminals. To solve the problem, this paper proposes a new pseudolite-based indoor positioning system architecture. The main idea is to receive real-world GPS signals, repeat each satellite signal and transmit those using indoor transmitting antennas. The transmitted GPS-like signal can be processed (signal acquisition and tracking, navigation data decoding) by the general receiver and thus no hardware-level modification on the receiver is required. In addition, all Tx can be synchronized with each other since one single clock is used in Rx/Tx. The proposed system is simulated using a software GPS receiver. The simulation results show the indoor positioning system is able to provide high accurate horizontal positioning in both static and dynamic situations. PMID:25938199

  10. A New Indoor Positioning System Architecture Using GPS Signals.

    PubMed

    Xu, Rui; Chen, Wu; Xu, Ying; Ji, Shengyue

    2015-01-01

    The pseudolite system is a good alternative for indoor positioning systems due to its large coverage area and accurate positioning solution. However, for common Global Positioning System (GPS) receivers, the pseudolite system requires some modifications of the user terminals. To solve the problem, this paper proposes a new pseudolite-based indoor positioning system architecture. The main idea is to receive real-world GPS signals, repeat each satellite signal and transmit those using indoor transmitting antennas. The transmitted GPS-like signal can be processed (signal acquisition and tracking, navigation data decoding) by the general receiver and thus no hardware-level modification on the receiver is required. In addition, all Tx can be synchronized with each other since one single clock is used in Rx/Tx. The proposed system is simulated using a software GPS receiver. The simulation results show the indoor positioning system is able to provide high accurate horizontal positioning in both static and dynamic situations. PMID:25938199

  11. DYNAMIC TESTING OF GPS RECEIVERS ON AGRICULTURAL AIRCRAFT FOR REMOTE SENSING AND VARIABLE-RATE AERIAL APPLICATION

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Global Positioning System (GPS) receivers and GPS-based swath guidance systems are used on agricultural aircraft for remote sensing, airplane guidance, and to support variable-rate aerial application of crop inputs such as insecticides, cotton growth regulators, and defoliants. Agricultural aircraf...

  12. Research on Signal Processing Algorithms in GPS Receivers

    NASA Astrophysics Data System (ADS)

    Cai, Fan; Yin, Yan; Zhang, Xiu-Zhong

    2007-03-01

    The modern standard satellite navigation receivers are commonly based on ASICs for signal processing and fast microprocessors for application calculations. The software satellite navigation receiver is also developed in recent years. The research on software receivers becomes one trend of satellite navigation receiver. For algorithms on signal processing play an important role in satellite navigation receivers, the paper illuminates the signal processing algorithms in detail. The GPS receiver is widely used at present. So the paper places emphasis on signal processing algorithms about GPS receiver. Signal processing algorithms include three aspects: the algorithm on signal acquisition, the algorithm on carrier tracking and the algorithm on PRN (pseudo random noise) code tracking. In the part of signal acquisition, the method of using FFT to get the result of circular correlation is introduced. The paper carefully researches the method and discusses the derivation process of the method. In the part of carrier tracking, the paper describes the principle of frequency locked loop (FLL) and phase locked loop (PLL) and analyzes the principle of loop filter. The method of transition from s-domain to z-domain is introduced. The computation of noise bandwidth of the loop filter are expatiated and the structures of one-step digital loop filter, two-step digital loop filter and three step are given. Other parameters of loop filters are also given. In the part of code tracking, delay-early locked loop (DLL) is introduced. Theoretical analysis and experiment results demonstrate the algorithms in the paper. Through the simulation testing, the performance of combination of PLL and FLL can be acknowledged.

  13. Global Positioning System receiver evaluation results

    SciTech Connect

    Byrne, R.H.

    1993-09-01

    A Sandia project currently uses an outdated Magnavox 6400 Global Positioning System (GPS) receiver as the core of its navigation system. The goal of this study was to analyze the performance of the current GPS receiver compared to newer, less expensive models and to make recommendations on how to improve the performance of the overall navigation system. This paper discusses the test methodology used to experimentally analyze the performance of different GPS receivers, the test results, and recommendations on how an upgrade should proceed. Appendices contain detailed information regarding the raw data, test hardware, and test software.

  14. Evaluating the Effect of Global Positioning System (GPS) Satellite Clock Error via GPS Simulation

    NASA Astrophysics Data System (ADS)

    Sathyamoorthy, Dinesh; Shafii, Shalini; Amin, Zainal Fitry M.; Jusoh, Asmariah; Zainun Ali, Siti

    2016-06-01

    This study is aimed at evaluating the effect of Global Positioning System (GPS) satellite clock error using GPS simulation. Two conditions of tests are used; Case 1: All the GPS satellites have clock errors within the normal range of 0 to 7 ns, corresponding to pseudorange error range of 0 to 2.1 m; Case 2: One GPS satellite suffers from critical failure, resulting in clock error in the pseudorange of up to 1 km. It is found that increase of GPS satellite clock error causes increase of average positional error due to increase of pseudorange error in the GPS satellite signals, which results in increasing error in the coordinates computed by the GPS receiver. Varying average positional error patterns are observed for the each of the readings. This is due to the GPS satellite constellation being dynamic, causing varying GPS satellite geometry over location and time, resulting in GPS accuracy being location / time dependent. For Case 1, in general, the highest average positional error values are observed for readings with the highest PDOP values, while the lowest average positional error values are observed for readings with the lowest PDOP values. For Case 2, no correlation is observed between the average positional error values and PDOP, indicating that the error generated is random.

  15. Receiver autonomous integrity monitoring using a 24-satellite GPS constellation

    NASA Astrophysics Data System (ADS)

    Brown, Alison K.

    A 24-satellite GPS configuration is studied in order to explore the conditions under which both failure detection and isolation are possible using receiver autonomous integrity monitoring (RAIM). Simulation results show that the satellite coverage provided by both the 3-plane and the 6-plane constellations considered are suitable to provide integrity for all phases of flight except for nonprecision approaches. Although the 6-plane constellation has marginally poorer geometry for satellite failure detection than the 3-plane constellation, the average satellite isolation geometry is significantly better, making the 6-plane constellation preferable for RAIM.

  16. Simulation of a navigator algorithm for a low-cost GPS receiver

    NASA Technical Reports Server (NTRS)

    Hodge, W. F.

    1980-01-01

    The analytical structure of an existing navigator algorithm for a low cost global positioning system receiver is described in detail to facilitate its implementation on in-house digital computers and real-time simulators. The material presented includes a simulation of GPS pseudorange measurements, based on a two-body representation of the NAVSTAR spacecraft orbits, and a four component model of the receiver bias errors. A simpler test for loss of pseudorange measurements due to spacecraft shielding is also noted.

  17. GPS/GLONASS Time Transfer with 20-Channel Dual GNSS Receiver

    NASA Technical Reports Server (NTRS)

    Daly, P.; Riley, S.

    1996-01-01

    One of the world's two global navigation systems, the Global Positioning System (GPS), is already fully operational (April 1994) and the other, the Global Navigation Satellite System (GLONASS) will become operational by the end of 1995 or early 1996. Each will offer, independently of the other, precise location and time transfer continuously anywhere in the world and indeed in space itself. Many potential users, in particular the civil aviation community, are keenly interested in a joint GPS/GLONASS operation since it would offer substantial advantages in defining and maintaining the integrity of the navigation aid. Results are presented on the characterization of GPS/GLONASS time comparison using a 20-channel dual receiver developed and constructed at the University of Leeds, UK.

  18. Initial GPS scintillation results from CASES receiver at South Pole, Antarctica

    NASA Astrophysics Data System (ADS)

    Deshpande, K. B.; Bust, G. S.; Clauer, C. R.; Kim, H.; Macon, J. E.; Humphreys, T. E.; Bhatti, J. A.; Musko, S. B.; Crowley, G.; Weatherwax, A. T.

    2012-10-01

    Connected Autonomous Space Environment Sensor (CASES) Global Positioning System (GPS) software-defined receivers developed for ionospheric scintillation studies have been deployed on Autonomous Adaptive Low-Power Instrument Platforms (AAL-PIP) at South Pole, Antarctica. In this paper, we describe the AAL-PIP experimental setup focusing on CASES. We explain in detail the method developed for analyzing CASES data, and report initial AAL-PIP CASES results. Furthermore, we compare the CASES measurements with those from a modified Novatel GSV4004 GPS Ionospheric Scintillations and TEC Monitor (GISTM) receiver at the South Pole. CASES receivers have been successfully deployed and reliably operated in equatorial and midlatitude regions. Four of these GPS receivers, for the first time, are deployed in high-latitude regions as a part of the National Science Foundation (NSF) funded project of deploying space science instrument platforms, AAL-PIPs, in Antarctica since December 2010-2011. We present initial scintillation results recorded by a CASES receiver at South Pole during the storm on 24 January 2012 along with AAL-PIP magnetometer observations. We have deduced that the CASES receiver scintillation observations agree with those from the Novatel GPS scintillation receiver. Since this is the first time a CASES receiver has been deployed to operate in a high latitude, low temperature, and low humidity environment, we consider this comparison a demonstration of its reliable operation as a science-grade scintillation receiver in such conditions. We plan to study high latitude ionospheric irregularities by using observations from CASES and other ancillary instruments from Antarctica coupled with physical parameters derived from models.

  19. Relative Attitude Determination of Earth Orbiting Formations Using GPS Receivers

    NASA Technical Reports Server (NTRS)

    Lightsey, E. Glenn

    2004-01-01

    Satellite formation missions require the precise determination of both the position and attitude of multiple vehicles to achieve the desired objectives. In order to support the mission requirements for these applications, it is necessary to develop techniques for representing and controlling the attitude of formations of vehicles. A generalized method for representing the attitude of a formation of vehicles has been developed. The representation may be applied to both absolute and relative formation attitude control problems. The technique is able to accommodate formations of arbitrarily large number of vehicles. To demonstrate the formation attitude problem, the method is applied to the attitude determination of a simple leader-follower along-track orbit formation. A multiplicative extended Kalman filter is employed to estimate vehicle attitude. In a simulation study using GPS receivers as the attitude sensors, the relative attitude between vehicles in the formation is determined 3 times more accurately than the absolute attitude.

  20. Flight Performance Evaluation of Three GPS Receivers for Sounding Rocket Tracking

    NASA Technical Reports Server (NTRS)

    Bull, Barton; Diehl, James; Montenbruck, Oliver; Markgraf, Markus; Bauer, Frank (Technical Monitor)

    2001-01-01

    In preparation for the European Space Agency Maxus-4 mission, a sounding rocket test flight was carried out at Esrange,, near Kiruna, Sweden on February 19, 2001 to validate existing ground facilities and range safety installations. Due to the absence of a dedicated scientific payload, the flight offered the opportunity to test multiple GPS receivers and assess their performance for the tracking of sounding rockets. The receivers included an Ashtech G12 HDMA receiver, a BAE (Canadian Marconi) Allstar receiver and a Mitel Orion receiver. All of them provide CIA code tracking on the L1 frequency to determine the user position and make use of Doppler measurements to derive the instantaneous velocity. Among the receivers, the G12 has been optimized for use under highly dynamic conditions and has earlier been flown successfully on NASA sounding rockets [Bull, ION-GPS-2000]. The Allstar is representative of common single frequency receivers for terrestrial applications and received no particular modification, except for the disabling of the common altitude and velocity constraints that would otherwise inhibit its use for space application. The Orion receiver, finally, employs the same Mitel chipset as the Allstar, but has received various firmware modifications by DLR to safeguard it against signal losses and improve its tracking performance [Montenbruck et al., ION-GPS-2000]. While the two NASA receivers were driven by a common wrap-around antenna, the DLR experiment made use of a switchable antenna system comprising a helical antenna in the tip of the rocket and two blade antennas attached to the body of the vehicle. During the boost a peak acceleration of roughly 17g's was achieved which resulted in a velocity of about 1100 m/s at the end of the burn. At apogee, the rocket reached a maximum altitude of over 80 km. A detailed analysis of the attained flight data will be given in the paper together with a evaluation of different receiver designs and antenna concepts.

  1. Shuttle Global Positioning (GPS) System design study

    NASA Technical Reports Server (NTRS)

    Nilsen, P.; Huth, G. K.

    1980-01-01

    Investigations of certain aspects and problems of the shuttle global positioning system GPS, are presented. Included are: test philosophy and test outline; development of a phase slope specification for the shuttle GPS antenna; an investigation of the shuttle jamming vulnerability; and an expression for the GPS signal to noise density ratio for the thermal protection system.

  2. The Performance Analysis of a Real-Time Integrated INS/GPS Vehicle Navigation System with Abnormal GPS Measurement Elimination

    PubMed Central

    Chiang, Kai-Wei; Duong, Thanh Trung; Liao, Jhen-Kai

    2013-01-01

    The integration of an Inertial Navigation System (INS) and the Global Positioning System (GPS) is common in mobile mapping and navigation applications to seamlessly determine the position, velocity, and orientation of the mobile platform. In most INS/GPS integrated architectures, the GPS is considered to be an accurate reference with which to correct for the systematic errors of the inertial sensors, which are composed of biases, scale factors and drift. However, the GPS receiver may produce abnormal pseudo-range errors mainly caused by ionospheric delay, tropospheric delay and the multipath effect. These errors degrade the overall position accuracy of an integrated system that uses conventional INS/GPS integration strategies such as loosely coupled (LC) and tightly coupled (TC) schemes. Conventional tightly coupled INS/GPS integration schemes apply the Klobuchar model and the Hopfield model to reduce pseudo-range delays caused by ionospheric delay and tropospheric delay, respectively, but do not address the multipath problem. However, the multipath effect (from reflected GPS signals) affects the position error far more significantly in a consumer-grade GPS receiver than in an expensive, geodetic-grade GPS receiver. To avoid this problem, a new integrated INS/GPS architecture is proposed. The proposed method is described and applied in a real-time integrated system with two integration strategies, namely, loosely coupled and tightly coupled schemes, respectively. To verify the effectiveness of the proposed method, field tests with various scenarios are conducted and the results are compared with a reliable reference system. PMID:23955434

  3. The performance analysis of a real-time integrated INS/GPS vehicle navigation system with abnormal GPS measurement elimination.

    PubMed

    Chiang, Kai-Wei; Duong, Thanh Trung; Liao, Jhen-Kai

    2013-01-01

    The integration of an Inertial Navigation System (INS) and the Global Positioning System (GPS) is common in mobile mapping and navigation applications to seamlessly determine the position, velocity, and orientation of the mobile platform. In most INS/GPS integrated architectures, the GPS is considered to be an accurate reference with which to correct for the systematic errors of the inertial sensors, which are composed of biases, scale factors and drift. However, the GPS receiver may produce abnormal pseudo-range errors mainly caused by ionospheric delay, tropospheric delay and the multipath effect. These errors degrade the overall position accuracy of an integrated system that uses conventional INS/GPS integration strategies such as loosely coupled (LC) and tightly coupled (TC) schemes. Conventional tightly coupled INS/GPS integration schemes apply the Klobuchar model and the Hopfield model to reduce pseudo-range delays caused by ionospheric delay and tropospheric delay, respectively, but do not address the multipath problem. However, the multipath effect (from reflected GPS signals) affects the position error far more significantly in a consumer-grade GPS receiver than in an expensive, geodetic-grade GPS receiver. To avoid this problem, a new integrated INS/GPS architecture is proposed. The proposed method is described and applied in a real-time integrated system with two integration strategies, namely, loosely coupled and tightly coupled schemes, respectively. To verify the effectiveness of the proposed method, field tests with various scenarios are conducted and the results are compared with a reliable reference system. PMID:23955434

  4. Civil Application of Differential GPS Using a Single Channel Sequential Receiver

    NASA Technical Reports Server (NTRS)

    1981-01-01

    The Global Positioning System (GPS) and its potential for area navigation, landing, and takeoff under minimum ceilings and advanced air traffic control operation is discussed. The following topics are reported: status of the GPS system; GPS signal availability for the civil community; alternative differential GPS concepts; predicted performance enhancement achievable with differential GPS and the operational improvements which will result; and a development program to test and evaluate differential GPS concepts, performance and operational procedures applicable to helicopters. Potential benefits which will be derived from helicopter use of GPS in the differential mode are identified.

  5. 47 CFR 87.151 - Special requirements for differential GPS receivers.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 5 2012-10-01 2012-10-01 false Special requirements for differential GPS receivers. 87.151 Section 87.151 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND... differential GPS receivers. (a) The receiver shall achieve a message failure rate less than or equal to...

  6. 47 CFR 87.151 - Special requirements for differential GPS receivers.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 5 2011-10-01 2011-10-01 false Special requirements for differential GPS receivers. 87.151 Section 87.151 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND... differential GPS receivers. (a) The receiver shall achieve a message failure rate less than or equal to...

  7. 47 CFR 87.151 - Special requirements for differential GPS receivers.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 5 2014-10-01 2014-10-01 false Special requirements for differential GPS receivers. 87.151 Section 87.151 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND... differential GPS receivers. (a) The receiver shall achieve a message failure rate less than or equal to...

  8. 47 CFR 87.151 - Special requirements for differential GPS receivers.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 5 2010-10-01 2010-10-01 false Special requirements for differential GPS receivers. 87.151 Section 87.151 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND... differential GPS receivers. (a) The receiver shall achieve a message failure rate less than or equal to...

  9. 47 CFR 87.151 - Special requirements for differential GPS receivers.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 5 2013-10-01 2013-10-01 false Special requirements for differential GPS receivers. 87.151 Section 87.151 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND... differential GPS receivers. (a) The receiver shall achieve a message failure rate less than or equal to...

  10. Real-time GPS seismology using a single receiver: method comparison, error analysis and precision validation

    NASA Astrophysics Data System (ADS)

    Li, Xingxing

    2014-05-01

    Earthquake monitoring and early warning system for hazard assessment and mitigation has traditional been based on seismic instruments. However, for large seismic events, it is difficult for traditional seismic instruments to produce accurate and reliable displacements because of the saturation of broadband seismometers and problematic integration of strong-motion data. Compared with the traditional seismic instruments, GPS can measure arbitrarily large dynamic displacements without saturation, making them particularly valuable in case of large earthquakes and tsunamis. GPS relative positioning approach is usually adopted to estimate seismic displacements since centimeter-level accuracy can be achieved in real-time by processing double-differenced carrier-phase observables. However, relative positioning method requires a local reference station, which might itself be displaced during a large seismic event, resulting in misleading GPS analysis results. Meanwhile, the relative/network approach is time-consuming, particularly difficult for the simultaneous and real-time analysis of GPS data from hundreds or thousands of ground stations. In recent years, several single-receiver approaches for real-time GPS seismology, which can overcome the reference station problem of the relative positioning approach, have been successfully developed and applied to GPS seismology. One available method is real-time precise point positioning (PPP) relied on precise satellite orbit and clock products. However, real-time PPP needs a long (re)convergence period, of about thirty minutes, to resolve integer phase ambiguities and achieve centimeter-level accuracy. In comparison with PPP, Colosimo et al. (2011) proposed a variometric approach to determine the change of position between two adjacent epochs, and then displacements are obtained by a single integration of the delta positions. This approach does not suffer from convergence process, but the single integration from delta positions to

  11. Integrated Global Positioning Systems (GPS) Laboratory

    NASA Technical Reports Server (NTRS)

    Brown, Dewayne Randolph

    2002-01-01

    The purpose of this research is to develop a user-friendly Integrated GPS lab manual. This manual will help range engineers at NASA to integrate the use of GPS Simulators, GPS receivers, computers, MATLAB software, FUGAWI software and SATELLITE TOOL KIT software. The lab manual will be used in an effort to help NASA engineers predict GPS Coverage of planned operations and analyze GPS coverage of operation post mission. The Integrated GPS Laboratory was used to do GPS Coverage for two extensive case studies. The first scenario was an airplane trajectory in which an aircraft flew from Cape Canaveral to Los Angeles, California. In the second scenario, a rocket trajectory was done whereas a rocket was launched from Cape Canaveral to one thousand kilometers due east in the Atlantic Ocean.

  12. Signal quality monitoring for GPS augmentation systems

    NASA Astrophysics Data System (ADS)

    Mitelman, Alexander Michael

    Civilian applications of the Global Positioning System have grown rapidly over the past decade. One of the most significant examples is guidance for aviation. In conjunction with specially designed equipment on the ground, GPS can provide precision approach and landing capability for aircraft. As with other safety-critical aviation applications, GPS-based landing systems must meet stringent accuracy, safety, and availability requirements set by the Federal Aviation Administration. Currently, compliance with FAA requirements is ensured by a host of monitors including the Signal Quality Monitor, a module specifically tasked with continuously observing raw GPS signals for interference and distortion. This dissertation focuses on several theoretical and practical aspects of SQM design. The discussion begins with in-depth analysis of the seminal event in SQM, a significant anomaly on GPS space vehicle 19 initially observed in 1993. At the time, a tenfold increase in vertical position error was reported when this satellite was in view. Little consensus was initially reached about the exact origin, nature, or magnitude of the distortion; this section considers these effects in detail. The analysis is then extended to compute a rigorous upper bound for differential error. Starting with the architecture of a basic landing system, a theoretical worst-case is derived that maximizes user error while defying detection by the ground station. A simplified distortion model, adopted by the International Civil Aviation Organization in response to the worst-case analysis, is also described. The discussion then describes the design and construction of an arbitrary GPS generator. Essential features include architecture, shielding, independent signal and noise levels, and fast switching between two input channels. Two example applications are presented to illustrate the instrument's utility. A theoretical analysis of the ICAO model is validated by measuring the spectra of generated

  13. A Pseudolite-Based Positioning System for Legacy GNSS Receivers

    PubMed Central

    Kim, Chongwon; So, Hyoungmin; Lee, Taikjin; Kee, Changdon

    2014-01-01

    The ephemeris data format of legacy GPS receivers is improper for positioning stationary pseudolites on the ground. Therefore, to utilize pseudolites for navigation, GPS receivers must be modified so that they can handle the modified data formats of the pseudolites. Because of this problem, the practical use of pseudolites has so far been limited. This paper proposes a pseudolite-based positioning system that can be used with unmodified legacy GPS receivers. In the proposed system, pseudolites transmit simulated GPS signals. The signals use standard GPS ephemeris data format and contain ephemeris data of simulated GPS satellites, not those of pseudolites. The use of the standard format enables the GPS receiver to process pseudolite signals without any modification. However, the position output of the GPS receiver is not the correct position in this system, because there are additional signal delays from each pseudolite to the receiver. A post-calculation process was added to obtain the correct receiver position using GPS receiver output. This re-estimation is possible because it is based on known information about the simulated signals, pseudolites, and positioning process of the GPS receiver. Simulations using generated data and live GPS data are conducted for various geometries to verify the proposed system. The test results show that the proposed system provides the desired user position using pseudolite signals without requiring any modifications to the legacy GPS receiver. In this initial study, a pseudolite-only indoor system was assumed. However, it can be expanded to a GPS-pseudolite system outdoors. PMID:24681674

  14. A pseudolite-based positioning system for legacy GNSS receivers.

    PubMed

    Kim, Chongwon; So, Hyoungmin; Lee, Taikjin; Kee, Changdon

    2014-01-01

    The ephemeris data format of legacy GPS receivers is improper for positioning stationary pseudolites on the ground. Therefore, to utilize pseudolites for navigation, GPS receivers must be modified so that they can handle the modified data formats of the pseudolites. Because of this problem, the practical use of pseudolites has so far been limited. This paper proposes a pseudolite-based positioning system that can be used with unmodified legacy GPS receivers. In the proposed system, pseudolites transmit simulated GPS signals. The signals use standard GPS ephemeris data format and contain ephemeris data of simulated GPS satellites, not those of pseudolites. The use of the standard format enables the GPS receiver to process pseudolite signals without any modification. However, the position output of the GPS receiver is not the correct position in this system, because there are additional signal delays from each pseudolite to the receiver. A post-calculation process was added to obtain the correct receiver position using GPS receiver output. This re-estimation is possible because it is based on known information about the simulated signals, pseudolites, and positioning process of the GPS receiver. Simulations using generated data and live GPS data are conducted for various geometries to verify the proposed system. The test results show that the proposed system provides the desired user position using pseudolite signals without requiring any modifications to the legacy GPS receiver. In this initial study, a pseudolite-only indoor system was assumed. However, it can be expanded to a GPS-pseudolite system outdoors. PMID:24681674

  15. GPS-based certification for the microwave landing system

    NASA Technical Reports Server (NTRS)

    Thornton, C. L.; Young, L. E.; Wu, S. C.; Thomas, J. B.

    1984-01-01

    An MLS (microwave landing system) certification system based on the Global Positioning System (GPS) is described. To determine the position history of the flight inspection aircraft during runway approach, signals from the GPS satellites, together with on-board radar altimetry, are used. It is shown that the aircraft position relative to a fixed point on the runway at threshold can be determined to about 30 cm vertically and 1 m horizontally. A requirement of the system is that the GPS receivers be placed on each flight inspection aircraft and at selected ground sites. The effects of different error sources on the determination of aircraft instantaneous position and its dynamics are analyzed.

  16. Radiation characterization report for the GPS Receiver microcontroller chip

    NASA Astrophysics Data System (ADS)

    1994-06-01

    The overall objective of this characterization test was to determine the sensitivity of the Motorola 68332 32-bit microcontroller to radiation induced single event upset and latch-up (SEU/SEL). The microcontroller is a key component of the GPS Receiver which will be a subsystem of the satellite required for the 'FORTE' experiment. Testing was conducted at the Single Event Effects Laboratory at Brookhaven National Laboratory. The results obtained included a latch-up (SEL) threshold LET (Linear Energy Transfer) of 20 MeV-sq cm/mg and an upset (SEU) threshold LET of 5 MeV-sq cm/mg. The SEU threshold is typical of this technology, commercial 0.8 micrometers HCMOS. Some flow errors were observed that were not reset by the internal watchdog timer of the 68332. It is important that the Receiver design include a monitor of the device, such as an external watch-dog timer, that would initiate a reset of the program when this type of upset occurs. The SEL threshold is lower than would be expected for this 12 micrometer epi layer process and suggests the need for a strategy that would allow for a hard reset of the controller when a latch-up event occurs. Analysis of the galactic cosmic ray spectrum for the FORTE orbit was done and the results indicate a worst case latch-up rate for this device of 6.3 x 10(exp -5) latch-ups per device day or roughly one latch-up per 43.5 device years.

  17. New approaches for tracking earth orbiters using modified GPS ground receivers

    NASA Technical Reports Server (NTRS)

    Lichten, S. M.; Young, L. E.; Nandi, S.; Haines, B. J.; Dunn, C. E.; Edwards, C. D.

    1993-01-01

    A Global Positioning System (GPS) flight receiver provides a means to precisely determine orbits for satellites in low to moderate altitude orbits. Above a 5000-km altitude, however, relatively few GPS satellites are visible. New approaches to orbit determination for satellites at higher altitudes could reduce DSN antenna time needed to provide navigation and orbit determination support to future missions. Modification of GPS ground receivers enables a beacon from the orbiter to be tracked simultaneously with GPS data. The orbit accuracy expected from this GPS-like tracking (GLT) technique is expected to be in the range of a few meters or better for altitudes up to 100,000 km with a global ground network. For geosynchronous satellites, however, there are unique challenges due to geometrical limitations and to the lack of strong dynamical signature in tracking data. We examine two approaches for tracking the Tracking and Data Relay Satellite System (TDRSS) geostationary orbiters. One uses GLT with a global network; the other relies on a small 'connected element' ground network with a distributed clock for short-baseline differential carrier phase (SB Delta Phi). We describe an experiment planned for late 1993, which will combine aspects of both GLT and SB Delta Phi, to demonstrate a new approach for tracking the Tracking and Data Relay Satellites (TDRSs) that offers a number of operationally convenient and attractive features. The TDRS demonstration will be in effect a proof-of-concept experiment for a new approach to tracking spacecraft which could be applied more generally to deep-space as well as near-Earth regimes.

  18. The use of the AOA TTR-4P GPS receiver in operation at the BIPM for real-time restitution of GPS time

    NASA Technical Reports Server (NTRS)

    Thomas, Claudine

    1994-01-01

    The Global Positioning System is an outstanding tool for the dissemination of time. Using mono-channel C/A-code GPS time receivers, the restitution of GPS time through the satellite constellation presents a peak-to-peak discrepancy of several tens of nanoseconds without SA but may be as high as several hundreds of nanoseconds with SA. As a consequence, civil users are more and more interested in implementing hardware and software methods for efficient restitution of GPS time, especially in the framework of the project of a real-time prediction of UTC (UTCp) which could be available in the form of time differences (UTCp - GPS time). Previous work, for improving the real-time restitution of GPS time with SA, to the level obtained without SA, focused on the implementation of a Kalman filter based on past data and updated at each new observation. An alternative solution relies upon the statistical features of the noise brought about by SA; it has already been shown that the SA noise is efficiently reduced by averaging data from numerous satellites observed simultaneously over a sufficiently long time. This method was successfully applied to data from a GPS time receiver, model AOA TTR-4P, connected to the cesium clock kept at the BIPM. This device, a multi-channel, dual frequency, P-code GPS time receiver, is one of the first TTR-4P units in operation in a civil laboratory. Preliminary comparative studies of this new equipment with conventional GPS time receivers are described in this paper. The results of an experimental restitution of GPS time, obtained in June 1993, are also detailed: 3 to 6 satellites were observed simultaneously with a sample interval of 15 s, an efficient smoothing of SA noise was realized by averaging data on all observed satellites over more than 1 hour. When the GPS system is complete in 1994, 8 satellites will be observable continuously from anywhere in the world and the same level of uncertainty will be obtained using a shorter averaging

  19. Multi-PLL with two-stage fusion to mitigate ionospheric scintillation effects on GPS receivers

    NASA Astrophysics Data System (ADS)

    Xu, Rui; Liu, Zhizhao; Chen, Wu

    2015-07-01

    Ionospheric scintillation poses a great threat to the reliability and accuracy of Global Positioning System (GPS) in various applications. It can increase tracking errors of the phase-locked loop (PLL) in a GPS receiver and even cause the PLL loss of lock under severe scintillations. To mitigate the effect of scintillation on GPS receivers, especially to reduce the occurrence of loss of lock, a multi-PLL with two-stage fusion (i.e., tracking fusion and output fusion) is proposed in this paper. This algorithm integrates several parallel sub-PLLs with different loop parameters into one channel to track one GPS satellite's signal. Every sub-PLL has its own discriminator, loop filter, carrier numerical controlled oscillator, and a tracking fusion (i.e., the first stage fusion). The tracking fusion of each sub-PLL integrates the Doppler frequency measurements from all other sub-PLLs to detect the state of its own sub-PLL and feeds back reliable Doppler frequency measurements. Simultaneously, the tracking fusion outputs the Doppler frequency measurements to the second stage fusion (i.e., output fusion), which integrates the outputs from all tracking fusions to provide continuous and accurate Doppler frequency measurements for the following positioning/navigation estimator. Performances of the proposed algorithm are tested using real-world GPS data with different levels of scintillations and compared with results from single-PLLs. For three real-world scintillation cases (S4 = 0.26-1.1, σϕ = 0.05-1.49 rad, and average C/N0 = 41.2-45.7 dB Hz), the multi-PLL algorithm performs more robustly than the single-PLLs and is able to keep tracking in all scintillation cases.

  20. Urban heat island influence on refraction index fluctuations from the data of spatially separated GPS-GLONASS receivers

    NASA Astrophysics Data System (ADS)

    Khutorov, Vladislav; Khutorova, Olga; Teptin, German

    2015-11-01

    In this paper we show results of troposphere fluctuation analysis and its influence on GPS phase observations. The main object of investigation is a time and spatial correlations between GPS observables induced by the atmospheric mesoscale process in troposphere. We can estimate space structure of atmospheric parameters, using the data from network based on Global Navigation Satellite System receivers. We used mathematical means of turbulence theory and wavelet analysis. The results show a significant effect on GPS signals caused by the mesoscale troposphere process and urban conditions.

  1. Gravity field error analysis: Applications of GPS receivers and gradiometers on low orbiting platforms

    NASA Technical Reports Server (NTRS)

    Schrama, E.

    1990-01-01

    The concept of a Global Positioning System (GPS) receiver as a tracking facility and a gradiometer as a separate instrument on a low orbiting platform offers a unique tool to map the Earth's gravitational field with unprecedented accuracies. The former technique allows determination of the spacecraft's ephemeris at any epoch to within 3 to 10 cm, the latter permits the measurement of the tensor of second order derivatives of the gravity field to within 0.01 to 0.0001 Eotvos units depending on the type of gradiometer. First, a variety of error sources in gradiometry where emphasis is placed on the rotational problem pursuing as well a static as a dynamic approach is described. Next, an analytical technique is described and applied for an error analysis of gravity field parameters from gradiometer and GPS observation types. Results are discussed for various configurations proposed on Topex/Poseidon, Gravity Probe-B, and Aristoteles, indicating that GPS only solutions may be computed up to degree and order 35, 55, and 85 respectively, whereas a combined GPS/gradiometer experiment on Aristoteles may result in an acceptable solution up to degree and order 240.

  2. GPS-based satellite tracking system for precise positioning

    NASA Technical Reports Server (NTRS)

    Yunck, T. P.; Melbourne, W. G.; Thornton, C. L.

    1985-01-01

    NASA is developing a Global Positioning System (GPS) based measurement system to provide precise determination of earth satellite orbits, geodetic baselines, ionospheric electron content, and clock offsets between worldwide tracking sites. The system will employ variations on the differential GPS observing technique and will use a network of nine fixed ground terminals. Satellite applications will require either a GPS flight receiver or an on-board GPS beacon. Operation of the system for all but satellite tracking will begin by 1988. The first major satellite application will be a demonstration of decimeter accuracy in determining the altitude of TOPEX in the early 1990's. By then the system is expected to yield long-baseline accuracies of a few centimeters and instantaneous time synchronization to 1 ns.

  3. Real-time GPS seismology with a stand-alone receiver: A preliminary feasibility demonstration

    NASA Astrophysics Data System (ADS)

    Colosimo, G.; Crespi, M.; Mazzoni, A.

    2011-11-01

    We show the feasibility of a real-time estimation of waveforms and coseismic displacements, within a few centimeters in accuracy, with a stand-alone dual-frequency Global Positioning System (GPS) receiver using a so-called "variometric" approach. The approach is based on time single-differences of carrier phase observations collected at a high-rate (1 Hz or more) using a stand-alone receiver, and on standard GPS broadcast products (orbits and clocks), which are ancillary information routinely available in real time. In the approach, first, the time series of epoch-by-epoch displacements are estimated. Then, provided that the collected observations are continuous, they can be summed over the interval (limited to a few minutes) over which an earthquake occurs. Since epoch-by-epoch displacements divided by the interval between consecutive epochs are essentially equal to the epoch-by-epoch velocities, this is equivalent to saying that we are using the GPS receiver as a velocimeter. Estimation biases, due to the possible mismodeling of various intervening effects (such as multipath, residual clock errors, orbit errors, and atmospheric errors), accumulate over time and display their signature as a trend in coseismic displacements. The trend can be considered linear and easily removed, at least for short intervals. Since the proposed approach (named VADASE (Variometric Approach for Displacements Analysis Stand-alone Engine)) does not require either additional technological complexity or a centralized data analysis, in principle it can be embedded into GPS receiver firmware, thereby providing a significant contribution to tsunami warning and other hazard assessment systems. After a preliminary test using a simulated example, the effectiveness of this approach was proven using real data. We analyzed the 1 Hz GPS data recorded by the International Global Navigation Satellite Systems Service station BREW during the Denali Fault, Alaska, earthquake (Mw 7.9, 3 November, 2002

  4. Precise orbit determination for the shuttle radar topography mission using a new generation of GPS receiver

    NASA Technical Reports Server (NTRS)

    Bertiger, W.; Bar-Sever, Y.; Desai, S.; Duncan, C.; Haines, B.; Kuang, D.; Lough, M.; Reichert, A.; Romans, L.; Srinivasan, J.; Webb, F.; Young, L.; Zumberge, J.

    2000-01-01

    The BlackJack family of GPS receivers has been developed at JPL to satisfy NASA's requirements for high-accuracy, dual-frequency, Y-codeless GPS receivers for NASA's Earth science missions. In this paper we will present the challenges that were overcome to meet this accuracy requirement. We will discuss the various reduced dynamic strategies, Space Shuttle dynamic models, and our tests for accuracy that included a military Y-code dual-frequency receiver (MAGR).

  5. Phase center modeling for LEO GPS receiver antennas and its impact on precise orbit determination

    NASA Astrophysics Data System (ADS)

    Jäggi, Adrian; Dach, R.; Montenbruck, O.; Hugentobler, U.; Bock, H.; Beutler, G.

    2009-12-01

    Most satellites in a low-Earth orbit (LEO) with demanding requirements on precise orbit determination (POD) are equipped with on-board receivers to collect the observations from Global Navigation Satellite systems (GNSS), such as the Global Positioning System (GPS). Limiting factors for LEO POD are nowadays mainly encountered with the modeling of the carrier phase observations, where a precise knowledge of the phase center location of the GNSS antennas is a prerequisite for high-precision orbit analyses. Since 5 November 2006 (GPS week 1400), absolute instead of relative values for the phase center location of GNSS receiver and transmitter antennas are adopted in the processing standards of the International GNSS Service (IGS). The absolute phase center modeling is based on robot calibrations for a number of terrestrial receiver antennas, whereas compatible antenna models were subsequently derived for the remaining terrestrial receiver antennas by conversion (from relative corrections), and for the GNSS transmitter antennas by estimation. However, consistent receiver antenna models for space missions such as GRACE and TerraSAR-X, which are equipped with non-geodetic receiver antennas, are only available since a short time from robot calibrations. We use GPS data of the aforementioned LEOs of the year 2007 together with the absolute antenna modeling to assess the presently achieved accuracy from state-of-the-art reduced-dynamic LEO POD strategies for absolute and relative navigation. Near-field multipath and cross-talk with active GPS occultation antennas turn out to be important and significant sources for systematic carrier phase measurement errors that are encountered in the actual spacecraft environments. We assess different methodologies for the in-flight determination of empirical phase pattern corrections for LEO receiver antennas and discuss their impact on POD. By means of independent K-band measurements, we show that zero-difference GRACE orbits can be

  6. Modeling and estimation of C1-P1 bias in GPS receivers

    NASA Astrophysics Data System (ADS)

    Gao, Y.; Lahaye, F.; Héroux, P.; Liao, X.; Beck, N.; Olynik, M.

    2001-01-01

    Modern dual-frequency global positioning system (GPS) receivers are capable of providing direct measurements of both L1 C/A (C1) and P code (P1) without the use of the Y-codes under Anti-Spoofing. A discrepancy or bias between the C1 and P1 measurements from these receivers has however been of concern to operators and users of GPS reference networks. For the purpose of modeling and estimation, the nature and characteristics of the discrepancy must be investigated. The research results presented indicate that the discrepancy between the C1 and P1 measurements contains two different types of components: one is of constant type while another is time variant. A method has been developed for their modeling and estimation. The residual C1-P1 time series after a satellite-dependent bias removal agree at a few-centimeter level, indicating the effectiveness of the proposed model. This allows the C1-P1 discrepancy, both constant and non-constant components, to be removed from GPS reference network solutions. Numerical results are provided to support the analysis.

  7. Orbiting GPS Receiver Modified to Track New L2C Signal

    NASA Technical Reports Server (NTRS)

    Meehan, Tom K.; Robison, David; Munson, Tim N.; Young, Larry E.; Stoyanov, Stephen

    2006-01-01

    The L2C signal is a great step forward for civil applications of GPS, enabling high-accuracy dual-frequency measurements. Engineers from the Jet Propulsion Laboratory and ITT teamed to reprogram FPGA firmware and add tracking software on an orbiting receiver to track the new GPS L2C signal from SAC-C. SAC-C is an Argentinean science satellite and was launched in November 2000 with a BlackJack GPS receiver. This is a dual-frequency digital receiver with 48 tracking channels and four antennas. On SAC-C, it provides precise orbits, atmospheric occultation data, tests of GPS surface reflections, and serves as an orbiting test bed for new GPS development such as the L2C tracking reported here.

  8. An observation campaign of precipitable water vapor with multiple GPS receivers in western Java, Indonesia

    NASA Astrophysics Data System (ADS)

    Realini, Eugenio; Sato, Kazutoshi; Tsuda, Toshitaka; Susilo; Manik, Timbul

    2014-12-01

    A campaign was conducted from 23 July to 5 August 2010 to measure atmospheric precipitable water vapor (PWV) using five Global Positioning System (GPS) receivers, stationed at four different locations in Jakarta and Bogor, western Java, Indonesia. Radiosondes were launched at an interval of 6 h to validate the GPS-derived PWV data. The validation resulted in a root mean square error of 2 to 3 mm in PWV. The influence of atmospheric pressure and temperature on GPS-derived PWV was evaluated. A regular semi-diurnal pressure oscillation was observed, showing an amplitude ranging from 3 to 5 hPa, which corresponds to 1.1 to 1.8 mm in PWV. A nocturnal temperature inversion layer was observed in the radiosonde profiles, which resulted in an error of about 0.5 mm in PWV. From 26 to 29 July, there was a passage of distributed rain clouds over western Java, moving southwestward from the equator toward the Indian Ocean. A second precipitation event, with scattered rain clouds forming locally near Bogor, occurred on 2 August. Both events were observed also by a C-band Doppler Radar operated near Jakarta. The highest peak of GPS-derived PWV (about 67 mm) registered during the campaign occurred on 27 July, coinciding with the distributed rainfall event. Spatial variations in the estimated PWV between the four sites were enhanced before both the analyzed rainfall events, on 27 July and 2 August. Peaks in the temporal variability of PWV were also observed in conjunction with the two events. The results indicated a relation between the space-time inhomogeneity of GPS-PWV and rainfall events in the tropics.

  9. Learning Geospatial Analysis Skills with Consumer-Grade GPS Receivers and Low Cost Spatial Analysis Software

    ERIC Educational Resources Information Center

    Linehan, Peter E.

    2006-01-01

    Spatial analysis technologies are increasingly important tools for all aspects of forest resource management. Field work previously accomplished with map, compass, and engineers' scale is now being augmented, or superseded, by the use of GPS and GIS. Professional-grade GPS receivers and commercial GIS software are preferred for their accuracy and…

  10. A GPS System-of-Systems for Science

    NASA Astrophysics Data System (ADS)

    Sherwood, R.; Mannucci, A.; Zuffada, C.; Heeg, C.

    2006-12-01

    The 2006 National Research Council (NRC) Decadal Report will stress that future directions for Earth science at NASA/NOAA will focus on achievement of a national strategy for the Earth Sciences that balances international economic competitiveness, protection of life and property, and stewardship of the planet for this and future generations. Because of the urgent need for climate measurements identified in the report, a small group from JPL was formed to explore the science benefits of maintaining GPS receivers in orbit for climate science. This is a particularly timely topic since 7 new GPS-science capable satellites were launched in 2006 (COSMIC 1-6, MetOp1), resulting in 10 GPS-science capable satellites in orbit (including CHAMP, SAC-C, GRACE). For this GPS System-of-Systems, we studied climate observations, ionosphere observations, and ocean science. For climate observations, we simulated a constellation of ten satellites in a configuration similar to COSMIC, and performed a multi-year analysis of how such a constellation would be able to characterize long-term trends in temperature. We find that such a constellation is adequate to compute zonally-averaged, monthly mean temperatures with a precision adequate to address expected climate trends of order ~0.1 K per decade. Such a constellation also has adequate local time coverage to avoid aliasing diurnal cycle trends with global climate trends. The high accuracy and consistency of GPS-based atmospheric retrievals suggests that continuously maintaining an operating constellation of such receivers is an important global observation asset for characterizing long-term climate trends. We also performed a series of simulations to determine the science returns that could be achieved with varying sizes of GPS receiver constellations. This study can be used to consider the advantages of including GPS science receivers on future satellites as dedicated constellations or constellations of opportunity. For ocean science

  11. Link calibration against receiver calibration: an assessment of GPS time transfer uncertainties

    NASA Astrophysics Data System (ADS)

    Rovera, G. D.; Torre, J.-M.; Sherwood, R.; Abgrall, M.; Courde, C.; Laas-Bourez, M.; Uhrich, P.

    2014-10-01

    We present a direct comparison between two different techniques for the relative calibration of time transfer between remote time scales when using the signals transmitted by the Global Positioning System (GPS). Relative calibration estimates the delay of equipment or the delay of a time transfer link with respect to reference equipment. It is based on the circulation of some travelling GPS equipment between the stations in the network, against which the local equipment is measured. Two techniques can be considered: first a station calibration by the computation of the hardware delays of the local GPS equipment; second the computation of a global hardware delay offset for the time transfer between the reference points of two remote time scales. This last technique is called a ‘link’ calibration, with respect to the other one, which is a ‘receiver’ calibration. The two techniques require different measurements on site, which change the uncertainty budgets, and we discuss this and related issues. We report on one calibration campaign organized during Autumn 2013 between Observatoire de Paris (OP), Paris, France, Observatoire de la Côte d'Azur (OCA), Calern, France, and NERC Space Geodesy Facility (SGF), Herstmonceux, United Kingdom. The travelling equipment comprised two GPS receivers of different types, along with the required signal generator and distribution amplifier, and one time interval counter. We show the different ways to compute uncertainty budgets, leading to improvement factors of 1.2 to 1.5 on the hardware delay uncertainties when comparing the relative link calibration to the relative receiver calibration.

  12. Swarm GPS Receiver Performance under the Influence of Ionospheric Scintillation

    NASA Astrophysics Data System (ADS)

    Ren, Le; Schön, Steffen

    2016-04-01

    The Swarm mission launched on 22 November 2013 is ESA's first constellation of satellites to study the dynamics of the Earth's magnetic field and its interaction with the Earth system. This mission consists of three identical satellites in near-polar orbits , two flying almost side-by-side at an initial altitude of 460 km, the third flying in a higher orbit of about 530 km. Each satellite is equipped with a high precision 8-channels dual-frequency receiver for the precise orbit determination, which is also the essential fundament in order to take full advantage of the data information provided by this constellation, e.g. for the recovery of gravity field. The quality of the final orbit determination depends on the observation data from the receivers. In this contribution, we will analyze the performance of the Swarm on-board receivers, especially under the influence of ionospheric scintillation caused by ionospheric irregularities. This is a prerequisite for high quality satellite positioning as well as a sound study of the ionosphere. Ionospheric scintillation can lead to the phase disturbances, cycle slips or even loss of signal tracking. The RINEX observation data from Swarm Level 1b products are used to analyze the Swarm receiver performance. We will demonstrate the signal strength, code and phase noise, different linear combinations (geometry free, ionosphere free), as well as GDOP values for the 3 Swarm satellites. The first results show that the observation data are severely disturbed and the signals could be lost around the geomagnetic equator and geomagnetic poles where the ionosphere is active. The results also show that the receivers are more stable in those areas after the update in October 2015.

  13. Improving the Quality of Low-Cost GPS Receiver Data for Monitoring Using Spatial Correlations

    NASA Astrophysics Data System (ADS)

    Zhang, Li; Schwieger, Volker

    2016-06-01

    The investigations on low-cost single frequency GPS receivers at the Institute of Engineering Geodesy (IIGS) show that u-blox LEA-6T GPS receivers combined with Trimble Bullet III GPS antennas containing self-constructed L1-optimized choke rings can already obtain an accuracy in the range of millimeters which meets the requirements of geodetic precise monitoring applications (see [27]). However, the quality (accuracy and reliability) of low-cost GPS receiver data, particularly in shadowing environment, should still be improved, since the multipath effects are the major error for the short baselines. For this purpose, several adjoined stations with low-cost GPS receivers and antennas were set up next to the metal wall on the roof of the IIGS building and measured statically for several days. The time series of three-dimensional coordinates of the GPS receivers were analyzed. Spatial correlations between the adjoined stations, possibly caused by multipath effect, will be taken into account. The coordinates of one station can be corrected using the spatial correlations of the adjoined stations, so that the quality of the GPS measurements is improved. The developed algorithms are based on the coordinates and the results will be delivered in near-real-time (in about 30 minutes), so that they are suitable for structural health monitoring applications.

  14. Error and Performance Analysis of MEMS-based Inertial Sensors with a Low-cost GPS Receiver

    PubMed Central

    Park, Minha; Gao, Yang

    2008-01-01

    Global Navigation Satellite Systems (GNSS), such as the Global Positioning System (GPS), have been widely utilized and their applications are becoming popular, not only in military or commercial applications, but also for everyday life. Although GPS measurements are the essential information for currently developed land vehicle navigation systems (LVNS), GPS signals are often unavailable or unreliable due to signal blockages under certain environments such as urban canyons. This situation must be compensated in order to provide continuous navigation solutions. To overcome the problems of unavailability and unreliability using GPS and to be cost and size effective as well, Micro Electro Mechanical Systems (MEMS) based inertial sensor technology has been pushing for the development of low-cost integrated navigation systems for land vehicle navigation and guidance applications. This paper will analyze the characterization of MEMS based inertial sensors and the performance of an integrated system prototype of MEMS based inertial sensors, a low-cost GPS receiver and a digital compass. The influence of the stochastic variation of sensors will be assessed and modeled by two different methods, namely Gauss-Markov (GM) and AutoRegressive (AR) models, with GPS signal blockage of different lengths. Numerical results from kinematic testing have been used to assess the performance of different modeling schemes.

  15. Seismo-traveling ionospheric disturbances of earthquake and tsunami waves observed by space- and ground-based GPS receivers

    NASA Astrophysics Data System (ADS)

    Liu, J. Y. G.; Chen, C. Y.; Lin, C. H.

    2015-12-01

    FORMOSAT-3/COSMIC (F3/C) is a constellation of six microsatellites launched on April 15, 2006 and has been orbiting with 72° inclination at 700 to 800 km above the earth since December 2007. The main payload of the F3/C is the GPS Occultation eXperiment (GOX) which carries out probing the radio occultation (RO) total electron content between GPS satellite and F3/C. Therefore, F3/C provides us an excellent opportunity to vertically scan ionospheric electron density from 100 up to 800 km altitude. On the other hand, worldwide ground-based GPS receivers can be employed to observe traveling ionospheric disturbances of the TEC. Here, we present the ionosphere response to seismic and tsunami waves by means of F3/C RO TEC and worldwide ground-based GPS TEC as well as existing data of infrasondes, magnetometers, and Doppler sounding systems during the 11 March 2011 M9.0 Tohoku earthquake.

  16. Performance assessment of GPS receivers during the September 24, 2011 solar radio burst event

    NASA Astrophysics Data System (ADS)

    Muhammad, Bilal; Alberti, Valentina; Marassi, Alessandro; Cianca, Ernestina; Messerotti, Mauro

    2015-10-01

    The sudden outburst of in-band solar radio noise from the Sun is recognized as one of the potential Radio Frequency Interference (RFI) sources that directly impact the performance of Global Navigation Satellite System (GNSS) receivers. On September 24, 2011, the solar active region 1302 unleashed a moderate M7.1 soft X-ray flare associated with a very powerful radio burst at 1415 MHz. The Solar Radio Burst (SRB) event spanned over three distinct episodes of solar radio noise emission that reached the maximum radio flux density of 114,144 Solar Flux Units (SFU) at 13:04:46 UTC. This paper analyzes the impact of September 24, 2011 SRB event on the performance of a significant subset of NAVSTAR Global Positioning System (GPS) receivers located in the sunlit hemisphere. The performance assessment is carried out in terms of Carrier-to-Noise power spectral density ratio (C/N0) degradation, dual-frequency pseudorange measurements availability, pseudorange residual errors, and dual-frequency positioning errors in the horizontal and vertical dimensions. We observed that during the SRB event the GPS C/N0 is reduced at most by 13 dB on L1 and 24 dB on L2. The C/N0 degradation caused the loss of lock on GPS L1 and L2 signals and significant code-tracking errors. We noticed that many stations experienced less than four satellite measurements, which are the minimum required number of measurements for position estimation. The deteriorated satellite-receiver geometry due to loss of signal lock and significant code-tracking errors during the solar radio burst event introduced large positioning errors in both the horizontal and vertical dimensions. Rise in vertical positioning error of 303 m and rise in horizontal positioning of 55 m could be noticed during the solar radio burst event.

  17. GPS

    NASA Technical Reports Server (NTRS)

    Webb, Frank H.

    2006-01-01

    Geodetic networks support the TRF requirements of NASA ESE missions. Each of SLR, VLBI, GPS substantially and uniquely contributes to TRF determination. NASA's SLR, VLBI, and GPS groups collaborate toward wide-ranging improvements in the next 5 years. NASA leverages considerable resources through its significant activity in international services. NASA faces certain challenges in continuing and advancing these activities. The Terrestrial Reference Frame (TRF) is an accurate, stable set of positions and velocities. The TRF provides the stable coordinate system that allows us to link measurements over space and time. The geodetic networks provide data for determination of the TRF as well as direct science observations.

  18. Real-time Scintillation Monitoring in Alaska from a Longitudinal Chain of ASTRA's SM-211 GPS TEC and Scintillation Receivers

    NASA Astrophysics Data System (ADS)

    Crowley, G.; Azeem, S. I.; Reynolds, A.; Santana, J.; Hampton, D. L.

    2013-12-01

    Amplitude and phase scintillation can cause serious difficulties for GPS receivers. Intense scintillation can cause loss of lock. High latitude studies generally show that phase scintillation can be severe, but the amplitude scintillation tends to be small. The reason for this is not yet understood. Furthermore, the actual causes of the ionospheric irregularities that produce high latitude scintillation are not well understood. While the gradient drift instability is thought to be important in the F-region, there may be other structures present in either the E- or F-regions. The role of particle precipitation is also not well understood. Four of ASTRA's CASES GPS receivers were deployed in Alaska to demonstrate our ability to map scintillation in realtime, to provide space weather services to GPS users, and to initiate a detailed investigation of these effects. These dual-frequency GPS receivers measure total electron content (TEC) and scintillation. The scintillation monitors were deployed in a longitudinal chain at sites in Kaktovic, Fort Yukon, Poker Flat, and Gakona. Scintillation statistics show phase scintillations to be largest at Kaktovic and smallest at Gakona. We present GPS phase scintillation and auroral emission results from the Alaska chain to characterize the correspondence between scintillation and auroral features, and to investigate the role of high latitude auroral features in driving the phase scintillations. We will also present data showing how phase scintillation can cause other GPS receivers to lose lock. The data and results are particularly valuable because they illustrate some of the challenges of using GPS systems for positioning and navigation in an auroral region like Alaska. These challenges for snowplough drivers were recently highlighted, along with the CASES SM-211 space weather monitor, in a special video in which ASTRA and three other small businesses were presented with an entrepreneurial award from William Shatner (http://youtu.be/bIVKEQH_YPk).

  19. Real-time GPS seismology with a stand-alone receiver: a preliminary feasibility demonstration

    NASA Astrophysics Data System (ADS)

    Colosimo, G.; Crespi, M.; Mazzoni, A.

    2010-12-01

    We show the feasibility of waveforms and coseismic displacements real-time estimation at few centimeters accuracy level by a stand-alone dual-frequency GPS receiver through a variometric approach. This approach is based on the time single-differences of the carrier phase observations collected at high-rate (1Hz or more) by a stand-alone receiver and on the standard GPS broadcast products (orbits, clocks). Time series of epoch-by-epoch displacements are estimated at first; then, they can be summed over the interval (limited to few minutes) when the earthquake occurs, provided the collected observations are continuous. The estimation biases due to mismodeling accumulate over time and display as a trend, which can be considered linear and easily removed thanks to the shortness of the interval. Since the proposed approach does not require any additional technological complexity nor centralized data analysis, in principle it can be embedded into the receiver firmware, providing also a significant contribution to tsunami warning systems. After a preliminary test regarding a simulated example, the effectiveness has been proven over real data. In details, we have analyzed the 1Hz GPS data recorded by the IGS station BREW during the Denali Fault, Alaska earthquake (Mw 7.9, November 3, 2002, 22:12:41 UTC) and the 5 Hz data collected by some stations included into the UNAVCO-Plate Boundary Observatory network and California Real Time Network (CRTN) during the Baja California, Mexico earthquake (Mw 7.2, April 04, 2010, 22:40:42 UTC). The comparisons with results obtained with different strategies show an agreement within few centimeters; examples for Baja California earthquake (waveforms for stations P496 e P744, to be compared with http://www.unavco.org/research_science/science_highlights/2010/M7.2-Baja.html) are shown in Figures 1 and 2. Fig. 1 - P496 Fig. 2 - P744

  20. Flight Performance Evaluation of Three GPS Receivers for Sounding Rocket Tracking

    NASA Technical Reports Server (NTRS)

    Bull, Barton; Diehl, James; Montenbruck, Oliver; Markgraf, Markus; Bauer, Frank (Technical Monitor)

    2002-01-01

    In preparation for the European Space Agency Maxus-4 mission, a sounding rocket test flight was carried out at Esrange, near Kiruna, Sweden on February 19, 2001 to validate existing ground facilities and range safety installations. Due to the absence of a dedicated scientific payload, the flight offered the opportunity to test multiple GPS receivers and assess their performance for the tracking of sounding rockets. The receivers included an Ashtech G12 HDMA receiver, a BAE (Canadian Marconi) Allstar receiver and a Mitel Orion receiver. All of them provide C/A code tracking on the L1 frequency to determine the user position and make use of Doppler measurements to derive the instantaneous velocity. Among the receivers, the G12 has been optimized for use under highly dynamic conditions and has earlier been flown successfully on NASA sounding rockets. The Allstar is representative of common single frequency receivers for terrestrial applications and received no particular modification, except for the disabling of the common altitude and velocity constraints that would otherwise inhibit its use for space application. The Orion receiver, finally, employs the same Mitel chipset as the Allstar, but has received various firmware modifications by DLR to safeguard it against signal losses and improve its tracking performance. While the two NASA receivers were driven by a common wrap-around antenna, the DLR experiment made use of a switchable antenna system comprising a helical antenna in the tip of the rocket and two blade antennas attached to the body of the vehicle. During the boost a peak acceleration of roughly l7g's was achieved which resulted in a velocity of about 1100 m/s at the end of the burn. At apogee, the rocket reached an altitude of over 80 km. A detailed analysis of the attained flight data is given together with a evaluation of different receiver designs and antenna concepts.

  1. Range filtering for sequential GPS receivers with external sensor augmentation

    NASA Technical Reports Server (NTRS)

    Paielli, Russell

    1987-01-01

    The filtering of the satellite range and range-rate measurements from single channel sequential Global Positioning System receivers is usually done with an extended Kalman filter which has state variables defined in terms of an orthogonal navigation reference frame. An attractive suboptimal alternative is range-domain filtering, in which the individual satellite measurements are filtered separately before they are combined for the navigation solution. The main advantages of range-domain filtering are decreased processing and storage requirements and simplified tuning. Several range filter mechanization alternatives are presented, along with an innovative approach for combining the filtered range-domain quantities to determine the navigation state estimate. In addition, a method is outlined for incorporating measurements from auxiliary sensors such as altimeters into the navigation state estimation scheme similarly to the satellite measurements. A method is also described for incorporating inertial measurements into the navigation state estimator as a process driver.

  2. High-resolution total electron content observations of severe ionospheric disturbances using dense GPS receiver networks

    NASA Astrophysics Data System (ADS)

    Tsugawa, Takuya; Kato, Hisao; Kubota, Minoru; Hidekatsu, Jin; Maruyama, Takashi; Nagatsuma, Tsutomu; Saito, Akinori; Nishioka, Michi; Otsuka, Yuichi; Miyake, Wataru; Supnithi, Pornchai; Kenpankho, Prasert

    Two-dimensional total electron content (TEC) maps have been derived from ground-based GPS receiver networks and applied to studies of various ionospheric disturbances since mid-1990s. For the purpose of monitoring and researching ionospheric disturbances which can degrade GNSS navigations and cause loss-of-lock on GNSS signals, National Institute of Information and Communications Technology (NICT), Japan has developed TEC maps over Japan using the dense GPS network, GEONET, which consists of more than 1,200 GPS receivers and is operated by Geophysical Survey Institute, Japan. Currently, we are providing two-dimensional maps of absolute TEC, detrended TEC with 60, 30, 15-minute window, rate of TEC change index (ROTI), and loss-of-lock on GPS signal over Japan. These data and quick-look maps since 1997 are archived and available in the website of NICT (http://wdc.nict.go.jp/IONO/). Recently developed GPS receiver networks in North America and Europe make it possible to obtain regional TEC maps with higher spatial and temporal resolution than the global weighted mean TEC maps in the IONEX format provided by several institutes such as International GNSS Service (IGS) and another global TEC map provided by MIT Haystack observatory. Recently, we have also developed the regional TEC maps over North America and Europe. These data and quick-look maps are also available in the NICT website. In this presentation, we will show some severe ionospheric events such as high latitude storm-time plasma bubbles and storm enhanced density events observed over Japan using the GPS-TEC database. These events cause loss-of-lock of GPS signals and large GPS positioning errors. We will also introduce some interesting ionospheric events over Europe and North America, and discuss about a future direction of our GPS-TEC data service.

  3. Navigator GPS Receiver for Fast Acquisition and Weak Signal Space Applications

    NASA Technical Reports Server (NTRS)

    Winternitz, Luke; Moreau, Michael; Boegner, Gregory J.; Sirotzky, Steve

    2004-01-01

    NASA Goddard Space Flight Center (GSFC) is developing a new space-borne GPS receiver that can operate effectively in the full range of Earth orbiting missions from Low Earth Orbit (LEO) to geostationary and beyond. Navigator is designed to be a fully space flight qualified GPS receiver optimized for fast signal acquisition and weak signal tracking. The fast acquisition capabilities provide exceptional time to first fix performance (TIFF) with no a priori receiver state or GPS almanac information, even in the presence of high Doppler shifts present in LEO (or near perigee in highly eccentric orbits). The fast acquisition capability also makes it feasible to implement extended correlation intervals and therefore significantly reduce Navigator s acquisition threshold. This greatly improves GPS observability when the receiver is above the GPS constellation (and satellites must be tracked from the opposite side of the Earth) by providing at least 10 dB of increased acquisition sensitivity. Fast acquisition and weak signal tracking algorithms have been implemented and validated on a hardware development board. A fully functional version of the receiver, employing most of the flight parts, with integrated navigation software is expected by mid 2005. An ultimate goal of this project is to license the Navigator design to an industry partner who will then market the receiver as a commercial product.

  4. Pre-Launch Testing of GPS Receivers for Geodetic Space Missions

    NASA Technical Reports Server (NTRS)

    Davis, George; Davis, Edward; Luthcke, Scott; Hawkins, Kimberly; Bauer, Frank (Technical Monitor)

    2000-01-01

    The methodology used and the results obtained in the pre-flight testing of the Blackjack Global Positioning System (GPS) space receiver for the Vegetation Canopy Lidar Mission (VCL) and the Ice, Cloud, and Land Elevation Satellite (ICESat) spacecraft is described. Both real and simulated signals were used to: (1) assess the accuracy and coverage of the navigation solutions, (2) assess the accuracy and stability of the 1-PPS timing signal, (3) assess the precision of the carrier phase observable, and (4) measure the cold-start time to first fix. In addition, an anechoic chamber was used to measure the antenna phase centers with millimeter-level precision. While the test results have generally been excellent and are discussed in this paper, emphasis is placed on describing the test methodology. It is anticipated that future geodetic satellite missions using GPS for navigation, timing, and precise orbit determination (POD) can employ the same tests for pre-launch performance assessment of their particular receiver.

  5. Preliminary Analysis of the CASES GPS Receiver Performance during Simulated Seismic Displacements

    NASA Astrophysics Data System (ADS)

    De la Rosa-Perkins, A.; Reynolds, A.; Crowley, G.; Azeem, I.

    2014-12-01

    We explore the ability of a new GPS software receiver, called CASES (Connected Autonomous Space Environment Sensor), to measure seismic displacements in realtime. Improvements in GPS technology over the last 20 years allow for precise measurement of ground motion during seismic events. For example, GPS data has been used to calculate displacement histories at an earthquake's epicenter and fault slip estimations with great accuracy. This is supported by the ability to measure displacements directly using GPS, bypassing the double integration that accelerometers require, and by higher clipping limits than seismometers. The CASES receiver developed by ASTRA in collaboration with Cornell University and the University of Texas, Austin represents a new geodetic-quality software-based GPS receiver that measures ionospheric space weather in addition to the usual navigation solution. To demonstrate, in a controlled environment, the ability of the CASES receiver to measure seismic displacements, we simulated ground motions similar to those generated during earthquakes, using a shake box instrumented with an accelerometer and a GPS antenna. The accelerometer measured the box's actual displacement. The box moved on a manually controlled axis that underwent varied one-dimensional motions (from mm to cm) at different frequencies and amplitudes. The CASES receiver was configured to optimize the accuracy of the position solution. We quantified the CASES GPS receiver performance by comparing the GPS solutions against the accelerometer data using various statistical analysis methods. The results of these tests will be presented. The CASES receiver is designed with multiple methods of accessing the data in realtime, ranging from internet connection, blue-tooth, cell-phone modem and Iridium modem. Because the CASES receiver measures ionospheric space weather in addition to the usual navigation solution, CASES provides not only the seimic signal, but also the ionospheric space weather

  6. Line Focus Receiver Infrared Temperature Survey System

    Energy Science and Technology Software Center (ESTSC)

    2010-06-01

    For ongoing maintenance and performance purposes, solar parabolic trough field operators desire to know that the Heat Collection Elements (HCEs) are performing properly. Measuring their temperature is one way of doing this One 30MW field can contain approximately 10,000 HCE's. This software interfaces with a GPS receiver and an infrared camera. It takes global positioning data from the GPS and uses this information to automate the infrared image capture and temperature analysis of individual solarmore » parabolic HCEs in a solar parabolic trough field With this software system an entire 30MW field can be surveyed in 2-3 days.« less

  7. Line Focus Receiver Infrared Temperature Survey System

    SciTech Connect

    Wendelin, Tim

    2010-06-01

    For ongoing maintenance and performance purposes, solar parabolic trough field operators desire to know that the Heat Collection Elements (HCEs) are performing properly. Measuring their temperature is one way of doing this One 30MW field can contain approximately 10,000 HCE's. This software interfaces with a GPS receiver and an infrared camera. It takes global positioning data from the GPS and uses this information to automate the infrared image capture and temperature analysis of individual solar parabolic HCEs in a solar parabolic trough field With this software system an entire 30MW field can be surveyed in 2-3 days.

  8. Efficient detection and signal parameter estimation with applications to high dynamic GPS receivers

    NASA Technical Reports Server (NTRS)

    Kumar, R.

    1988-01-01

    A novel technique for simultaneously detecting data and estimating the parameters of a received carrier signal phase modulated by unknown data and experiencing very high Doppler, Doppler rate, etc. is discussed. Such a situation arises, for example, in the case of Global Positioning Systems (DPS) where the signal parameters are directly related to the position, velocity and acceleration of the GPS receiver. The proposed scheme is based upon first estimating the received signal local (data dependent) parameters over two consecutive bit periods, followed by the detection of a possible jump in these parameters. The presence of a detected jump signifies a data transition which is then removed from the received signal. This effectively demodulated signal is then processed to provide the estimates of global (data independent) parameters of the signal related to the position, velocity, etc. of the receiver. One of the key features of the proposed algorithm is the introduction of two different schemes which can provide an improvement of up to 3 dB over the conventional implementation of Kalman filter as applied to phase and frequency estimation, under low to medium signal-to-noise ratio conditions.

  9. An Interdisciplinary Approach at Studying the Earth-Sun System with GPS/GNSS and GPS-like Signals

    NASA Technical Reports Server (NTRS)

    Zuffada, Cinzia; Hajj, George; Mannucci, Anthony J.; Chao, Yi; Ao, Chi; Zumberge, James

    2005-01-01

    The value of Global Positioning Satellites (GPS) measurements to atmospheric science, space physics, and ocean science, is now emerging or showing a potential to play a major role in the evolving programs of NASA, NSF and NOAA. The objective of this communication is to identify and articulate the key scientific questions that are optimally, or perhaps uniquely, addressed by GPS or GPS-like observations, and discuss their relevance to existing or planned national Earth-science research programs. The GPS-based ocean reflection experiments performed to date have demonstrated the precision and spatial resolution suitable to altimetric applications that require higher spatial resolution and more frequent repeat than the current radar altimeter satellites. GPS radio occultation is promising as a climate monitoring tool because of its benchmark properties: its raw observable is based on extremely accurate timing measurements. GPS-derived temperature profiles can provide meaningful climate trend information over decadal time scales without the need for overlapping missions or mission-to-mission calibrations. By acquiring data as GPS satellites occult behind the Earth's limb, GPS also provides high vertical resolution information on the vertical structure of electron density with global coverage. New experimental techniques will create more comprehensive TEC maps by using signals reflected from the oceans and received in orbit. This communication will discuss a potential future GNSS Earth Observing System project which would deploy a constellation of satellites using GPS and GPS-like measurements, to obtain a) topography measurements based on GPS reflections with an accuracy and horizontal resolution suitable for eddy monitoring, and h) climate-records quality atmospheric temperature profiles. The constellation would also provide for measurements of ionospheric elec tron density. This is a good example of an interdisciplinary mission concept, with broad science objectives

  10. A GPS measurement system for precise satellite tracking and geodesy

    NASA Technical Reports Server (NTRS)

    Yunck, T. P.; Wu, S.-C.; Lichten, S. M.

    1985-01-01

    NASA is pursuing two key applications of differential positioning with the Global Positioning System (GPS): sub-decimeter tracking of earth satellites and few-centimeter determination of ground-fixed baselines. Key requirements of the two applications include the use of dual-frequency carrier phase data, multiple ground receivers to serve as reference points, simultaneous solution for use position and GPS orbits, and calibration of atmospheric delays using water vapor radiometers. Sub-decimeter tracking will be first demonstrated on the TOPEX oceanographic satellite to be launched in 1991. A GPS flight receiver together with at least six ground receivers will acquire delta range data from the GPS carriers for non-real-time analysis. Altitude accuracies of 5 to 10 cm are expected. For baseline measurements, efforts will be made to obtain precise differential pseudorange by resolving the cycle ambiguity in differential carrier phase. This could lead to accuracies of 2 or 3 cm over a few thousand kilometers. To achieve this, a high-performance receiver is being developed, along with improved calibration and data processing techniques. Demonstrations may begin in 1986.

  11. Standalone GPS L1 C/A Receiver for Lunar Missions

    PubMed Central

    Capuano, Vincenzo; Blunt, Paul; Botteron, Cyril; Tian, Jia; Leclère, Jérôme; Wang, Yanguang; Basile, Francesco; Farine, Pierre-André

    2016-01-01

    Global Navigation Satellite Systems (GNSSs) were originally introduced to provide positioning and timing services for terrestrial Earth users. However, space users increasingly rely on GNSS for spacecraft navigation and other science applications at several different altitudes from the Earth surface, in Low Earth Orbit (LEO), Medium Earth Orbit (MEO), Geostationary Earth Orbit (GEO), and feasibility studies have proved that GNSS signals can even be tracked at Moon altitude. Despite this, space remains a challenging operational environment, particularly on the way from the Earth to the Moon, characterized by weaker signals with wider gain variability, larger dynamic ranges resulting in higher Doppler and Doppler rates and critically low satellite signal availability. Following our previous studies, this paper describes the proof of concept “WeakHEO” receiver; a GPS L1 C/A receiver we developed in our laboratory specifically for lunar missions. The paper also assesses the performance of the receiver in two representative portions of an Earth Moon Transfer Orbit (MTO). The receiver was connected to our GNSS Spirent simulator in order to collect real-time hardware-in-the-loop observations, and then processed by the navigation module. This demonstrates the feasibility, using current technology, of effectively exploiting GNSS signals for navigation in a MTO. PMID:27005628

  12. Standalone GPS L1 C/A Receiver for Lunar Missions.

    PubMed

    Capuano, Vincenzo; Blunt, Paul; Botteron, Cyril; Tian, Jia; Leclère, Jérôme; Wang, Yanguang; Basile, Francesco; Farine, Pierre-André

    2016-01-01

    Global Navigation Satellite Systems (GNSSs) were originally introduced to provide positioning and timing services for terrestrial Earth users. However, space users increasingly rely on GNSS for spacecraft navigation and other science applications at several different altitudes from the Earth surface, in Low Earth Orbit (LEO), Medium Earth Orbit (MEO), Geostationary Earth Orbit (GEO), and feasibility studies have proved that GNSS signals can even be tracked at Moon altitude. Despite this, space remains a challenging operational environment, particularly on the way from the Earth to the Moon, characterized by weaker signals with wider gain variability, larger dynamic ranges resulting in higher Doppler and Doppler rates and critically low satellite signal availability. Following our previous studies, this paper describes the proof of concept "WeakHEO" receiver; a GPS L1 C/A receiver we developed in our laboratory specifically for lunar missions. The paper also assesses the performance of the receiver in two representative portions of an Earth Moon Transfer Orbit (MTO). The receiver was connected to our GNSS Spirent simulator in order to collect real-time hardware-in-the-loop observations, and then processed by the navigation module. This demonstrates the feasibility, using current technology, of effectively exploiting GNSS signals for navigation in a MTO. PMID:27005628

  13. From BlackJack to GOX: the transfer, test, and validation of the ROCSat-3 GPS occultation receiver

    NASA Technical Reports Server (NTRS)

    Farrington, Allen H.; Armatys, Michael; Bell, Bryan; Charles, Jeff; Lahmeyer, Chuck; Lee, Cynthia; Meehan, Tom; Munson, Tim; Robison, David; Srinivasan, Jeff; Stecheson, Ted; Young, Larry

    2004-01-01

    ROCSat-3's primary instrument is the GPS Occultation Receiver (GOX) and is based on the Jet Propulsion Laboratory's (JPL) proven BlackJack GPS Receiver. The COSMIC GOX receivers will demonstrate an important new operational data type for near-real-time assimilation into weather models by providing over 2500 atmospheric profiles per day with a global distribution.

  14. IMU/GPS System Provides Position and Attitude Data

    NASA Technical Reports Server (NTRS)

    Lin, Ching Fang

    2006-01-01

    A special navigation system is being developed to provide high-quality information on the position and attitude of a moving platform (an aircraft or spacecraft), for use in pointing and stabilization of a hyperspectral remote-sensing system carried aboard the platform. The system also serves to enable synchronization and interpretation of readouts of all onboard sensors. The heart of the system is a commercially available unit, small enough to be held in one hand, that contains an integral combination of an inertial measurement unit (IMU) of the microelectromechanical systems (MEMS) type, Global Positioning System (GPS) receivers, a differential GPS subsystem, and ancillary data-processing subsystems. The system utilizes GPS carrier-phase measurements to generate time data plus highly accurate and continuous data on the position, attitude, rotation, and acceleration of the platform. Relative to prior navigation systems based on IMU and GPS subsystems, this system is smaller, is less expensive, and performs better. Optionally, the system can easily be connected to a laptop computer for demonstration and evaluation. In addition to airborne and spaceborne remote-sensing applications, there are numerous potential terrestrial sensing, measurement, and navigation applications in diverse endeavors that include forestry, environmental monitoring, agriculture, mining, and robotics.

  15. High dynamic global positioning system receiver

    NASA Technical Reports Server (NTRS)

    Hurd, W. J. (Inventor)

    1986-01-01

    A Global Positioning System (GPS) receiver having a number of channels, receives an aggregate of pseudorange code time division modulated signals. The aggregate is converted to baseband and then to digital form for separate processing in the separate channels. A fast fourier transform processor computes the signal energy as a function of Doppler frequency for each correlation lag, and a range and frequency estimator computes estimates of pseudorange, and frequency. Raw estimates from all channels are used to estimate receiver position, velocity, clock offset and clock rate offset in a conventional navigation and control unit, and based on the unit that computes smoothed estimates for the next measurement interval.

  16. International time transfer and portable clock evaluation using GPS timing receivers: Preliminary results

    NASA Technical Reports Server (NTRS)

    Wardrip, S. C.; Buisson, J. A.; Oaks, O. J.; Lister, M. J.; Detoma, E.; Dachel, P.; Stalder, T.; Warren, H.; Winkler, G. M. R.; Luther, G.

    1985-01-01

    The overall experiment was designed to test the positioning and navigation capabilities of the GPS timing receivers developed by the Naval Research Laboratory (NRL) for the NASA Goddard Laser Tracking Network (GITN). To perform this experiment, a reliable and redundant time scale was set up onboard the ship, and a back-up on shore. This situation provided the opportunity to perform simultaneously a timing experiment ideally divided into two parts, the main objectives of the experimentation being: (1) To test GPS timing receiver synchronization capabilities on a moving platform, and to perform an intercontinental synchronization via GPS between participating international timing laboratories in Europe and in the United States. (2) To evaluate the performance of cesium portable clocks in the field.

  17. Navstar Global Positioning System (GPS) clock program: Present and future

    NASA Technical Reports Server (NTRS)

    Tennant, D. M.

    1981-01-01

    Global Positioning System (GPS) program status are discussed and plans for ensuring the long term continuation of the program are presented. Performance of GPS clocks is presented in terms of on orbit data as portrayed by GPS master control station kalman filter processing. The GPS Clock reliability program is reviewed in depth and future plans fo the overall clock program are published.

  18. Evaluation of Mobile Phone Interference With Aircraft GPS Navigation Systems

    NASA Technical Reports Server (NTRS)

    Pace, Scott; Oria, A. J.; Guckian, Paul; Nguyen, Truong X.

    2004-01-01

    This report compiles and analyzes tests that were conducted to measure cell phone spurious emissions in the Global Positioning System (GPS) radio frequency band that could affect the navigation system of an aircraft. The cell phone in question had, as reported to the FAA (Federal Aviation Administration), caused interference to several GPS receivers on-board a small single engine aircraft despite being compliant with data filed at the time with the FCC by the manufacturer. NASA (National Aeronautics and Space Administration) and industry tests show that while there is an emission in the 1575 MHz GPS band due to a specific combination of amplifier output impedance and load impedance that induces instability in the power amplifier, these spurious emissions (i.e., not the intentional transmit signal) are similar to those measured on non-intentionally transmitting devices such as, for example, laptop computers. Additional testing on a wide sample of different commercial cell phones did not result in any emission in the 1575 MHz GPS Band above the noise floor of the measurement receiver.

  19. LANL receiver system development

    SciTech Connect

    Laubscher, B.; Cooke, B.; Cafferty, M.; Olivas, N.

    1997-08-01

    The CALIOPE receiver system development at LANL is the story of two technologies. The first of these technologies consists of off-the-shelf mercury-cadmium-telluride (MCT) detectors and amplifiers. The vendor for this system is Kolmar Technologies. This system was fielded in the Tan Trailer I (TTI) in 1995 and will be referred to in this paper as GEN I. The second system consists of a MCT detector procured from Santa Barbara Research Center (SBRC) and an amplifier designed and built by LANL. This system was fielded in the Tan Trailer II (TTII) system at the NTS tests in 1996 and will be referred to as GEN II. The LANL CALIOPE experimental plan for 1996 was to improve the lidar system by progressing to a higher rep rate laser to perform many shots in a much shorter period of time. In keeping with this plan, the receiver team set a goal of developing a detector system that was background limited for the projected 100 nanosecond (ns) laser pulse. A set of detailed simulations of the DIAL lidar experiment was performed. From these runs, parameters such as optimal detector size, field of view of the receiver system, nominal laser return power, etc. were extracted. With this information, detector physics and amplifier electronic models were developed to obtain the required specifications for each of these components. These derived specs indicated that a substantial improvement over commercially available, off-the-shelf, amplifier and detector technologies would be needed to obtain the goals. To determine if the original GEN I detector was usable, the authors performed tests on a 100 micron square detector at cryogenic temperatures. The results of this test and others convinced them that an advanced detector was required. Eventually, a suitable detector was identified and a number of these single element detectors were procured from SBRC. These single element detectors were witness for the detector arrays built for another DOE project.

  20. Atomic clock augmentation for receivers using the Global Positioning System

    NASA Astrophysics Data System (ADS)

    Kline, Paul Andrew

    For receivers using the Global Positioning System (GPS), it is standard procedure to treat the receiver clock bias from GPS time as an unknown. This requires four range measurements to the satellites in order to solve for three dimensional position and clock offset. If the receiver clock could be synchronized with GPS time, the extra range measurement would not be necessary. To achieve this synchronization, a stable frequency reference must be incorporated into the GPS user set. This concept is known as clock aiding or clock augmentation of GPS receivers. Clock augmentation increases the availability of the navigation function because only three GPS satellites are required. Also, it is shown that clock augmentation improves vertical accuracy by reducing the vertical dilution of precision (VDOP), which is a unitless multiplier that translates range measurement error into vertical position error. This improvement in vertical accuracy is particularly beneficial for applications involving final approach and landing of aircraft using GPS, because GPS typically provides better horizontal accuracy than vertical accuracy. The benefits of atomic clock augmentation are limited by factors that cause a loss of synchronization either between the receiver and GPS time, or between ground station and airborne receivers processing GPS data in differential mode (DGPS). Among the error sources that cause a clock offset are antenna rotation, hardware drifts due to temperature variations, and relativistic effects for GPS receivers on moving platforms. Antenna rotation and temperature effects are addressed and supported by experimental data. It is shown that two particular relativity terms thought to be missing from GPS receiver algorithms are not evident in data collected during a flight test experiment. Upon addressing the error sources, the dissertation concludes with analysis of DGPS data collected during a flight test at the Federal Aviation Administration (FAA) Tech Center in

  1. Low-cost inertial/GPS for ballistic missiles with application to unmanned systems

    NASA Astrophysics Data System (ADS)

    Roberts, Chris E.; Jenkins, Philip N.; Osborn, Charles T.

    1996-05-01

    Many advances in inertial navigation have been made over the last decade. Small, lightweight inertial measurement units (IMU) have been developed which provide suitable accuracy at a reasonable cost for many unmanned systems. Price has also dropped to previously unheard of levels (under 10,000 dollars for large buys). IMUs can be augmented with global positioning system (GPS) receivers to provide highly accurate and robust navigation capability. GPS receivers have also dropped in size and cost and are becoming an attractive option for coupling with an inertial system. GPS systems alone are vulnerable to jamming and are not a good choice for military applications where jamming is a consideration. Current Army policy is not to use GPS as a mission essential element. The focus of this paper will be on low cost IMUs with GPS and their application to unmanned vehicles. In particular, the program to add guidance to the multiple launch rocket system extended range rocket will be discussed.

  2. GPS receiver algorithms for suppression of narrowband and structured wideband interference

    NASA Astrophysics Data System (ADS)

    Madhani, Premal Harish

    This dissertation describes algorithms that enhance the acquisition and tracking performance of a GPS receiver in the presence of narrowband and structured wideband interference. As GPS becomes an essential element of the civil infrastructure in the areas of aviation, ground transportation, communications, and power distribution, its vulnerability to interference must be addressed. Unintentional interference typically takes the form of a narrowband signal. Structured wideband interference can result from the ground-based augmentation of GPS with pseudolites. Algorithms that enhance performance for these two situations are developed and described in detail. Pseudolites are a very useful augmentation to GPS that provide enhanced coverage in areas of high blockage or for critical missions such as aircraft landing. However, pseudolites may introduce what is known as near-far interference, where a pseudolite signal interferes with the acquisition and tracking of weaker satellite signals. I have applied the technique of successive interference cancellation (SIC) to improve acquisition performance in the presence of a pseudolite signal. An extension of SIC to the identification and cancellation of pseudolite multipath is also given. The performance of these algorithms is demonstrated on simulated and experimental data, showing significant improvement over conventional techniques. The low level of GPS signals makes them susceptible to narrowband interference, despite the inherent resistance to interference afforded by GPS spread spectrum modulation. In my research I have investigated a number of algorithms that can increase the robustness of GPS receivers in a hostile narrowband electromagnetic environment. This dissertation describes several adaptive estimators which are applied to simulated GPS data. Comparisons are made in terms of post-correlation signal-to-noise ratio, tracking errors, and computational requirements. Conventional techniques of high accuracy Doppler

  3. Delay/Doppler-Mapping GPS-Reflection Remote-Sensing System

    NASA Technical Reports Server (NTRS)

    Lowe, Stephen; Kroger, Peter; Franklin, Garth; LeBrecque, John; Lerma, Jesse; Lough, Michael; Marcin, Martin; Muellerschoen, Ronald; Spitzmesser, Donovan; Young, Lawrence

    2003-01-01

    A radio receiver system that features enhanced capabilities for remote sensing by use of reflected Global Positioning System (GPS) signals has been developed. This system was designed primarily for ocean altimetry, but can also be used for scatterometry and bistatic synthetic-aperture radar imaging. Moreover, it could readily be adapted to utilize navigation-satellite systems other than the GPS, including the Russian Global Navigation Satellite System GLONASS) and the proposed European Galileo system. This remote-sensing system offers both advantages and disadvantages over traditional radar altimeters: One advantage of GPS-reflection systems is that they cost less because there is no need to transmit signals. Another advantage is that there are more simultaneous measurement opportunities - one for each GPS satellite in view. The primary disadvantage is that in comparison with radar signals, GPS signals are weaker, necessitating larger antennas and/or longer observations. This GPS-reflection remote-sensing system was tested in aircraft and made to record and process both (1) signals coming directly from GPS satellites by means of an upward-looking antenna and (2) GPS signals reflected from the ground by means of a downward-looking antenna. In addition to performing conventional GPS processing, the system records raw signals for postprocessing as required.

  4. Evaluating the velocity accuracy of an integrated GPS/INS system: Flight test results. [Global positioning system/inertial navigation systems (GPS/INS)

    SciTech Connect

    Owen, T.E.; Wardlaw, R.

    1991-01-01

    Verifying the velocity accuracy of a GPS receiver or an integrated GPS/INS system in a dynamic environment is a difficult proposition when many of the commonly used reference systems have velocity uncertainities of the same order of magnitude or greater than the GPS system. The results of flight tests aboard an aircraft in which multiple reference systems simultaneously collected data to evaluate the accuracy of an integrated GPS/INS system are reported. Emphasis is placed on obtaining high accuracy estimates of the velocity error of the integrated system in order to verify that velocity accuracy is maintained during both linear and circular trajectories. Three different reference systems operating in parallel during flight tests are used to independently determine the position and velocity of an aircraft in flight. They are a transponder/interrogator ranging system, a laser tracker, and GPS carrier phase processing. Results obtained from these reference systems are compared against each other and against an integrated real time differential based GPS/INS system to arrive at a set of conclusions about the accuracy of the integrated system.

  5. Application of a novel multi-stage signal parameter estimator to high dynamic GPS receivers

    NASA Technical Reports Server (NTRS)

    Kumar, R.

    1990-01-01

    The performance of a novel multistage estimator when applied to the estimation of the position, velocity, and acceleration of high dynamic Global Positioning System (GPS) receivers is discussed. For the present application, a two-stage specialization of the more general estimation scheme is considered, wherein the first-stage algorithm is selected to be a modified least-squares algorithm operating upon the differential signal model and referred to as differential least-squares (DLS) and the second stage is simply an extended Kalman filter (EKF). In terms of the threshold on received carrier power-to-noise power spectral density ratio (CNR), when compared to the single-stage EKF algorithm, the DLS-EKF algorithm is about 1.5-2.0 dB better in terms of threshold and outperforms the crossproduct AFC (automatic frequency control) loop by 2-5 dB. For the case when data modulation is present, the proposed scheme provides an improvement of about 6 dB in terms of CNR compared to an earlier approximate MLE (maximum likelihood estimation) scheme. There are also very significant improvements in terms of other performance measures.

  6. The Impact on the Positioning Accuracy of the Frequency Reference of a GPS Receiver

    NASA Astrophysics Data System (ADS)

    Yeh, Ta-Kang; Chen, Chieh-Hung; Xu, Guochang; Wang, Chuan-Sheng; Chen, Kwo-Hwa

    2013-01-01

    Despite the pervasive use of the global positioning system (GPS) as a positioning technology for its high efficiency and accuracy, several factors reduce its performance. This study examines to which extent the frequency offset and the frequency stability of the internal quartz oscillator or of an externally supplied rubidium oscillator have an influence. Observations were made at the Taiwan Ching Yun University (TCYU) tracking station, where a quartz oscillator and a rubidium oscillator were applied alternatively on a monthly basis throughout a 16-month period. Moreover, the accuracy of the local oscillator used in this study was calibrated by the National Standard Time and Frequency Laboratory, Taiwan. The frequency offset and frequency stability calculated via the remote method at the TCYU station were compared with values (uncertainty is 3.0E-13) measured directly at the National Standard Time and Frequency Laboratory, Taiwan. Analytical results show that the two methods vary by 1.4E-10 in terms of frequency offset and by 6.5E-12 in terms of frequency stability, demonstrating that the remote method can yield computational results almost as accurate as direct measurement. Positioning precision results also show that rubidium oscillator accuracy improved by 5, 11, and 15 % for short-, medium-, and long-baseline positioning, respectively, indicating that clock quality is more influential for long-baseline GPS relative positioning and that the frequency stability of a receiver clock is far more critical than the frequency offset. On the other hand, the positioning performance noted is essentially independent (max. 15 % change) of the reference frequency stability, which indeed differed by 4 orders of magnitude.

  7. Retrieving real-time precise co-seismic displacements with a standalone single-frequency GPS receiver

    NASA Astrophysics Data System (ADS)

    Chen, Kejie; Ge, Maorong; Li, Xingxing; Babeyko, Andrey; Ramatschi, Markus; Bradke, Markus

    2015-08-01

    Nowadays, Global Positioning System (GPS) plays an increasingly important role in retrieving real-time precise co-seismic displacements for geo-hazard monitoring and early warning. Several real-time positioning approaches have been demonstrated for such purpose, such as real-time kinematic relative positioning, precise point positioning, etc., where dual-frequency geodetic receivers are applied for the removal of ionosphere delays by inter-frequency combination. At the same time, it would be also useful to develop efficient algorithms for estimating precise displacements with low-cost GPS receivers since they can make a denser network or multi-sensors combination without putting too much financial burden. In this contribution, we present a new method to retrieve precise co-seismic displacements in real-time using a standalone single-frequency receiver. In the new method, observations prior to an earthquake are utilized to establish a precise ionospheric delay prediction model, so that precise co-seismic displacements can be obtained without any convergence process. Our method was validated with an outdoor experiment as well as by re-processing of 1-Hz GPS data collected by the GEONET network during the 2011 Tohoku Mw 9.0 earthquake. For the latter, RMS against dual-frequency receivers constituted 2 cm for horizontal components and 3 cm for the vertical component. We specially address the observation biases and their impact on the accuracy of single frequency positioning. Our approach makes real-time GPS displacement monitoring with dense network much more affordable in terms of financial costs.

  8. Dynamic Accuracy of GPS Receivers for Use in Health Research: A Novel Method to Assess GPS Accuracy in Real-World Settings.

    PubMed

    Schipperijn, Jasper; Kerr, Jacqueline; Duncan, Scott; Madsen, Thomas; Klinker, Charlotte Demant; Troelsen, Jens

    2014-01-01

    The emergence of portable global positioning system (GPS) receivers over the last 10 years has provided researchers with a means to objectively assess spatial position in free-living conditions. However, the use of GPS in free-living conditions is not without challenges and the aim of this study was to test the dynamic accuracy of a portable GPS device under real-world environmental conditions, for four modes of transport, and using three data collection intervals. We selected four routes on different bearings, passing through a variation of environmental conditions in the City of Copenhagen, Denmark, to test the dynamic accuracy of the Qstarz BT-Q1000XT GPS device. Each route consisted of a walk, bicycle, and vehicle lane in each direction. The actual width of each walking, cycling, and vehicle lane was digitized as accurately as possible using ultra-high-resolution aerial photographs as background. For each trip, we calculated the percentage that actually fell within the lane polygon, and within the 2.5, 5, and 10 m buffers respectively, as well as the mean and median error in meters. Our results showed that 49.6% of all ≈68,000 GPS points fell within 2.5 m of the expected location, 78.7% fell within 10 m and the median error was 2.9 m. The median error during walking trips was 3.9, 2.0 m for bicycle trips, 1.5 m for bus, and 0.5 m for car. The different area types showed considerable variation in the median error: 0.7 m in open areas, 2.6 m in half-open areas, and 5.2 m in urban canyons. The dynamic spatial accuracy of the tested device is not perfect, but we feel that it is within acceptable limits for larger population studies. Longer recording periods, for a larger population are likely to reduce the potentially negative effects of measurement inaccuracy. Furthermore, special care should be taken when the environment in which the study takes place could compromise the GPS signal. PMID:24653984

  9. CASES: A Novel Low-Cost Ground-based Dual-Frequency GPS Software Receiver

    NASA Astrophysics Data System (ADS)

    Haacke, B.; Crowley, G.; Reynolds, A.; Bust, G. S.; Kintner, P. M.; Psaiki, M.; Humphreys, T. E.; Powell, S.; O'Hanlon, B.

    2010-12-01

    GPS receivers can be used for monitoring space weather events such as TEC variations and scintillation. The new CASES GPS sensor developed by ASTRA, Cornell and UTAustin represents a revolutionary advance in dual frequency GPS space-weather monitoring. CASES is a paperback-novel-sized dual-frequency GPS software receiver with robust dual-frequency tracking performance, stand-alone capability, and complete software upgradability. This sensor measures and calculates TEC with a relative accuracy of a few 0.01 TECU at a cadence of up to 100 Hz. It measures amplitude and phase at up to 100 Hz on both L1 and L2, for up to 12 satellites in view. It calculates the scintillation severity indicators S4, τ0, and σφ at a cadence that is user defined. It is able to track through scintillation with {S4, τ0, amplitude} combinations as severe as {0.8, 0.8 seconds, 43 dB-Hz (nominal)} (i.e., commensurate with vigorous post-sunset equatorial scintillation) with a mean time between cycle slips greater than 240 seconds and with a mean time between frequency-unlock greater than 1 hour. Other capabilities and options include: Various data interface solutions; In-receiver and network-wide calibration of biases, and detection and mitigation of multipath; Network-wide automated remote configuration of receivers, quality control, re-processing, archiving and redistribution of data in real-time; Software products for data-processing and visualization. The low price of the sensor means that many more instruments can be purchased on a fixed budget, which will lead to new kinds of opportunities for monitoring and scientific study, including networked applications. Other uses for CASES receivers include geodetic and seismic monitoring, measurement of precipitable water vapor in the troposphere at meso-scale resolution, and educational outreach.

  10. Evaluation of a High-Sensitivity GPS Receiver for Kinematics Application in Regions with High Shading

    NASA Astrophysics Data System (ADS)

    Suhandri, H. F.; Becker, D.; Kleusberg, A.

    2009-04-01

    GPS positioning has been very much improved with high-sensitivity GPS (HSGPS) receivers. This kind of receiver can track the signal until 20-25dB below the level of conventional receivers. Obviously, no problem occurs when GPS technology is used for air and ocean vehicles navigation; sufficient and/or redundant signals can be easily acquired due to good hemispherical signal reception. A problem arises whenever signals cannot be traced anymore, if not enough satellites are available or if there is very weak signal reception in forest areas or between buildings. Those situations cannot be avoided or eliminated in land vehicle navigation. The HSGPS technology tries to solve those problems by tracking signals below the normal signal threshold of non-HSGPS receivers. This paper discusses the two factors of availability and accuracy in the context of navigation with HSGPS receivers. In order to investigate these issues some scenarios of receivers-placing will be examined which represent various receiver environments: good hemispherical signal reception, strong signal shading environment and indoor environment. The signal availability and accuracy are investigated during observation sessions of several hours by comparing the measurements of the HSGPS receiver with the measurements of a conventional, non-HSGPS receiver. As expected, the non-HSGPS receiver yields the same level of availability as the HSGPS receiver in an environment with good hemispherical signal reception. When both receivers are located in an environment with significant signal shading, the percentage of availability will significantly decay for the non-HSGPS receiver whereas the availability of the HSGPS receiver is much less reduced. However the results from the HSGPS receiver in this case are at a significantly reduced accuracy level. The accuracy level is assessed by using three parameters: i) the difference between the C/A code and the carrier phase in order to investigate how big the multipath and

  11. Software for a GPS-Reflection Remote-Sensing System

    NASA Technical Reports Server (NTRS)

    Lowe, Stephen

    2003-01-01

    A special-purpose software Global Positioning System (GPS) receiver designed for remote sensing with reflected GPS signals is described in Delay/Doppler-Mapping GPS-Reflection Remote-Sensing System (NPO-30385), which appears elsewhere in this issue of NASA Tech Briefs. The input accepted by this program comprises raw (open-loop) digitized GPS signals sampled at a rate of about 20 MHz. The program processes the data samples to perform the following functions: detection of signals; tracking of phases and delays; mapping of delay, Doppler, and delay/Doppler waveforms; dual-frequency processing; coherent integrations as short as 125 s; decoding of navigation messages; and precise time tagging of observable quantities. The software can perform these functions on all detectable satellite signals without dead time. Open-loop data collected over water, land, or ice and processed by this software can be further processed to extract geophysical information. Possible examples include mean sea height, wind speed and direction, and significant wave height (for observations over the ocean); bistatic-radar terrain images and measures of soil moisture and biomass (for observations over land); and estimates of ice age, thickness, and surface density (for observations over ice).

  12. L-Band Ionosphere Scintillations Observed by A Spaced GPS Receiver Array during Recent Active Experiments at HAARP

    NASA Astrophysics Data System (ADS)

    Morton, Y.; Pelgrum, W.; van Graas, F.; Gunawardena, S.; Charney, D.; Peng, S.; Triplett, J.; Vikram, P.; Vemuru, A.

    2010-12-01

    L-Band Ionosphere Scintillations Observed by A Spaced GPS Receiver Array during Recent Active Experiments at HAARP Jade Morton*, Wouter Pelgrum**, Sanjeev Gunawardena**, Frank van Graas**, Dan Charney*, Senlin Peng***, Jeff Triplett*, Ajay Vemuru** * Department of Electrical and Computer Engineering, Miami University ** Avionics Engineering Center, Ohio University *** Department of Electrical and Computer Engineering, Virginia Tech Ionosphere irregularities can cause scintillation of satellite-based radio communication, navigation, and surveillance signals. While these scintillation effects will impact the corresponding receiver and system performance, carefully recovered signal parameters serve as a means of studying the background state and dynamics of the ionosphere. In this presentation, we will describe our recent effort in establishing a unique spaced GNSS receiver array at HAARP, Alaska to collect GPS and GLONASS satellite signals at various stages of the GNSS receiver processing. Preliminary receiver processing results as well as additional on-site diagnostic instrumentation measurements obtained from two active heating experiment campaigns will be presented to demonstrate the feasibility and effectiveness of our experimental data collection system in providing insightful details of ionosphere responses to active perturbations.

  13. Position, Navigation, and Timing: GPS Scientific Applications

    NASA Technical Reports Server (NTRS)

    Neilan, Ruth E.

    2008-01-01

    This slide presentation reviews the development and deployment of the Global Positioning System (GPS). This presentation also includes measuring space and time, GPS as a tool for science, development of high precision JPL GPS receivers, and technology and applications developments.

  14. PMMW/DGPS/GPS integrated situation awareness system

    NASA Astrophysics Data System (ADS)

    Tarleton, Norman G.; Symosek, Peter F.; Hartman, Randy

    1998-07-01

    Integrating Passive Millimeter Wave camera (PMMW), Global Positioning System (GPS), and Differential Global Positioning System (DGPS) provides a pilot with a visual precision approach and landing in inclement weather conditions conceivably down to CAT III conditions. A DARPA funded, NASA Langley managed Technology Reinvestment Program (TRP) consortium consisting of Honeywell, TRW, Boeing, and Composite Optics Corporations is demonstrating the PMMW camera. The TRW developed PMMW camera displays the runway through fog, smoke, and clouds in day or night conditions. The Global Air Traffic Program Office entered into a Cooperative Research and Development Agreement (CRDA) with Honeywell to demonstrate DGPS. The Honeywell developed DGPS provides precision navigational data to within 1 m error where GPS has 100 m of error. In inclement weather the runway approach is initiated using GPS data until a range where DGPS data can be received. The runway is presented to the pilot using the PMMW image viewed via a Heads Up Display (HUD) or Head Mounted Display (HMD). At a range where DGPS data is available, a precise runway and horizon symbology is computed in the Flight Display Computer and overlaid on the PMMW image. Image processing algorithms operate on the PMMW image to identify and highlight obstacles on the runway. The integrated system provides the pilot with an enhanced situation awareness of the runway approach in inclement weather. When a DGPS ground station is not available at the landing area, image processing algorithms (again operating on the PMMW image) generate the runway and horizon symbology. GPS provides the algorithm with initial conditions for runway location and perspective. The algorithm then locates and highlights the runway and any obstacles on the runway. Honeywell Technology Center is performing research in the area of integrating the PMMW, DGPS, and GPS technologies to provide the pilot with the most necessary features of each system; namely

  15. Solar System Modeler: A Distributed, Virtual Environment for Space Visualization and GPS Navigation

    NASA Astrophysics Data System (ADS)

    Williams, Gary E.

    1996-12-01

    The Solar System Modeler (SM) extends the Space Modeler developed in 1994. It provides a virtual environment enabling an explorer to dynamically investigate near Earth satellites, deep space probes, planets, moons, and other celestial phenomena. The explorer navigates the virtual environment via mouse selected options from menu panels while wearing a tracked, head mounted display (HMD). Alternatively, a monitor may replace the HMD and keyboard controls replace head tracking. The SM's functionality is extended by the ability to broadcast simulated GPS satellite transmissions in compliance with Distributed Interactive Simulation (DIS) protocol standards. The transmissions include information found in true GPS broadcasts that is required for a receiver to determine its location. The Virtual GPS Receiver (VGPSR) receives the GPS transmissions from the SM and computes the receiver's position with a realistic error based on numerous variables simulating those encountered in the real GPS system. The VGPSR is designed as a plug-in module for simulations requiring virtual navigation. The receiver's client application provides the VGPSR with the simulation time and the true position of the receiver. In return, the application receives a GPS indicated position.

  16. Robust nonstationary jammer mitigation for GPS receivers with instantaneous frequency error tolerance

    NASA Astrophysics Data System (ADS)

    Wang, Ben; Zhang, Yimin D.; Qin, Si; Amin, Moeness G.

    2016-05-01

    In this paper, we propose a nonstationary jammer suppression method for GPS receivers when the signals are sparsely sampled. Missing data samples induce noise-like artifacts in the time-frequency (TF) distribution and ambiguity function of the received signals, which lead to reduced capability and degraded performance in jammer signature estimation and excision. In the proposed method, a data-dependent TF kernel is utilized to mitigate the artifacts and sparse reconstruction methods are then applied to obtain instantaneous frequency (IF) estimation of the jammers. In addition, an error tolerance of the IF estimate is applied is applied to achieve robust jammer suppression performance in the presence of IF estimation inaccuracy.

  17. The First Experiment with VLBI-GPS Hybrid System

    NASA Technical Reports Server (NTRS)

    Kwak, Younghee; Kondo, Tetsuro; Gotoh, Tadahiro; Amagai, Jun; Takiguchi, Hiroshi; Sekido, Mamoru; Ichikawa, Ryuichi; Sasao, Tetsuo; Cho, Jungho; Kim, Tuhwan

    2010-01-01

    In this paper, we introduce our GPS-VLBI hybrid system and show the results of the first experiment which is now under way. In this hybrid system, GPS signals are captured by a normal GPS antenna, down-converted to IF signals, and then sampled by the VLBI sampler VSSP32 developed by NICT. The sampled GPS data are recorded and correlated in the same way as VLBI observation data. The correlator outputs are the group delay and the delay rate. Since the whole system uses the same frequency standard, many sources of systematic errors are common between the VLBI system and the GPS system. In this hybrid system, the GPS antenna can be regarded as an additional VLBI antenna having multiple beams towards GPS satellites. Therefore, we expect that this approach will provide enough data to improve zenith delay estimates and geodetic results.

  18. The Evolution of Global Positioning System (GPS) Technology.

    ERIC Educational Resources Information Center

    Kumar, Sameer; Moore, Kevin B.

    2002-01-01

    Describes technological advances in the Global Positioning System (GPS), which is also known as the NAVSTAR GPS satellite constellation program developed in 1937, and changes in the nature of our world by GPS in the areas of agriculture, health, military, transportation, environment, wildlife biology, surveying and mapping, space applications, and…

  19. Enhancing the kinematic precise orbit determination of low earth orbiters using GPS receiver clock modelling

    NASA Astrophysics Data System (ADS)

    Yang, Yang; Yue, Xiaokui; Yuan, Jianping; Rizos, Chris

    2014-11-01

    Clock error estimation has been the focus of a great deal of research because of the extensive usage of clocks in GPS positioning applications. The receiver clock error in the spacecraft orbit determination is commonly estimated on an epoch-by-epoch basis, along with the spacecraft’s position. However, due to the high correlation between the spacecraft orbit altitude and the receiver clock parameters, estimates of the radial component are degraded in the kinematic approach. Using clocks with high stability, the predictable behaviour of the receiver oscillator can be exploited to improve the positioning accuracy, especially for the radial component. This paper introduces two GPS receiver clock models to describe the deterministic and stochastic property of the receiver clock, both of which can improve the accuracy of kinematic orbit determination for spacecraft in low earth orbit. In particular, the clock parameters are estimated as time offset and frequency offset in the two-state model. The frequency drift is also estimated as an unknown parameter in the three-state model. Additionally, residual non-deterministic random errors such as frequency white noise, frequency random walk noise and frequency random run noise are modelled. Test results indicate that the positioning accuracy could be improved significantly using one day of GRACE flight data. In particular, the error of the radial component was reduced by over 40.0% in the real-time scenario.

  20. Airborne Antenna System for Minimum-Cycle-Slip GPS Reception

    NASA Technical Reports Server (NTRS)

    Wright, C. Wayne

    2009-01-01

    A system that includes a Global Positioning System (GPS) antenna and associated apparatus for keeping the antenna aimed upward has been developed for use aboard a remote-sensing-survey airplane. The purpose served by the system is to enable minimum- cycle-slip reception of GPS signals used in precise computation of the trajectory of the airplane, without having to restrict the airplane to maneuvers that increase the flight time needed to perform a survey. Cycle slip signifies loss of continuous track of the phase of a signal. Minimum-cycle-slip reception is desirable because maintaining constant track of the phase of the carrier signal from each available GPS satellite is necessary for surveying to centimeter or subcentimeter precision. Even a loss of signal for as short a time as a nanosecond can cause cycle slip. Cycle slips degrade the quality and precision of survey data acquired during a flight. The two principal causes of cycle slip are weakness of signals and multipath propagation. Heretofore, it has been standard practice to mount a GPS antenna rigidly on top of an airplane, and the radiation pattern of the antenna is typically hemispherical, so that all GPS satellites above the horizon are viewed by the antenna during level flight. When the airplane must be banked for a turn or other maneuver, the reception hemisphere becomes correspondingly tilted; hence, the antenna no longer views satellites that may still be above the Earth horizon but are now below the equatorial plane of the tilted reception hemisphere. Moreover, part of the reception hemisphere (typically, on the inside of a turn) becomes pointed toward ground, with a consequent increase in received noise and, therefore, degradation of GPS measurements. To minimize the likelihood of loss of signal and cycle slip, bank angles of remote-sensing survey airplanes have generally been limited to 10 or less, resulting in skidding or slipping uncoordinated turns. An airplane must be banked in order to make

  1. GPS meteorology - Remote sensing of atmospheric water vapor using the Global Positioning System

    NASA Technical Reports Server (NTRS)

    Bevis, Michael; Businger, Steven; Herring, Thomas A.; Rocken, Christian; Anthes, Richard A.; Ware, Randolph H.

    1992-01-01

    We present a new approach to remote sensing of water vapor based on the Global Positioning System (GPS). Geodesists and geophysicists have devised methods for estimating the extent to which signals propagating from GPS satellites to ground-based GPS receivers are delayed by atmospheric water vapor. This delay is parameterized in terms of a time-varying zenith wet delay (ZWD) which is retrieved by stochastic filtering of the GPS data. Given surface temperature and pressure readings at the GPS receiver, the retrieved ZWD can be transformed with very little additional uncertainty into an estimate of the integrated water vapor (IWV) overlying that receiver. Networks of continuously operating GPS receivers are being constructed by geodesists, geophysicists, and government and military agencies, in order to implement a wide range of positioning capabilities. These emerging GPS networks offer the possibility of observing the horizontal distribution of IWV or, equivalently, precipitate water with unprecedented coverage and a temporal resolution of the order of 10 min. These measurements could be utilized in operational weather forecasting and in fundamental research into atmospheric storm systems, the hydrologic cycle, atmospheric chemistry, and global climate change.

  2. Real-time differential GPS/GLONASS trials in Europe using all-in-view 20-channel receivers

    NASA Astrophysics Data System (ADS)

    Capaccio, S.; Lowe, D.; Walsh, D. M. A.; Daly, P.

    Following the initial development of 20-channel, all-in-view Global Navigation Satellite System (GNSS), GPS/GLONASS/Inmarsat-3, receivers at the Institute of Satellite Navigation (ISN), University of Leeds, a modification programme has been undertaken to allow real-time differential corrections to be sent from one 20-channel receiver to another identical receiver using a serial link between them. The differential correction software incorporates the RTCM SC-104 and RTCA DO-217 format developed specifically for GPS and adjusted by the ISN to allow simultaneous GLONASS operation.After successful laboratory testing, real-time differential GNSS tests were successfully completed in static mode between Aberdeen and Leeds via the SkyFix differential data-link, and in dynamic mode at DTEO Boscombe Down using a C-band data-link between the ground and a receiver on board the DRA BAC 1-11 aircraft. The aims of the tests were, (i) to demonstrate real-time differential GNSS position-fixing, (ii) to establish the accuracy improvements brought about, and (iii) to examine the effects of data-link latency and satellite PDOP on the solution accuracy.

  3. The nature of GPS differential receiver bias variability: An examination in the polar cap region

    NASA Astrophysics Data System (ADS)

    Themens, David R.; Jayachandran, P. T.; Langley, Richard B.

    2015-09-01

    While modern GPS receiver differential code bias estimation techniques have become highly refined, they still demonstrate unphysical behavior, namely, notable solar cycle variability. This study investigates the nature of these seasonal and solar cycle bias variabilities in the polar cap region using single-station bias estimation methods. It is shown that the minimization of standard deviation bias estimation technique is linearly dependent on the user's choice of shell height, where the sensitivity of this dependence varies significantly from 1 total electron content unit (1 TECU = 1016 el m-2) per 4000 km in solar minimum winter to in excess of 1 TECU per 90 km during solar maximum summer. Using an ionosonde, we find appreciable shell height variability resulting in bias variabilities of up to 2 TECU. Comparing northward face Resolute Incoherent Scatter Radar (RISR-N) measurements to a collocated GPS station, we find that RISR-derived GPS receiver biases vary seasonally but not with solar cycle. RMS differences between bias estimation methods and observation between 2009 and 2013 were found to range from 2.7 TECU to 3.4 TECU, depending on method. To account for the erroneous solar cycle variability of standard bias estimation approaches, we linearly fit these biases to sunspot number, removing the trend. RMS errors after sunspot detrending these biases are reduced to 1.91 TECU. Also, these ISR-derived and sunspot-detrended biases are fit to ambient temperature, where a significant correlation is found. By using these temperature-fitted biases we further reduce RMS errors to 1.66 TECU. These results can be taken as further evidence of temperature-dependent dispersion in the GPS cabling and antenna hardware.

  4. Experimental validation of GPS-INS-STAR hybrid navigation system for space autonomy

    NASA Astrophysics Data System (ADS)

    Tanabe, Toru; Harigae, Masatoshi

    The experimental validation of the GPS-INS-STAR hybrid navigation system concept is performed. The hybrid navigation system combines the best features of employed sensors to improve total navigation performances. The GPS-INS-STAR hybrid navigation system consists of the three different sensors, a GPS receiver, an inertial navigation system and a STAR image sensor. In this concept, the system integrates a high positioning performance of the GPS system, an accurate attitude determination capability of the STAR image sensor and the INS signal with a wide bandwidth. It results in a complete 6-DOF (degrees of freedom) autonomous navigation system. The present paper shows the validation of the concept by the experiments using GPS, INS and STAR hardware systems. The experiments are divided into three steps. Firstly, the INS-STAR hybrid navigation system is constructed on the 3-axis motion table to verify the performances of its attitude loop. Secondly, the GPS-INS hybrid navigation system installed on the car shows the performance improvement in its translational loop. Finally, the full configuration of the GPS-INS-STAR hybrid navigation system is evaluated at night. Each experiment result is checked by the theoretical analysis. In the theoretical analysis, the concept of observability well explains the performances of the system. Its feasibility for space application is also evaluated in the point of existing hardware technology. It is concluded that the experiments vaidate the concept of the hybrid navigation system and confirm its capability to realize space autonomy.

  5. Studying Convective Events Over Southern Arizona by Using Ground GPS Receivers and Cloud to Ground Lightning

    NASA Astrophysics Data System (ADS)

    Orduño, A. M.; Sosa, C. M.; Jacobo, R. A.

    2013-05-01

    Over the last decades, Global Position System (GPS) satellites have been used for in various fields of the Earth Sciences. In particular, "GPS Meteorology" was born in the attempt to retrieve water vapor, specifically column-integrated water vapor or, precipitable water vapor (PWV), that results from the noise induced by the atmosphere in the GPS signal. Monitoring PWV with GPS is relatively inexpensive, works under all weather conditions, and has a high time resolution which complements traditional techniques such as radiosondes and satellite-based retrievals. The North American Monsoon (NAM) is a seasonal system that affects the southwestern of United States and northwestern Mexico. Atmospheric Water Vapor is transported from the Gulf of California, Pacific Ocean and the Gulf of Mexico to the continental areas and this contribute to the genesis of convective systems that develop over this region. In many cases, these systems are characterized by relatively short lifetimes, a great amount of precipitation accompanied with lightning making it difficult to study with radiosondes, given their limited time resolution (operationally twice a day). On the other hand, GOES satellite has better time resolution (one hour), but does not provide water vapor in cloudy conditions, precisely when the data are needed. This makes GPS a great tool to study deep atmospheric convection over during the NAM. During the monsoon season 2002 and 2003, we noted that local GPS and the radiosondes launched in Tucson, Arizona showed, for some cases, a significant discrepancy in their PWV estimation. In determining the causes of these discrepancies we discovered that the GPS was detecting convective events in its vicinity that the radiosondes could not detect, a strength that had not considered before. Convective activity in Southern Arizona often produces gust fronts that result in dramatic changes of temperature and humidity. These gust fronts also generate a shift in wind direction and

  6. Automated daily processing of more than 1000 ground-based GPS receivers for studying intense ionospheric storms

    NASA Technical Reports Server (NTRS)

    Komjathy, Attila; Sparks, Lawrence; Wilson, Brian D.; Mannucci, Anthony J.

    2005-01-01

    To take advantage of the vast amount of GPS data, researchers use a number of techniques to estimate satellite and receiver interfrequency biases and the total electron content (TEC) of the ionosphere. Most techniques estimate vertical ionospheric structure and, simultaneously, hardware-related biases treated as nuisance parameters. These methods often are limited to 200 GPS receivers and use a sequential least squares or Kalman filter approach. The biases are later removed from the measurements to obtain unbiased TEC. In our approach to calibrating GPS receiver and transmitter interfrequency biases we take advantage of all available GPS receivers using a new processing algorithm based on the Global Ionospheric Mapping (GIM) software developed at the Jet Propulsion Laboratory. This new capability is designed to estimate receiver biases for all stations. We solve for the instrumental biases by modeling the ionospheric delay and removing it from the observation equation using precomputed GIM maps. The precomputed GIM maps rely on 200 globally distributed GPS receivers to establish the ''background'' used to model the ionosphere at the remaining 800 GPS sites.

  7. Multipath effects in a Global Positioning Satellite system receiver

    NASA Technical Reports Server (NTRS)

    Mcdonald, Malcolm W.

    1992-01-01

    This study, as a part of a large continuing investigation being conducted by the Communications Systems Branch of the Information and Electronic Systems Laboratory at the Marshall Space Flight Center, was undertaken to explore the multipath response characteristics of a particular Global Positioning Satellite (GPS) receiver which was available in the laboratory at the beginning and throughout the entirety of the study, and to develop a suitable regime of experimental procedure which can be applied to other state-of-the-art GPS receivers in the larger investigation.

  8. System and method for generating attitude determinations using GPS

    NASA Technical Reports Server (NTRS)

    Cohen, Clark E. (Inventor)

    1996-01-01

    A GPS attitude receiver for determining the attitude of a moving vehicle in conjunction with a first, a second, a third, and a fourth antenna mounted to the moving vehicle. Each of the antennas receives a plurality of GPS signals that each include a carrier component. For each of the carrier components of the received GPS signals there is an integer ambiguity associated with the first and fourth antennas, an integer ambiguity associated with second and fourth antennas, and an integer ambiguity associated with the third and fourth antennas. The GPS attitude receiver measures phase values for the carrier components of the GPS signals received from each of the antennas at a plurality of measurement epochs during an initialization period and at a measurement epoch after the initialization period. In response to the phase values measured at the measurement epochs during the initialization period, the GPS attitude receiver computes integer ambiguity resolution values representing resolution of the integer ambiguities. Then, in response to the computed integer ambiguity resolution values and the phase value measured at the measurement epoch after the initialization period, it computes values defining the attitude of the moving vehicle at the measurement epoch after the initialization period.

  9. NASA's global differential GPS system and the TDRSS augmentation service for satellites

    NASA Technical Reports Server (NTRS)

    Bar-Sever, Yoaz; Young, Larry; Stocklin, Frank; Rush, John

    2004-01-01

    NASA is planning to launch a new service for Earth satellites providing them with precise GPS differential corrections and other ancillary information enabling decimeter level orbit determination accuracy, and nanosecond time-transfer accuracy, onboard, in real-time. The TDRSS Augmentation Service for Satellites (TASS) will broadcast its message on the S-band multiple access channel of NASA's Tracking and Data Relay Satellite System (TDRSS). The satellite's phase array antenna has been configured to provide a wide beam, extending coverage up to 1000 km altitude over the poles. Global coverage will be ensured with broadcast from three or more TDRSS satellites. The GPS differential corrections are provided by the NASA Global Differential GPS (GDGPS) System, developed and operated by NASA's Jet Propulsion Laboratory. The GDGPS System employs a global ground network of more than 70 GPS receivers to monitor the GPS constellation in real time. The system provides real-time estimates of the GPS satellite states, as well as many other real-time products such as differential corrections, global ionospheric maps, and integrity monitoring. The unique multiply redundant architecture of the GDGPS System ensures very high reliability, with 99.999% demonstrated since the inception of the system in Early 2000. The estimated real time GPS orbit and clock states provided by the GDGPS system are accurate to better than 20 cm 3D RMS, and have been demonstrated to support sub-decimeter real time positioning and orbit determination for a variety of terrestrial, airborne, and spaceborne applications. In addition to the GPS differential corrections, TASS will provide real-time Earth orientation and solar flux information that enable precise onboard knowledge of the Earth-fixed position of the spacecraft, and precise orbit prediction and planning capabilities. TASS will also provide 5 seconds alarms for GPS integrity failures based on the unique GPS integrity monitoring service of the

  10. The clock-aided RAIM method and it's application in improving the positioning precision of GPS receiver

    NASA Astrophysics Data System (ADS)

    Shi, Yibing; Teng, Yunlong

    2012-08-01

    The prediction precision of receiver clock bias (RCB) is an important factor in influencing the receiver autonomous integrity monitoring (RAIM) method augmented with it and improving GPS receiver positioning precision. According to the characters of the RCB series, a new prediction model in discrete grey form is presented in this paper, and then the initial value of the model is determined by establishing unconstrained optimised formula. The prediction model is utilised to augment RAIM method in order to identify faulty satellite and improve the positioning precision of GPS receiver. Experimental results show that the prediction model is fit for predicting the RCB series, and the RAIM method aided by it is feasible. The auxiliary RAIM method can not only enhance the efficiency of identifying faulty satellite, but also improve the positioning precision of GPS receiver obviously.

  11. First Results of Field Absolute Calibration of the GPS Receiver Antenna at Wuhan University.

    PubMed

    Hu, Zhigang; Zhao, Qile; Chen, Guo; Wang, Guangxing; Dai, Zhiqiang; Li, Tao

    2015-01-01

    GNSS receiver antenna phase center variations (PCVs), which arise from the non-spherical phase response of GNSS signals have to be well corrected for high-precision GNSS applications. Without using a precise antenna phase center correction (PCC) model, the estimated position of a station monument will lead to a bias of up to several centimeters. The Chinese large-scale research project "Crustal Movement Observation Network of China" (CMONOC), which requires high-precision positions in a comprehensive GPS observational network motived establishment of a set of absolute field calibrations of the GPS receiver antenna located at Wuhan University. In this paper the calibration facilities are firstly introduced and then the multipath elimination and PCV estimation strategies currently used are elaborated. The validation of estimated PCV values of test antenna are finally conducted, compared with the International GNSS Service (IGS) type values. Examples of TRM57971.00 NONE antenna calibrations from our calibration facility demonstrate that the derived PCVs and IGS type mean values agree at the 1 mm level. PMID:26580616

  12. First Results of Field Absolute Calibration of the GPS Receiver Antenna at Wuhan University

    PubMed Central

    Hu, Zhigang; Zhao, Qile; Chen, Guo; Wang, Guangxing; Dai, Zhiqiang; Li, Tao

    2015-01-01

    GNSS receiver antenna phase center variations (PCVs), which arise from the non-spherical phase response of GNSS signals have to be well corrected for high-precision GNSS applications. Without using a precise antenna phase center correction (PCC) model, the estimated position of a station monument will lead to a bias of up to several centimeters. The Chinese large-scale research project “Crustal Movement Observation Network of China” (CMONOC), which requires high-precision positions in a comprehensive GPS observational network motived establishment of a set of absolute field calibrations of the GPS receiver antenna located at Wuhan University. In this paper the calibration facilities are firstly introduced and then the multipath elimination and PCV estimation strategies currently used are elaborated. The validation of estimated PCV values of test antenna are finally conducted, compared with the International GNSS Service (IGS) type values. Examples of TRM57971.00 NONE antenna calibrations from our calibration facility demonstrate that the derived PCVs and IGS type mean values agree at the 1 mm level. PMID:26580616

  13. Autonomous navigation system based on GPS and magnetometer data

    NASA Technical Reports Server (NTRS)

    Julie, Thienel K. (Inventor); Richard, Harman R. (Inventor); Bar-Itzhack, Itzhack Y. (Inventor)

    2004-01-01

    This invention is drawn to an autonomous navigation system using Global Positioning System (GPS) and magnetometers for low Earth orbit satellites. As a magnetometer is reliable and always provides information on spacecraft attitude, rate, and orbit, the magnetometer-GPS configuration solves GPS initialization problem, decreasing the convergence time for navigation estimate and improving the overall accuracy. Eventually the magnetometer-GPS configuration enables the system to avoid costly and inherently less reliable gyro for rate estimation. Being autonomous, this invention would provide for black-box spacecraft navigation, producing attitude, orbit, and rate estimates without any ground input with high accuracy and reliability.

  14. Receiver clock stability - An important aid in the GPS integrity problem

    NASA Astrophysics Data System (ADS)

    McBurney, Paul W.; Brown, R. Grover

    It is well known that the stability of the GPS receiver clock can be used to help 'coast' through periods of high GDOP. A somewhat analogous situation applies when the receiver is attempting to detect slow or incipient satellite failures. The clock, through its stability, provides an additional measurement which slowly degrades with time, but nevertheless provides the needed redundancy for failure detection. The geometric circumstances giving rise to the need for clock coasting are more complicated for failure detection than in the simple navigation problem. This is discussed in the paper. Also, a Kalman filter failure detection scheme which automatically accomplishes the needed clock coasting is presented. Finally, results of Monte Carlo simulations demonstrating the effectiveness of the scheme in both detecting and isolating the errant satellite are given in the paper.

  15. Flight evaluation of differential GPS aided inertial navigation systems

    NASA Technical Reports Server (NTRS)

    Mcnally, B. David; Paielli, Russell A.; Bach, Ralph E., Jr.; Warner, David N., Jr.

    1992-01-01

    Algorithms are described for integration of Differential Global Positioning System (DGPS) data with Inertial Navigation System (INS) data to provide an integrated DGPS/INS navigation system. The objective is to establish the benefits that can be achieved through various levels of integration of DGPS with INS for precision navigation. An eight state Kalman filter integration was implemented in real-time on a twin turbo-prop transport aircraft to evaluate system performance during terminal approach and landing operations. A fully integrated DGPS/INS system is also presented which models accelerometer and rate-gyro measurement errors plus position, velocity, and attitude errors. The fully integrated system was implemented off-line using range-domain (seventeen-state) and position domain (fifteen-state) Kalman filters. Both filter integration approaches were evaluated using data collected during the flight test. Flight-test data consisted of measurements from a 5 channel Precision Code GPS receiver, a strap-down Inertial Navigation Unit (INU), and GPS satellite differential range corrections from a ground reference station. The aircraft was laser tracked to determine its true position. Results indicate that there is no significant improvement in positioning accuracy with the higher levels of DGPS/INS integration. All three systems provided high-frequency (e.g., 20 Hz) estimates of position and velocity. The fully integrated system provided estimates of inertial sensor errors which may be used to improve INS navigation accuracy should GPS become unavailable, and improved estimates of acceleration, attitude, and body rates which can be used for guidance and control. Precision Code DGPS/INS positioning accuracy (root-mean-square) was 1.0 m cross-track and 3.0 m vertical. (This AGARDograph was sponsored by the Guidance and Control Panel.)

  16. New GPS Network on the Active Fault System in Taiwan

    NASA Astrophysics Data System (ADS)

    Hou, C.; Chen, Y.; Hu, J.; Lin, C.; Chen, C.; Wang, J.; Chung, L.; Chung, W.; Hsieh, C.; Chen, Y.

    2004-12-01

    According to the historical records, disastrous earthquakes occurred in Taiwan were caused by reactivations of active faults. In last century, there were five with the surface rupture: 1906 Meishan Eq. (the Meishan F.), 1935 Hsihchu Eq. (the Shihtan and the Tuntzuchiao F.), 1946 Hsinhua Eq. (Hsinhua F.), 1951 Hualien-Taitung Eq. (Longitudinal Valley F.), and 1999 Chi-Chi Eq. (the Chelungpu F.). In order to identify earthquake associated surface rupture and further to mitigate potential hazards, the investigation and monitoring on the active fault system are of great urgency. Central Geological Survey (CGS) of Taiwan is currently executing a 5-year (2002-2006) project, integrating geological and geodetic data to better characterize short-term and long-term spatial and temporal variations in deformation across major already-known active faults of Taiwan. For the former, we use field survey, drilling, geophysical exploration, and trenching to recognize the long-term slip rate and recurrence interval of each fault. For the latter, we deploy near-fault campaign-style GPS and leveling monitoring networks. Here we further combine the result of other GPS networks including continuous-mode. This project is actually concentrated on fault-specific investigation.. Until Dec. 2004, we have set up 756 GPS stations and 27 precise leveling lines including 1024 leveling benchmarks. For the purpose of understanding temporal variability and receive continuous record, the CGS began to deploy 6~10 new GPS stations of continuous mode since 2004. Upon the completion of the geodetic project, we are supposed to provide information on short-term slip rates of major active faults. By integrating other geological datasets we will also evaluate the short-term and long-term behavior of the active faults, and further offer insight into spatial and temporal variability in deformation processes.

  17. A Novel Method for Precise Onboard Real-Time Orbit Determination with a Standalone GPS Receiver

    PubMed Central

    Wang, Fuhong; Gong, Xuewen; Sang, Jizhang; Zhang, Xiaohong

    2015-01-01

    Satellite remote sensing systems require accurate, autonomous and real-time orbit determinations (RTOD) for geo-referencing. Onboard Global Positioning System (GPS) has widely been used to undertake such tasks. In this paper, a novel RTOD method achieving decimeter precision using GPS carrier phases, required by China’s HY2A and ZY3 missions, is presented. A key to the algorithm success is the introduction of a new parameter, termed pseudo-ambiguity. This parameter combines the phase ambiguity, the orbit, and clock offset errors of the GPS broadcast ephemeris together to absorb a large part of the combined error. Based on the analysis of the characteristics of the orbit and clock offset errors, the pseudo-ambiguity can be modeled as a random walk, and estimated in an extended Kalman filter. Experiments of processing real data from HY2A and ZY3, simulating onboard operational scenarios of these two missions, are performed using the developed software SATODS. Results have demonstrated that the position and velocity accuracy (3D RMS) of 0.2–0.4 m and 0.2–0.4 mm/s, respectively, are achieved using dual-frequency carrier phases for HY2A, and slightly worse results for ZY3. These results show it is feasible to obtain orbit accuracy at decimeter level of 3–5 dm for position and 0.3–0.5 mm/s for velocity with this RTOD method. PMID:26690149

  18. A Novel Method for Precise Onboard Real-Time Orbit Determination with a Standalone GPS Receiver.

    PubMed

    Wang, Fuhong; Gong, Xuewen; Sang, Jizhang; Zhang, Xiaohong

    2015-01-01

    Satellite remote sensing systems require accurate, autonomous and real-time orbit determinations (RTOD) for geo-referencing. Onboard Global Positioning System (GPS) has widely been used to undertake such tasks. In this paper, a novel RTOD method achieving decimeter precision using GPS carrier phases, required by China's HY2A and ZY3 missions, is presented. A key to the algorithm success is the introduction of a new parameter, termed pseudo-ambiguity. This parameter combines the phase ambiguity, the orbit, and clock offset errors of the GPS broadcast ephemeris together to absorb a large part of the combined error. Based on the analysis of the characteristics of the orbit and clock offset errors, the pseudo-ambiguity can be modeled as a random walk, and estimated in an extended Kalman filter. Experiments of processing real data from HY2A and ZY3, simulating onboard operational scenarios of these two missions, are performed using the developed software SATODS. Results have demonstrated that the position and velocity accuracy (3D RMS) of 0.2-0.4 m and 0.2-0.4 mm/s, respectively, are achieved using dual-frequency carrier phases for HY2A, and slightly worse results for ZY3. These results show it is feasible to obtain orbit accuracy at decimeter level of 3-5 dm for position and 0.3-0.5 mm/s for velocity with this RTOD method. PMID:26690149

  19. Localized three-dimensional ionospheric tomography with GPS ground receiver measurements

    NASA Astrophysics Data System (ADS)

    Lee, Jeffrey K.; Kamalabadi, Farzad; Makela, Jonathan J.

    2007-08-01

    This paper describes a technique for 3-D tomographic imaging of the ionosphere with high spatial resolution (75 to 95 km in latitude/longitude and 30 km in altitude). The total electron content (TEC) values are derived from dual-frequency measurements obtained from GPS satellites by ground-based receivers. When available, ionosonde data are used to construct a priori vertical profiles modeled using Chapman functions. Two regularization algorithms are investigated for tomographic image reconstruction: Tikhonov and Total Variation (TV), corresponding to quadratic and l1 norm minimizations of the penalty constraint, respectively. The TV method is used because it generally preserves discontinuities in the image effectively and is more resistant to noise. By contrast, Tikhonov, or quadratic, regularization tends to oversmooth image structures and discontinuities. However, a closed-form solution of the TV method does not exist and so performance depends heavily on numerical optimization techniques, which are nontrivial to implement because the inverse problem is both ill-posed and ill-conditioned. We also apply regularization parameter-selection methods to demonstrate their applicability in our study. The algorithms are demonstrated using real GPS TEC measurements from an observation geometry centered in southern California. We demonstrate the performance of these techniques under quiet, midlatitude conditions. The resulting reconstructions reasonably determine the shape of the ionospheric profile. Artifacts can potentially appear near voxels with no raypath information, which is directly related to the sparseness and nonuniform distribution of the GPS raypaths. We discuss some methods to constrain the solution to realistic bounds.

  20. Rip current monitoring using GPS buoy system

    NASA Astrophysics Data System (ADS)

    Song, DongSeob; Kim, InHo; Kang, DongSoo

    2014-05-01

    The occurrence of rip current in the Haeundae beach, which is one of the most famous beaches in South Korea, has been threatening beach-goers security in summer season annually. Many coastal scientists have been investigating rip currents by using field observations and measurements, laboratory measurements and wave tank experiments, and computer and numerical modeling. Rip current velocity is intermittent and may rapidly increase within minutes due to larger incoming wave groups or nearshore circulation instabilities. It is important to understand that changes in rip current velocity occur in response to changes in incoming wave height and period as well as changes in water level. GPS buoys have been used to acquire sea level change data, atmospheric parameters and other oceanic variables in sea for the purposes of vertical datum determination, tide correction, radar altimeter calibration, ocean environment and marine pollution monitoring. Therefore, we adopted GPS buoy system for an experiment which is to investigate rip current velocity; it is sporadic and may quickly upsurge within minutes due to larger arriving wave groups or nearshore flow uncertainties. In this study, for high accurate positioning of buy equipment, a Satellite Based Argumentation System DGPS data logger was deployed to investigate within floating object, and it can be acquired three-dimensional coordinate or geodetic position of buoy with continuous NMEA-0183 protocol during 24 hours. The wave height measured by in-situ hydrometer in a cross-shore array clearly increased before and after occurrence of rip current, and wave period also was lengthened around an event. These results show that wave height and period correlate reasonably well with long-shore current interaction in the Haeundae beach. Additionally, current meter data and GPS buoy data showed that rip current velocities, about 0.2 m/s, may become dangerously strong under specific conditions. Acknowledgement This research was

  1. Evaluating the velocity accuracy of an integrated GPS/INS system: Flight test results

    SciTech Connect

    Owen, T.E.; Wardlaw, R.

    1991-12-31

    Verifying the velocity accuracy of a GPS receiver or an integrated GPS/INS system in a dynamic environment is a difficult proposition when many of the commonly used reference systems have velocity uncertainities of the same order of magnitude or greater than the GPS system. The results of flight tests aboard an aircraft in which multiple reference systems simultaneously collected data to evaluate the accuracy of an integrated GPS/INS system are reported. Emphasis is placed on obtaining high accuracy estimates of the velocity error of the integrated system in order to verify that velocity accuracy is maintained during both linear and circular trajectories. Three different reference systems operating in parallel during flight tests are used to independently determine the position and velocity of an aircraft in flight. They are a transponder/interrogator ranging system, a laser tracker, and GPS carrier phase processing. Results obtained from these reference systems are compared against each other and against an integrated real time differential based GPS/INS system to arrive at a set of conclusions about the accuracy of the integrated system.

  2. A Low Cost GPS System for Real-Time Tracking of Sounding Rockets

    NASA Technical Reports Server (NTRS)

    Markgraf, M.; Montenbruck, O.; Hassenpflug, F.; Turner, P.; Bull, B.; Bauer, Frank (Technical Monitor)

    2001-01-01

    This paper describes the development as well as the on-ground and the in-flight evaluation of a low cost Global Positioning System (GPS) system for real-time tracking of sounding rockets. The flight unit comprises a modified ORION GPS receiver and a newly designed switchable antenna system composed of a helical antenna in the rocket tip and a dual-blade antenna combination attached to the body of the service module. Aside from the flight hardware a PC based terminal program has been developed to monitor the GPS data and graphically displays the rocket's path during the flight. In addition an Instantaneous Impact Point (IIP) prediction is performed based on the received position and velocity information. In preparation for ESA's Maxus-4 mission, a sounding rocket test flight was carried out at Esrange, Kiruna, on 19 Feb. 2001 to validate existing ground facilities and range safety installations. Due to the absence of a dedicated scientific payload, the flight offered the opportunity to test multiple GPS receivers and assess their performance for the tracking of sounding rockets. In addition to the ORION receiver, an Ashtech G12 HDMA receiver and a BAE (Canadian Marconi) Allstar receiver, both connected to a wrap-around antenna, have been flown on the same rocket as part of an independent experiment provided by the Goddard Space Flight Center. This allows an in-depth verification and trade-off of different receiver and antenna concepts.

  3. Observability and performance analysis of integrated GPS/INS navigation systems

    NASA Astrophysics Data System (ADS)

    Shao, Yunfeng

    This primary objective of this thesis is to analyze the performance and observability characteristics of integrated navigation systems which fuse the information from the Global Positioning System (GPS) and Inertial Navigation Systems (INS) of varying quality. It is shown that INS output error characteristics affect the notion of observability with these systems. More specifically; it is shown that when INS sensor quality is low, the traditional metrics of deterministic and stochastic observability are incomplete metrics to describe the system performance. Accordingly, a new metric as well as detailed trade study results that characterize the observability of GPS/INS fusion filter which use low quality inertial sensors is developed. A secondary objective of this thesis is to evaluate the use of an integrated GPS/INS system in two aviation applications of significant current interest. The first application is about monitoring and mitigating the impact of structural flexure of an aircraft carrier which is he host of the GPS-based landing system known as Joint Precision Approach and Landing Systems (JPALS). A mathematic error model is developed and validated using experimental ship motion data. The second application is that of checking the integrity of the GPS signal used in GPS-based landing systems such as JPALS and other landing systems envisioned for future use in commercial aviation. An inertial aided Receiver Autonomous Integrity Monitoring (RAIM) algorithm is designed and its performance improvements with inertial aiding are quantified.

  4. Determining slack tide with a GPS receiver on an anchored buoy

    NASA Astrophysics Data System (ADS)

    Valk, M.; Savenije, H. H. G.; Tiberius, C. C. J. M.; Luxemburg, W. M. J.

    2014-07-01

    In this paper we present a novel method to determine the time of occurrence of tidal slack with a GPS receiver mounted on an anchored buoy commonly used to delineate shipping lanes in estuaries and tidal channels. Slack tide occurs when the tide changes direction from ebb to flood flow or from flood to ebb. The determination of this point in time is not only useful for shipping and salvaging, it is also important information for calibrating tidal models, for determining the maximum salt intrusion and for the further refinement of the theory on tidal propagation. The accuracy of the timing is well within 10 min and the method - able to operate in real time - is relatively cheap and easy to implement on a permanent basis or in short field campaigns.

  5. Determining slack tide with a GPS receiver on an anchored buoy

    NASA Astrophysics Data System (ADS)

    Valk, M.; Savenije, H. H. G.; Tiberius, C. C. J. M.; Luxemburg, W. M. J.

    2013-11-01

    In this paper we present a novel method to determine the time of occurrence of tidal slack with a GPS receiver mounted on an anchored buoy commonly used to delineate shipping lanes in estuaries and tidal channels. Slack tide occurs when the tide changes direction from ebb to flood flow, or from flood to ebb. The determination of this point in time is not only useful for shipping and salvaging, it is also important information for calibrating tidal models, for determining the maximum salt intrusion and for the further refinement of the theory on tidal propagation. The accuracy of the timing is well within 10 min and the method - able to operate in real-time - is relatively cheap and easy to implement on a permanent basis or in short field campaigns.

  6. Selecting the optimum telemetry tracking antenna for receiving translated GPS signals

    NASA Astrophysics Data System (ADS)

    Turner, William C.

    Three dual-channel circularly polarized antennas considered for receiving translated GPS signals were tested for feed-induced phase-noise performance. The tested specimens were: (1) a 12-ft diam. reflector with the 15-in diam. Symetrics feed having a scan rate of 21 Hz; (2) a 4-ft diam. reflector with the 7.5-in diam. Radscan type feed, having a scan rate of 29 Hz; and (3) a 4-ft diam. reflector utilizing an EMP single-axis single-channel monopulse S-band feed having a 10 by 4-in. ground plane. Of the three specimens tested, only the Symetrics antenna had any measurable phase noise on the boresight axis. The Radscan antenna outperformed the Symetric antenna in every parameter, primarily because the Radscan employs an open-ended waveguide which has a uniform phase front across its aperture. The Radscan antenna produces no phase noise even at large tracking bias.

  7. Strategies for Near Real Time Estimates of Precipitable Water Vapor from GPS Ground Receivers

    NASA Technical Reports Server (NTRS)

    Y., Bar-Sever; Runge, T.; Kroger, P.

    1995-01-01

    GPS-based estimates of precipitable water vapor (PWV) may be useful in numerical weather models to improve short-term weather predictions. To be effective in numerical weather prediction models, GPS PWV estimates must be produced with sufficient accuracy in near real time. Several estimation strategies for the near real time processing of GPS data are investigated.

  8. A comparison of four precise global positioning system geodetic receivers

    NASA Technical Reports Server (NTRS)

    Goad, C. C.; Sims, M. L.; Young, L. E.

    1985-01-01

    Four precise global positioning system (GPS) geodetic receivers were operated simultaneously in January and February 1984 over ten baselines ranging in distance from 13 to 1304 km. Several of the baselines had been previously measured using very long baseline interferometry and, therefore, provide very good standards to which the satellite results can be compared. Results of these experiments are presented along with a brief description of each receiver and the associated analysis techniques.

  9. Change in refractivity of the atmosphere and large variation in TEC associated with some earthquakes, observed from GPS receiver

    NASA Astrophysics Data System (ADS)

    Karia, S. P.; Pathak, K. N.

    2011-03-01

    The present study reports the analysis of GPS based TEC for our station Surat (21.16°N, 72.78°E) located at the northern crest of equatorial anomaly region in India at times close to some earthquake events (M ⩾ 5) during the year 2009 in India and its neighbouring regions. The TEC data used in the study are obtained from GPS Ionospheric Scintillation and TEC Monitoring (GISTM) system. The TEC data has been analysed corresponding to 11 earthquakes in low solar activity period and quiet geomagnetic condition. We found that, out of 11 cases of earthquakes (M > 5) there were seven cases in which enhancement in TEC occurred on earthquake day and in other four cases there was depletion in TEC on earthquake day. The variation in refractivity prior to earthquake was significant for the cases in which the epicentre lied within a distance of 600 km from the receiving station. By looking into the features on temporal enhancement and depletion of TEC a prediction was made 3-2 days prior to an earthquake (on 28 October 2009 in Bhuj - India). The paper includes a brief discussion on the method of potentially identifying an impending earthquake from ionospheric data.

  10. The GPS integrated navigation and attitude-determination system (GINAS)

    NASA Astrophysics Data System (ADS)

    Lucas, R.; Martin-Neira, M.

    When the European Columbus Free-Flying Laboratory is orbiting the earth at a speed of 7 km/s, the Global Positioning System (GPS) will allow its instantaneous position to be determined on-board, independently of the ground, to an accuracy of better than 100 m. When the European spaceplane Hermes and the Columbus elements are performing rendezvous maneuvers, they will also be relying on GPS measurements to compute the remaining distance to contact. For the first flight of Hermes itself, there will be no pilot on board and GPS-based navigation will be used for this first mission and the landing. This paper describes the results of GPS field-measurement experiments conducted at ESTEC's radio-navigation testbed laboratory, including a novel 'GPS integrated navigation and attitude-determination system'.

  11. Precision, accuracy, and application of diver-towed underwater GPS receivers.

    PubMed

    Schories, Dirk; Niedzwiedz, Gerd

    2012-04-01

    Diver-towed global positioning systems (GPS) handhelds have been used for a few years in underwater monitoring studies. We modeled the accuracy of this method using the software KABKURR originally developed by the University of Rostock for fishing and marine engineering. Additionally, three field experiments were conducted to estimate the precision of the method and apply it in the field: (1) an experiment of underwater transects from 5 to 35 m in the Southern Chile fjord region, (2) a transect from 5 to 30 m under extreme climatic conditions in the Antarctic, and (3) an underwater tracking experiment at Lake Ranco, Southern Chile. The coiled cable length in relation to water depth is the main error source besides the signal quality of the GPS under calm weather conditions. The forces used in the model resulted in a displacement of 2.3 m in a depth of 5 m, 3.2 m at a 10-m depth, 4.6 m in a 20-m depth, 5.5 m at a 30-m depth, and 6.8 m in a 40-m depth, when only an additional 0.5 m cable extension was used compared to the water depth. The GPS buoy requires good buoyancy in order to keep its position at the water surface when the diver is trying to minimize any additional cable extension error. The diver has to apply a tensile force for shortening the cable length at the lower cable end. Repeated diving along transect lines from 5 to 35 m resulted only in small deviations independent of water depth indicating the precision of the method for monitoring studies. Routing of given reference points with a Garmin 76CSx handheld placed in an underwater housing resulted in mean deviances less than 6 m at a water depth of 10 m. Thus, we can confirm that diver-towed GPS handhelds give promising results when used for underwater research in shallow water and open a wide field of applicability, but no submeter accuracy is possible due to the different error sources. PMID:21614620

  12. Receiver Clock Modelling for GPS-only Gravity Field Recovery from GRACE

    NASA Astrophysics Data System (ADS)

    Orliac, E.; Jaeggi, A.; Dach, R.; Weinbach, U.; Schoen, S.

    2012-04-01

    Previous results from the authors [1, 2] show that for stations connected to highly stable clocks (H-Maser), kinematic Precise Point Positioning (PPP) solutions for the height component can be highly improved. A reduction of up to 70% of the standard deviation of the kinematic position could be observed if the receiver clock is modelled with a second order polynomial instead of estimating independent epoch-wise clock corrections. Although those initial results are very promising, the applicability of such an approach is rather limited since very stable clocks are hardly portable. The only "truly" kinematic objects carrying a GPS receiver connected to a stable clock are the two GRACE satellites. In this paper we investigate the impact of the deterministic modelling of the receiver clocks in the determination of kinematic positions for the two GRACE satellites. Solutions from both contributing institutions, namely the Astronomical Institute of University of Bern and the Institut für Erdmessung of Leibniz Universität Hannover are considered. Comparisons with standard kinematic and reduced-dynamic orbit solutions will be provided and technical aspects discussed. Finally, based on one month of data, gravity fields from all kinematic solutions are derived and compared. [1] Orliac, E., R. Dach, D. Voithenleitner, U. Hugentobler, K. Wang, M. Rothacher, and D. Svehla (2011). Clock Modeling for GNSS Applications, AGU Fall Meeting 2011, San Francisco, USA, December 5-9, 2011. [2] Weinbach, U., and S. Schön (2011). GNSS receiver clock modeling when using high-precision oscillators and its impact on PPP, J. Adv. Space Res., 47(2):229-238 DOI: 10.1016/j.asr.2010.06.031.

  13. Measuring snow liquid water content with low-cost GPS receivers.

    PubMed

    Koch, Franziska; Prasch, Monika; Schmid, Lino; Schweizer, Jürg; Mauser, Wolfram

    2014-01-01

    The amount of liquid water in snow characterizes the wetness of a snowpack. Its temporal evolution plays an important role for wet-snow avalanche prediction, as well as the onset of meltwater release and water availability estimations within a river basin. However, it is still a challenge and a not yet satisfyingly solved issue to measure the liquid water content (LWC) in snow with conventional in situ and remote sensing techniques. We propose a new approach based on the attenuation of microwave radiation in the L-band emitted by the satellites of the Global Positioning System (GPS). For this purpose, we performed a continuous low-cost GPS measurement experiment at the Weissfluhjoch test site in Switzerland, during the snow melt period in 2013. As a measure of signal strength, we analyzed the carrier-to-noise power density ratio (C/N0) and developed a procedure to normalize these data. The bulk volumetric LWC was determined based on assumptions for attenuation, reflection and refraction of radiation in wet snow. The onset of melt, as well as daily melt-freeze cycles were clearly detected. The temporal evolution of the LWC was closely related to the meteorological and snow-hydrological data. Due to its non-destructive setup, its cost-efficiency and global availability, this approach has the potential to be implemented in distributed sensor networks for avalanche prediction or basin-wide melt onset measurements. PMID:25384007

  14. Measuring Snow Liquid Water Content with Low-Cost GPS Receivers

    PubMed Central

    Koch, Franziska; Prasch, Monika; Schmid, Lino; Schweizer, Jürg; Mauser, Wolfram

    2014-01-01

    The amount of liquid water in snow characterizes the wetness of a snowpack. Its temporal evolution plays an important role for wet-snow avalanche prediction, as well as the onset of meltwater release and water availability estimations within a river basin. However, it is still a challenge and a not yet satisfyingly solved issue to measure the liquid water content (LWC) in snow with conventional in situ and remote sensing techniques. We propose a new approach based on the attenuation of microwave radiation in the L-band emitted by the satellites of the Global Positioning System (GPS). For this purpose, we performed a continuous low-cost GPS measurement experiment at the Weissfluhjoch test site in Switzerland, during the snow melt period in 2013. As a measure of signal strength, we analyzed the carrier-to-noise power density ratio (C/N0) and developed a procedure to normalize these data. The bulk volumetric LWC was determined based on assumptions for attenuation, reflection and refraction of radiation in wet snow. The onset of melt, as well as daily melt-freeze cycles were clearly detected. The temporal evolution of the LWC was closely related to the meteorological and snow-hydrological data. Due to its non-destructive setup, its cost-efficiency and global availability, this approach has the potential to be implemented in distributed sensor networks for avalanche prediction or basin-wide melt onset measurements. PMID:25384007

  15. FPGA-Based Real-Time Embedded System for RISS/GPS Integrated Navigation

    PubMed Central

    Abdelfatah, Walid Farid; Georgy, Jacques; Iqbal, Umar; Noureldin, Aboelmagd

    2012-01-01

    Navigation algorithms integrating measurements from multi-sensor systems overcome the problems that arise from using GPS navigation systems in standalone mode. Algorithms which integrate the data from 2D low-cost reduced inertial sensor system (RISS), consisting of a gyroscope and an odometer or wheel encoders, along with a GPS receiver via a Kalman filter has proved to be worthy in providing a consistent and more reliable navigation solution compared to standalone GPS receivers. It has been also shown to be beneficial, especially in GPS-denied environments such as urban canyons and tunnels. The main objective of this paper is to narrow the idea-to-implementation gap that follows the algorithm development by realizing a low-cost real-time embedded navigation system capable of computing the data-fused positioning solution. The role of the developed system is to synchronize the measurements from the three sensors, relative to the pulse per second signal generated from the GPS, after which the navigation algorithm is applied to the synchronized measurements to compute the navigation solution in real-time. Employing a customizable soft-core processor on an FPGA in the kernel of the navigation system, provided the flexibility for communicating with the various sensors and the computation capability required by the Kalman filter integration algorithm. PMID:22368460

  16. FPGA-based real-time embedded system for RISS/GPS integrated navigation.

    PubMed

    Abdelfatah, Walid Farid; Georgy, Jacques; Iqbal, Umar; Noureldin, Aboelmagd

    2012-01-01

    Navigation algorithms integrating measurements from multi-sensor systems overcome the problems that arise from using GPS navigation systems in standalone mode. Algorithms which integrate the data from 2D low-cost reduced inertial sensor system (RISS), consisting of a gyroscope and an odometer or wheel encoders, along with a GPS receiver via a Kalman filter has proved to be worthy in providing a consistent and more reliable navigation solution compared to standalone GPS receivers. It has been also shown to be beneficial, especially in GPS-denied environments such as urban canyons and tunnels. The main objective of this paper is to narrow the idea-to-implementation gap that follows the algorithm development by realizing a low-cost real-time embedded navigation system capable of computing the data-fused positioning solution. The role of the developed system is to synchronize the measurements from the three sensors, relative to the pulse per second signal generated from the GPS, after which the navigation algorithm is applied to the synchronized measurements to compute the navigation solution in real-time. Employing a customizable soft-core processor on an FPGA in the kernel of the navigation system, provided the flexibility for communicating with the various sensors and the computation capability required by the Kalman filter integration algorithm. PMID:22368460

  17. Accurate aircraft wind measurements using the global positioning system (GPS)

    SciTech Connect

    Dobosy, R.J.; Crawford, T.L., McMillen, R.T., Dumas, E.J.

    1996-11-01

    High accuracy measurements of the spatial distribution of wind speed are required in the study of turbulent exchange between the atmosphere and the earth. The use of a differential global positioning system (GPS) to determine the sensor velocity vector component of wind speed is discussed in this paper. The results of noise and rocking testing are summarized, and fluxes obtained from the GPS-based methods are compared to those measured from systems on towers and airplanes. The GPS-based methods provided usable measurements that compared well with tower and aircraft data at a significantly lower cost. 21 refs., 1 fig., 2 tabs.

  18. Environmental applications of GPS

    SciTech Connect

    Vigil, S.A.; Zueck, D.

    1999-07-01

    The use of the Global Positioning System (GPS) has revolutionized air travel, ocean navigation, land navigation, and the collection of environmental data. Although a basic civilian GPS receiver can be purchased for as little as $100, the receiver is only the tip of a 12 billion dollar iceberg. This paper will discuss the history and basic operation of the Global Positioning System, a satellite-based precision positioning and timing service developed and operated by the Department of Defense. It will also describe the accuracy limitations of the civil GPS service and how accuracy can be enhanced by the use of differential GPS (DGPS), using either the free National Differential GPS system, or commercial differential monitor stations. Finally, the paper will discuss the future accuracy upgrades of civil GPS as a result of recent federal policy decisions.

  19. GPS L5 software receiver development for high-accuracy applications

    NASA Astrophysics Data System (ADS)

    Mongredien, Cecile

    The GPS L5 signal, part of the effort to modernize GPS, was designed to increase performance for civilian users. In order to fully exploit the structural innovations brought by this signal, new receiver architectures are needed. This dissertation proposes novel acquisition and tracking algorithms that can maximize the L5 signal performance in terms of acquisition robustness, tracking sensitivity and measurement accuracy. A cascaded algorithm is shown to enable robust and direct acquisition of the signal. A coarse acquisition step that coherently combines the data and pilot channel is first used to acquire the PRN code delay. An intermediate 1-ms FLL-based tracking is then introduced to remove the residual Doppler error and a pilot-only fine acquisition step is implemented to simultaneously acquire the NH code delay and perform bit synchronization. Different data- and pilot-only constant bandwidth tracking strategies are investigated to assess their relative performance in terms of sensitivity and accuracy in the presence of white noise, oscillator phase noise and receiver dynamics. Results show that the L5 dataless channel can increase phase and frequency tracking sensitivity by approximately 5 dB in addition to increasing accuracy. The superiority of phase tracking is also demonstrated since, in addition to enabling navigation message decoding, it is also shown to provide greater accuracy and better sensitivity than frequency tracking. Code tracking accuracy is also shown to greatly benefit from the dataless channel through the use of long coherent integration times. Further measurement accuracy can be achieved through an innovative technique that coherently combines the data and pilot channel at the correlator level. Although shown to greatly benefit from the presence of a dataless channel, the constant bandwidth tracking is outperformed by the Kalman filter-based tracking in all areas investigated. The difference between the two tracking strategies is the most

  20. Assessing the role of GPs in Nordic health care systems.

    PubMed

    Quaye, Randolph K

    2016-05-01

    Purpose This paper examines the changing role of general practitioners (GPs) in Nordic countries of Sweden, Norway and Denmark. It aims to explore the "gate keeping" role of GPs in the face of current changes in the health care delivery systems in these countries. Design/methodology/approach Data were collected from existing literature, interviews with GPs, hospital specialists and representatives of Danish regions and Norwegian Medical Association. Findings The paper contends that in all these changes, the position of the GPs in the medical division of labor has been strengthened, and patients now have increased and broadened access to choice. Research limitations/implications Health care cost and high cancer mortality rates have forced Nordic countries of Sweden, Norway and Denmark to rethink their health care systems. Several attempts have been made to reduce health care cost through market reform and by strenghtening the position of GPs. The evidence suggests that in Norway and Denmark, right incentives are in place to achieve this goal. Sweden is not far behind. The paper has limitations of a small sample size and an exclusive focus on GPs. Practical implications Anecdotal evidence suggests that physicians are becoming extremely unhappy. Understanding the changing status of primary care physicians will yield valuable information for assessing the effectiveness of Nordic health care delivery systems. Social implications This study has wider implications of how GPs see their role as potential gatekeepers in the Nordic health care systems. The role of GPs is changing as a result of recent health care reforms. Originality/value This paper contends that in Norway and Denmark, right incentives are in place to strengthen the position of GPs. PMID:27198702

  1. Crop Dusting Using GPS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Global Positioning System (GPS) receivers and GPS-based swath guidance systems are used on agricultural aircraft for remote sensing, airplane guidance, and to support variable-rate aerial application of crop inputs such as insecticides, cotton growth regulators, and defoliants. Agricultural aircraf...

  2. Radiation characterization report for the GPS Receiver microcontroller chip. Final report

    SciTech Connect

    Not Available

    1994-06-20

    The overall objective of this characterization test was to determine the sensitivity of the Motorola 68332 32-bit microcontroller to radiation induced single event upset and latch-up (SEU/SEL). The microcontroller is a key component of the GPS Receiver which will be a subsystem of the satellite required for the {open_quotes}FORTE{close_quotes} experiment. Testing was conducted at the Single Event Effects Laboratory at Brookhaven National Laboratory. The results obtained included a latch-up (SEL) threshold LET (Linear Energy Transfer) of 20 MeV-CM{sub 2}/mg and an upset (SEU) threshold LET of 5 MeV-CM{sup 2}/mg. The SEU threshold is typical of this technology, commercial 0.8{mu}m HCMOS. Some flow errors were observed that were not reset by the internal watchdog timer of the 68332. It is important that the Receiver design include a monitor of the device, such as an external watch-dog timer, that would initiate a reset of the program when this type of upset occurs. The SEL threshold is lower than would be expected for this 12{mu}m epi layer process and suggests the need for a strategy that would allow for a hard reset of the controller when a latch-up event occurs. Analysis of the galactic cosmic ray spectrum for the FORTE orbit was done and the results indicate a worst case latch-up rate for this device of 6.3 {times} 10{sup {minus}5} latch-ups per device day or roughly one latch-up per 43.5 device years.

  3. A statistical characterization of the Galileo-to-GPS inter-system bias

    NASA Astrophysics Data System (ADS)

    Gioia, Ciro; Borio, Daniele

    2016-06-01

    Global navigation satellite system operates using independent time scales and thus inter-system time offsets have to be determined to enable multi-constellation navigation solutions. GPS/Galileo inter-system bias and drift are evaluated here using different types of receivers: two mass market and two professional receivers. Moreover, three different approaches are considered for the inter-system bias determination: in the first one, the broadcast Galileo to GPS time offset is used to align GPS and Galileo time scales. In the second, the inter-system bias is included in the multi-constellation navigation solution and is estimated using the measurements available. Finally, an enhanced algorithm using constraints on the inter-system bias time evolution is proposed. The inter-system bias estimates obtained with the different approaches are analysed and their stability is experimentally evaluated using the Allan deviation. The impact of the inter-system bias on the position velocity time solution is also considered and the performance of the approaches analysed is evaluated in terms of standard deviation and mean errors for both horizontal and vertical components. From the experiments, it emerges that the inter-system bias is very stable and that the use of constraints, modelling the GPS/Galileo inter-system bias behaviour, significantly improves the performance of multi-constellation navigation.

  4. Positional accuracy of the Wide Area Augmentation System in consumer-grade GPS units

    NASA Astrophysics Data System (ADS)

    Arnold, Lisa L.; Zandbergen, Paul A.

    2011-07-01

    Global Positioning System devices are increasingly being used for data collection in many fields. Consumer-grade GPS units without differential correction have a published horizontal positional accuracy of approximately 10-15 m (average positional accuracy). An attractive option for differential correction for these GPS units is the Wide Area Augmentation System (WAAS). Most consumer-grade GPS units on the market are WAAS capable. According to the Federal Aviation Authority (FAA), the WAAS broadcast message provides integrity information about the GPS signal as well as accuracy improvements, which are reported to improve accuracy to 3-5 m. Limited empirical evidence has been published on the accuracy of WAAS-enabled GPS compared to autonomous GPS. An empirical study was conducted comparing the horizontal and vertical accuracy of WAAS-corrected GPS and autonomous GPS under ideal conditions using consumer-grade receivers. Data were collected for 30-min time spans over accurately surveyed control points. Metrics of median, 68th and 95th percentile, Root Mean Squared Error (RMSE), and average positional accuracy in the horizontal and vertical dimensions were computed and statistically compared. No statistically significant difference was found between WAAS and autonomous position fixes when using two different consumer-grade units. When using WAAS, a third unit type exhibited a statistically significant improvement in positional accuracy. Analysis of data collected for a 27-h time span indicates that while WAAS is altering the estimated position of a point compared to an autonomous position estimate, WAAS augmentation actually appears to decrease the positional accuracy.

  5. GPS aiding of ocean current determination. [Global Positioning System

    NASA Technical Reports Server (NTRS)

    Mohan, S. N.

    1981-01-01

    The navigational accuracy of an oceangoing vessel using conventional GPS p-code data is examined. The GPS signal is transmitted over two carrier frequencies in the L-band at 1575.42 and 1227.6 MHz. Achievable navigational uncertainties of differenced positional estimates are presented as a function of the parameters of the problem, with particular attention given to the effect of sea-state, user equivalent range error, uncompensated antenna motion, varying delay intervals, and reduced data rate examined in the unaided mode. The unmodeled errors resulting from satellite ephemeris uncertainties are shown to be negligible for the GPS-NDS (Navigation Development) satellites. Requirements are met in relatively calm seas, but accuracy degradation by a factor of at least 2 must be anticipated in heavier sea states. The aided mode of operation is examined, and it is shown that requirements can be met by using an inertial measurement unit (IMU) to aid the GPS receiver operation. Since the use of an IMU would mean higher costs, direct Doppler from the GPS satellites is presented as a viable alternative.

  6. GPS-based tracking system for TOPEX orbit determination

    NASA Technical Reports Server (NTRS)

    Melbourne, W. G.

    1984-01-01

    A tracking system concept is discussed that is based on the utilization of the constellation of Navstar satellites in the Global Positioning System (GPS). The concept involves simultaneous and continuous metric tracking of the signals from all visible Navstar satellites by approximately six globally distributed ground terminals and by the TOPEX spacecraft at 1300-km altitude. Error studies indicate that this system could be capable of obtaining decimeter position accuracies and, most importantly, around 5 cm in the radial component which is key to exploiting the full accuracy potential of the altimetric measurements for ocean topography. Topics covered include: background of the GPS, the precision mode for utilization of the system, past JPL research for using the GPS in precision applications, the present tracking system concept for high accuracy satellite positioning, and results from a proof-of-concept demonstration.

  7. Error Analysis System for Spacecraft Navigation Using the Global Positioning System (GPS)

    NASA Technical Reports Server (NTRS)

    Truong, S. H.; Hart, R. C.; Hartman, K. R.; Tomcsik, T. L.; Searl, J. E.; Bernstein, A.

    1997-01-01

    The Flight Dynamics Division (FDD) at the National Aeronautics and Space Administration (NASA) Goddard Space Flight Center (GSFC) is currently developing improved space-navigation filtering algorithms to use the Global Positioning System (GPS) for autonomous real-time onboard orbit determination. In connection with a GPS technology demonstration on the Small Satellite Technology Initiative (SSTI)/Lewis spacecraft, FDD analysts and programmers have teamed with the GSFC Guidance, Navigation, and Control Branch to develop the GPS Enhanced Orbit Determination Experiment (GEODE) system. The GEODE system consists of a Kalman filter operating as a navigation tool for estimating the position, velocity, and additional states required to accurately navigate the orbiting Lewis spacecraft by using astrodynamic modeling and GPS measurements from the receiver. A parallel effort at the FDD is the development of a GPS Error Analysis System (GEAS) that will be used to analyze and improve navigation filtering algorithms during development phases and during in-flight calibration. For GEAS, the Kalman filter theory is extended to estimate the errors in position, velocity, and other error states of interest. The estimation of errors in physical variables at regular intervals will allow the time, cause, and effect of navigation system weaknesses to be identified. In addition, by modeling a sufficient set of navigation system errors, a system failure that causes an observed error anomaly can be traced and accounted for. The GEAS software is formulated using Object Oriented Design (OOD) techniques implemented in the C++ programming language on a Sun SPARC workstation. The Phase 1 of this effort is the development of a basic system to be used to evaluate navigation algorithms implemented in the GEODE system. This paper presents the GEAS mathematical methodology, systems and operations concepts, and software design and implementation. Results from the use of the basic system to evaluate

  8. Inter-system biases estimation in multi-GNSS relative positioning with GPS and Galileo

    NASA Astrophysics Data System (ADS)

    Deprez, Cecile; Warnant, Rene

    2016-04-01

    The recent increase in the number of Global Navigation Satellite Systems (GNSS) opens new perspectives in the field of high precision positioning. Particularly, the European Galileo program has experienced major progress in 2015 with the launch of 6 satellites belonging to the new Full Operational Capability (FOC) generation. Associated with the ongoing GPS modernization, many more frequencies and satellites are now available. Therefore, multi-GNSS relative positioning based on GPS and Galileo overlapping frequencies should entail better accuracy and reliability in position estimations. However, the differences between satellite systems induce inter-system biases (ISBs) inside the multi-GNSS equations of observation. Once these biases estimated and removed from the model, a solution involving a unique pivot satellite for the two considered constellations can be obtained. Such an approach implies that the addition of even one single Galileo satellite to the GPS-only model will strengthen it. The combined use of L1 and L5 from GPS with E1 and E5a from Galileo in zero baseline double differences (ZB DD) based on a unique pivot satellite is employed to resolve ISBs. This model removes all the satellite- and receiver-dependant error sources by differentiating and the zero baseline configuration allows atmospheric and multipath effects elimination. An analysis of the long-term stability of ISBs is conducted on various pairs of receivers over large time spans. The possible influence of temperature variations inside the receivers over ISB values is also investigated. Our study is based on the 5 multi-GNSS receivers (2 Septentrio PolaRx4, 1 Septentrio PolaRxS and 2 Trimble NetR9) installed on the roof of our building in Liege. The estimated ISBs are then used as corrections in the multi-GNSS observation model and the resulting accuracy of multi-GNSS positioning is compared to GPS and Galileo standalone solutions.

  9. Single-frequency, dual-GNSS versus dual-frequency, single-GNSS: a low-cost and high-grade receivers GPS-BDS RTK analysis

    NASA Astrophysics Data System (ADS)

    Odolinski, Robert; Teunissen, Peter J. G.

    2016-06-01

    The concept of single-frequency, dual-system (SF-DS) real-time kinematic (RTK) positioning has become feasible since, for instance, the Chinese BeiDou Navigation Satellite System (BDS) has become operational in the Asia-Pacific region. The goal of the present contribution is to investigate the single-epoch RTK performance of such a dual-system and compare it to a dual-frequency, single-system (DF-SS). As the SF-DS we investigate the L1 GPS + B1 BDS model, and for DF-SS we take L1, L2 GPS and B1, B2 BDS, respectively. Two different locations in the Asia-Pacific region are analysed with varying visibility of the BDS constellation, namely Perth in Australia and Dunedin in New Zealand. To emphasize the benefits of such a model we also look into using low-cost ublox single-frequency receivers and compare such SF-DS RTK performance to that of a DF-SS, based on much more expensive survey-grade receivers. In this contribution a formal and empirical analysis is given. It will be shown that with the SF-DS higher elevation cut-off angles than the conventional 10° or 15° can be used. The experiment with low-cost receivers for the SF-DS reveals (for the first time) that it has the potential to achieve comparable ambiguity resolution performance to that of a DF-SS (L1, L2 GPS), based on the survey-grade receivers.

  10. Applications of a hand-held GPS receiver in South American rain forests

    NASA Technical Reports Server (NTRS)

    Baksh, Michael

    1991-01-01

    A hand-held Global Positioning System receiver was used to determine the precise locations of villages, houses, gardens, and other cultural and environmental features in poorly mapped South American rain forests. The Magellan NAV 1000 unit profides extremely accurate latitude and longitude information, but determination of altitude is problematical. Overall, the receiver effectively allows anthropologists to obtain essential locational data useful for categorizing land uses, mapping tribal boundaries, and other applications in regions where environmental conditions are harsh and/or accessibility is difficult.

  11. GPS water level measurements for Indonesia's Tsunami Early Warning System

    NASA Astrophysics Data System (ADS)

    Schöne, T.; Pandoe, W.; Mudita, I.; Roemer, S.; Illigner, J.; Zech, C.; Galas, R.

    2011-03-01

    On Boxing Day 2004, a severe tsunami was generated by a strong earthquake in Northern Sumatra causing a large number of casualties. At this time, neither an offshore buoy network was in place to measure tsunami waves, nor a system to disseminate tsunami warnings to local governmental entities. Since then, buoys have been developed by Indonesia and Germany, complemented by NOAA's Deep-ocean Assessment and Reporting of Tsunamis (DART) buoys, and have been moored offshore Sumatra and Java. The suite of sensors for offshore tsunami detection in Indonesia has been advanced by adding GPS technology for water level measurements. The usage of GPS buoys in tsunami warning systems is a relatively new approach. The concept of the German Indonesian Tsunami Early Warning System (GITEWS) (Rudloff et al., 2009) combines GPS technology and ocean bottom pressure (OBP) measurements. Especially for near-field installations where the seismic noise may deteriorate the OBP data, GPS-derived sea level heights provide additional information. The GPS buoy technology is precise enough to detect medium to large tsunamis of amplitudes larger than 10 cm. The analysis presented here suggests that for about 68% of the time, tsunamis larger than 5 cm may be detectable.

  12. Investigation of GPS/IMU Positioning System for Mining Equipment

    SciTech Connect

    Ken L. Stratton

    2006-09-13

    The objective of this project is to investigate the applicability of a combined Global Positioning System and Inertial Measurement Unit (GPS/IMU) for information based displays on earthmoving machines and for automated earthmoving machines in the future. This technology has the potential of allowing an information-based product like Caterpillar's Computer Aided Earthmoving System (CAES) to operate in areas with satellite shading. Satellite shading is an issue in open pit mining because machines are routinely required to operate close to high walls, which reduces significantly the amount of the visible sky to the GPS antenna mounted on the machine. An inertial measurement unit is a product, which provides data for the calculation of position based on sensing accelerations and rotation rates of the machine's rigid body. When this information is coupled with GPS it results in a positioning system that can maintain positioning capability during time periods of shading.

  13. Efficient detection and signal parameter estimation with application to high dynamic GPS receiver

    NASA Technical Reports Server (NTRS)

    Kumar, Rajendra (Inventor)

    1990-01-01

    In a system for deriving position, velocity, and acceleration information from a received signal emitted from an object to be tracked wherein the signal comprises a carrier signal phase modulated by unknown binary data and experiencing very high Doppler and Doppler rate, this invention provides combined estimation/detection apparatus for simultaneously detecting data bits and obtaining estimates of signal parameters such as carrier phase and frequency related to receiver dynamics in a sequential manner. There is a first stage for obtaining estimates of the signal parameters related to phase and frequency in the vicinity of possible data transitions on the basis of measurements obtained within a current data bit. A second stage uses the estimates from the first stage to decide whether or not a data transition has actually occurred. There is a third stage for removing data modulation from the received signal when a data transition has occurred and a fourth stage for using the received signal with data modulation removed therefrom to update global parameters which are dependent only upon receiver dynamics and independent of data modulation. Finally, there is a fifth stage for using the global parameters to determine the position, velocity, and acceleration of the object.

  14. Results of an Internet-Based Dual-Frequency Global Differential GPS System

    NASA Technical Reports Server (NTRS)

    Muellerschoen, R.; Bertiger, W.; Lough, M.

    2000-01-01

    Observables from a global network of 18 GPS receivers are returned in real-time to JPL over the open Internet. 30 - 40 cm RSS global GPS orbits and precise dual-frequency GPS clocks are computed in real-time with JPL's Real Time Gipsy (RTG) software.

  15. International GPS (Global Positioning System) Service for Geodynamics

    NASA Technical Reports Server (NTRS)

    Zumberge, J. F. (Editor); Liu, R. (Editor); Neilan, R. E. (Editor)

    1995-01-01

    The International GPS (Global Positioning System) Service for Geodynamics (IGS) began formal operation on January 1, 1994. This first annual report is divided into sections, which mirror different aspects of the service. Section (1) contains general information, including the history of the IGS, its organization, and the global network of GPS tracking sites; (2) contains information on the Central Bureau Information System; (3) describes the International Earth Rotation Service (IERS); (4) details collecting and distributing IGS data in Data Center reports; (6) describes how the IGS Analysis Centers generate their products; (7) contains miscellaneous contributions from other organizations that share common interests with the IGS.

  16. High accuracy autonomous navigation using the global positioning system (GPS)

    NASA Technical Reports Server (NTRS)

    Truong, Son H.; Hart, Roger C.; Shoan, Wendy C.; Wood, Terri; Long, Anne C.; Oza, Dipak H.; Lee, Taesul

    1997-01-01

    The application of global positioning system (GPS) technology to the improvement of the accuracy and economy of spacecraft navigation, is reported. High-accuracy autonomous navigation algorithms are currently being qualified in conjunction with the GPS attitude determination flyer (GADFLY) experiment for the small satellite technology initiative Lewis spacecraft. Preflight performance assessments indicated that these algorithms are able to provide a real time total position accuracy of better than 10 m and a velocity accuracy of better than 0.01 m/s, with selective availability at typical levels. It is expected that the position accuracy will be increased to 2 m if corrections are provided by the GPS wide area augmentation system.

  17. Development of Soil Compaction Analysis Software (SCAN) Integrating a Low Cost GPS Receiver and Compactometer

    PubMed Central

    Hwang, Jinsang; Yun, Hongsik; Kim, Juhyong; Suh, Yongcheol; Hong, Sungnam; Lee, Dongha

    2012-01-01

    A software for soil compaction analysis (SCAN) has been developed for evaluating the compaction states using the data from the GPS as well as a compactometer attached on the roller. The SCAN is distinguished from other previous software for intelligent compaction (IC) in that it can use the results from various types of GPS positioning methods, and it also has an optimal structure for remotely managing the large amounts of data gathered from numerous rollers. For this, several methods were developed: (1) improving the accuracy of low cost GPS receiver’s positioning results; (2) modeling the trajectory of a moving roller using a GPS receiver’s results and linking it with the data from the compactometer; and (3) extracting the information regarding the compaction states of the ground from the modeled trajectory, using spatial analysis methods. The SCAN was verified throughout various field compaction tests, and it has been confirmed that it can be a very effective tool in evaluating field compaction states. PMID:22736955

  18. Towards the Implementation of GPS-based Tsunami Early Warning System Using Ionospheric Measurements

    NASA Astrophysics Data System (ADS)

    Yang, Y. M.; Komjathy, A.; Meng, X.; Verkhoglyadova, O. P.; Mannucci, A. J.

    2014-12-01

    Natural hazards and solid Earth events, such as earthquakes, tsunamis and volcanic eruptions are actual sources that may trigger acoustic and gravity waves resulting in traveling ionospheric disturbances (TIDs) in the upper atmosphere. Trans-ionospheric radio wave measurements sense the total electron content (TEC) along the signal propagation path. In this research, we introduce a novel GPS-based detection and estimation technique for remote sensing of atmospheric wave-induced TIDs including space weather phenomena induced by major natural hazard events, using TEC time series collected from worldwide ground-based dual-frequency GNSS receiver networks. We will demonstrate the ability of using ground-based dual-frequency GPS measures to detect and monitor tsunami wave propagations from previous great earthquake and tsunami events including: 2011 Tohoku and 2010 Chile earthquakes and tsunamis. Two major TIDs with different propagation speeds and wavelengths were identified through analysis of the GPS remote sensing observations. Dominant physical characteristics of atmospheric wave-induced TIDs are found to be associated with specific tsunami propagations and oceanic Rayleigh waves. We compared GPS-based observations, corresponding model simulations and other geophysical measurements. Our results lead to a better understanding of the tsunami-induced ionosphere responses. In addition, we investigate ionospheric signatures caused by the 1964 Great Alaska Earthquake and tsunami using the GPS-based method. Based on current distribution of Plate Boundary Observatory (PBO) GPS stations, the simulated results indicate that tsunami-induced TIDs may be detected about 60 minutes prior to tsunamis arriving at the US west coast. It is expected that this GPS-based technology becomes an integral part of future early-warning systems.

  19. Future Technologies for Earth Science with Spaceborne GPS

    NASA Technical Reports Server (NTRS)

    Yunck, T. P.; Meehan, T. K.; Srinivasan, J. M.; Young, L. E.

    1995-01-01

    Spaceborne Global Positioning System (GPS) receivers will one day make important contributions to atmospheric, ionospheric, and solid Earth science. A number of GPS microsatellite missions are already in preparation in several countries. These missions require GPS flight receivers with capabilities well beyond the needs of most space missions. Receiver and microsatellite future technology is discussed.

  20. Satellite emission radio interferometric earth surveying series - GPS geodetic system

    NASA Technical Reports Server (NTRS)

    Macdoran, P. F.

    1979-01-01

    A concept called SERIES (satellite emissions radio interferometric earth surveying) which makes use of GPS (global positioning system) radio transmissions without any satellite modifications, is described. Through the use of very long baseline interferometry (VLBI) and its calibration methods, 0.5 to 3 cm three dimensional baseline accuracy can be achieved over distances of 2 to 200 km respectively, with only 2 hours of on-site data acquisition. Attention is given to such areas as: the radio flux equivalent of GPS transmissions, synthesized delay precision, transmission and frequency subsystem requirements, tropospheric and ionospheric errors. Applications covered include geodesy and seismic tectonics.

  1. Design and implementation of a GPS-aided inertial navigation system for a helicopter UAV

    NASA Astrophysics Data System (ADS)

    Kastelan, David R.

    Helicopter unmanned aerial vehicles (UAVs) benefit from vertical takeoff and landing, hover, low-speed, and cruising flight capabilities. This versatility has the expense of nonlinear, unstable, and underactuated system dynamics. These challenges and numerous potential applications make the helicopter UAV an interesting testbed for nonlinear control. A platform for such development has been established in the Applied Nonlinear Controls Lab (ANCL). A miniature helicopter was augmented with a manual/autonomous takeover system and the ANCL Avionics. This payload contains a global positioning system (GPS) receiver, inertial sensors, and communications and computing hardware. Allan variance analysis of inertial sensor data enabled the derivation of a GPS-aided inertial navigation system that was implemented on the ANCL Avionics. This extended Kalman filter (EKF)-based algorithm estimates vehicle position, velocity, and attitude necessary for system identification tasks and control system feedback. Performance validation of this algorithm was demonstrated in simulation and in experimental ground and flight tests.

  2. Geodetic positioning of the Aerospace Electronics Research Lab (ERL) Osborne Time Transfer Receiver (TTR) using the GPS NAVSTAR Block I satellites

    NASA Astrophysics Data System (ADS)

    Liu, Anthony S.

    1990-05-01

    Aerospace has routinely processed the Osborne Time Transfer Receiver (TTR) data for the purpose of monitoring the performance of ground and GPS atomic clocks in near real-time with on-line residual displays and characterizing clock stability with Allan Variance calculations. Recently, Aerospace added the ability to estimate the TTR's location by differentially correcting the TTR's location in the WGS84 reference system. This new feature is exercised on a set of TTR clock phase data and Sub-meter accurate station location estimates of the TTR at the Aerospace Electronic Research Lab (ERL) are obtained.

  3. Geodetic positioning of the Aerospace Electronics Research Lab (ERL) Osborne Time Transfer Receiver (TTR) using the GPS NAVSTAR Block I satellites

    NASA Technical Reports Server (NTRS)

    Liu, Anthony S.

    1990-01-01

    Aerospace has routinely processed the Osborne Time Transfer Receiver (TTR) data for the purpose of monitoring the performance of ground and GPS atomic clocks in near real-time with on-line residual displays and characterizing clock stability with Allan Variance calculations. Recently, Aerospace added the ability to estimate the TTR's location by differentially correcting the TTR's location in the WGS84 reference system. This new feature is exercised on a set of TTR clock phase data and Sub-meter accurate station location estimates of the TTR at the Aerospace Electronic Research Lab (ERL) are obtained.

  4. A System to Produce Precise Global GPS Network Solutions for all Geodetic GPS Stations in the World

    NASA Astrophysics Data System (ADS)

    Blewitt, G.; Kreemer, C. W.

    2010-12-01

    We have developed an end-to-end system that automatically seeks and routinely retrieves geodetic GPS data from ~5000 stations (currently) around the globe, reduces the data into unique, daily global network solutions, and produces high precision time series for station coordinates ready for time-series analysis, geophysical modeling and interpretation. Moreover, “carrier range” data are produced for all stations, enabling epoch-by-epoch tracking of individual station motions by precise point positioning for investigation of sub-daily processes, such as post-seismic after-slip and ocean tidal loading. Solutions are computed in a global reference frame aligned to ITRF, and optionally in user-specified continental-scale reference frames that can filter out common-mode signals to enhance regional strain anomalies. We describe the elements of this system, the underlying signal processing theory, the products, operational statistics, and scientific applications of our system. The system is fundamentally based on precise point positioning using JPL's GIPSY OASIS II software, coupled with ambiguity resolution and a global network adjustment of ~300,000 parameters per day using our newly developed Ambizap3 software. The system is designed to easily and efficiently absorb stations that deliver data very late, by recycling prior computations in the network adjustment, such that the resulting network solution is identical to starting from scratch. Thus, it becomes possible to trawl continuously the Internet for late arriving data, or for newly discovered data, and seamlessly update all GPS station time series using the new information content. As new stations are added to the processing archive, automated e-mail requests are made to H.-G. Scherneck's server at Chalmers University to compute ocean loading coefficients used by the station motion model. Rinex file headers are parsed and compared with alias tables in order to infer the correct receiver type and antenna

  5. A Correlation method for detection short-period perturbations in the ionosphere, from a large network of GPS receivers.

    NASA Astrophysics Data System (ADS)

    Lee, S.; Garrison, J. L.; Haase, J.; Calais, E.

    2006-12-01

    A technique has been developed for detecting small, short period, traveling perturbations in the ionosphere and estimating their propagation speed and direction from ground-based GPS data. These perturbations can result from atmosphere-ionosphere coupling following an earthquake, tsunami, or large human induced disturbances, such as rocket launches or nuclear weapons tests. These disturbances are often, however, observed at times in which no such source can be identified. The correlation method increases the signal to noise ratio of small amplitude signals, allowing the detection of weaker disturbances. Time series of the Integral Electron Content (IEC), generated from many ground-based dual-frequency GPS receivers, are passed through a filter with a pass band of (typically) 3-10 minutes. Cross-correlations between every pair of IEC time-series, from the same GPS satellite, viewed at multiple ground stations, are used to test for the presence of a disturbance, and measure the propagation delay between the two sub-ionosphere points (SIP's) corresponding to each pair of receivers. A two-dimensional plane wave model is fit to the set of delay measurements from all of the time series having correlation powers above a threshold. A change of variables is shown to convert this model to a linear one, allowing the use of linear least squares estimation methods. The inversion of the linear model is found to be very fast, numerically, allowing it to be used to process large data sets efficiently. It could, thus, be applied autonomously to process large GPS datasets efficiently, for statistical studies of the occurrence of these disturbances. A technique is developed to remove the effects of the time-varying satellite motion and to reconstruct the waveform of the disturbance that would have been observed at a fixed station in the ionosphere. Several post-processing tests are derived to test the velocity estimate accuracy and validity. Two weeks of data, one in the summer (5

  6. Investigation and evaluation of shuttle/GPS navigation system

    NASA Technical Reports Server (NTRS)

    Nilsen, P. W.

    1977-01-01

    Iterative procedures were used to analyze the performance of two preliminary shuttle/GPS navigation system configurations: an early OFT experimental system and a more sophisticated system which consolidates several separate navigation functions thus permitting net cost savings from decreased shuttle avionics weight and power consumption, and from reduced ground data processing. The GPS system can provide on-orbit navigation accuracy an order of magnitude better than the baseline system, with very adequate link margins. The worst-case link margin is 4.3 dB. This link margin accounts for shuttle RF circuit losses which were minimized under the constraints of program schedule and environmental limitations. Implicit in the link analyses are the location trade-offs for preamplifiers and antennas.

  7. 75 FR 28318 - Eighty-Second Meeting: RTCA Special Committee 159: Global Positioning System (GPS)

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-05-20

    ... System (GPS) AGENCY: Federal Aviation Administration (FAA), DOT. ACTION: Notice of RTCA Special Committee 159 meeting: Global Positioning System (GPS). SUMMARY: The FAA is issuing this notice to advise the public of a meeting of RTCA Special Committee 159: Global Positioning System (GPS). DATES: The...

  8. 77 FR 56254 - 89th Meeting: RTCA Special Committee 159, Global Positioning Systems (GPS)

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-09-12

    ... Federal Aviation Administration 89th Meeting: RTCA Special Committee 159, Global Positioning Systems (GPS... Notice of RTCA Special Committee 159, RTCA Special Committee 159, Global Positioning Systems (GPS... Special Committee 159, Global Positioning Systems (GPS). DATES: The meeting will be held October 5,...

  9. 76 FR 33022 - Eighty-Sixth Meeting: RTCA Special Committee 159: Global Positioning System (GPS)

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-06-07

    ... 159 meeting: Global Positioning System (GPS). SUMMARY: The FAA is issuing this notice to advise the public of a meeting of RTCA Special Committee 159: Global Positioning System (GPS). DATES: The meeting... for a Special Committee 159: Global Positioning System (GPS) meeting. The agenda will...

  10. 75 FR 2581 - Eighty-First Meeting: RTCA Special Committee 159: Global Positioning System (GPS)

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-01-15

    ... 159 meeting: Global Positioning System (GPS). SUMMARY: The FAA is issuing this notice to advise the public of a meeting of RTCA Special Committee 159: Global Positioning System (GPS). DATES: The meeting... hereby given for a Special Committee 159: Global Positioning System (GPS) meeting. The agenda...

  11. 78 FR 13396 - 90th Meeting: RTCA Special Committee 159, Global Positioning Systems (GPS)

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-02-27

    ... Federal Aviation Administration 90th Meeting: RTCA Special Committee 159, Global Positioning Systems (GPS... Notice of RTCA Special Committee 159, RTCA Special Committee 159, Global Positioning Systems (GPS... Special Committee 159, Global Positioning Systems (GPS). DATES: The meeting will be held March 12-15,...

  12. 78 FR 57672 - 91st Meeting: RTCA Special Committee 159, Global Positioning Systems (GPS)

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-09-19

    ... Federal Aviation Administration 91st Meeting: RTCA Special Committee 159, Global Positioning Systems (GPS... Notice of RTCA Special Committee 159, RTCA Special Committee 159, Global Positioning Systems (GPS... Special Committee 159, Global Positioning Systems (GPS) DATES: The meeting will be held October 7-11,...

  13. 76 FR 27744 - Eighty-Fifth Meeting: RTCA Special Committee 159: Global Positioning System (GPS)

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-05-12

    ... 159 meeting: Global Positioning System (GPS). SUMMARY: The FAA is issuing this notice to advise the public of a meeting of RTCA Special Committee 159: Global Positioning System (GPS). DATES: The meeting...), notice is hereby given for a Special Committee 159: Global Positioning System (GPS) meeting. The...

  14. Detection of VHF lightning from GPS orbit

    SciTech Connect

    Suszcynsky, D. M.

    2003-01-01

    Satellite-based VHF' lightning detection is characterized at GPS orbit by using a VHF receiver system recently launched on the GPS SVN 54 satellite. Collected lightning triggers consist of Narrow Bipolar Events (80%) and strong negative return strokes (20%). The results are used to evaluate the performance of a future GPS-satellite-based VHF global lightning monitor.

  15. Millimeter-accuracy GPS landslide monitoring using Precise Point Positioning with Single Receiver Phase Ambiguity (PPP-SRPA) resolution: a case study in Puerto Rico

    NASA Astrophysics Data System (ADS)

    Wang, G. Q.

    2013-03-01

    Continuous Global Positioning System (GPS) monitoring is essential for establishing the rate and pattern of superficial movements of landslides. This study demonstrates a technique which uses a stand-alone GPS station to conduct millimeter-accuracy landslide monitoring. The Precise Point Positioning with Single Receiver Phase Ambiguity (PPP-SRPA) resolution employed by the GIPSY/OASIS software package (V6.1.2) was applied in this study. Two-years of continuous GPS data collected at a creeping landslide were used to evaluate the accuracy of the PPP-SRPA solutions. The criterion for accuracy was the root-mean-square (RMS) of residuals of the PPP-SRPA solutions with respect to "true" landslide displacements over the two-year period. RMS is often regarded as repeatability or precision in GPS literature. However, when contrasted with a known "true" position or displacement it could be termed RMS accuracy or simply accuracy. This study indicated that the PPP-SRPA resolution can provide an accuracy of 2 to 3 mm horizontally and 8 mm vertically for 24-hour sessions with few outliers (< 1%) in the Puerto Rico region. Horizontal accuracy below 5 mm can be stably achieved with 4-hour or longer sessions if avoiding the collection of data during extreme weather conditions. Vertical accuracy below 10 mm can be achieved with 8-hour or longer sessions. This study indicates that the PPP-SRPA resolution is competitive with the conventional carrier-phase double-difference network resolution for static (longer than 4 hours) landslide monitoring while maintaining many advantages. It is evident that the PPP-SRPA method would become an attractive alternative to the conventional carrier-phase double-difference method for landslide monitoring, notably in remote areas or developing countries.

  16. System architecture study of an orbital GPS user terminal

    NASA Technical Reports Server (NTRS)

    Martin, D. P.; Neily, C. M., Jr.

    1980-01-01

    The generic RF and applications processing requirements for a GPS orbital navigator are considered. A line of demarcation between dedicated analog hardware, and software/processor implementation, maximizing the latter is discussed. A modular approach to R/PA design which permits several varieties of receiver to be constructed from basic components is described. It is a basic conclusion that software signal processing of the output of the baseband correlator is the best choice of transition from analog to digital signal processing. High performance sets requiring multiple channels are developed from a generic design by replicating the RF processing segment, and modifying the applications software to provide enhanced state propagation and estimation.

  17. GPS Altimetry

    NASA Technical Reports Server (NTRS)

    Lichten, Stephen M.

    1999-01-01

    The advent of satellite altimetry has greatly improved our ability to observe global ocean circulation. However, the swath of a single, nadir-viewing satellite altimeter is only a few km and the track spacing is several hundred km to resolve the two-dimensional structure of ocean eddies. Our goal is to increase spatial and temporal coverage by monitoring Global Positioning System (GPS) signals reflected from the ocean. A constellation of spacecraft would each carry a GPS receiver capable of recording 8 reflections simultaneously. The reflections are well distributed in azimuth and elevation and can be tracked continuously while the satellite is in view, and another is then acquired, as illustrated below. The diagram depicts a new approach at altimetry measurements where ocean surface reflected GPS signals are simultaneously tracked and processed in a GPS flight receiver in space. The reflected GPS signals from the ocean must be compared precisely with the direct GPS signals in order to infer the characteristics of the ocean from the combined data set. Understanding the features and accuracy of GPS altimetry measurement is crucial to establishing its suitability for oceanography. Preliminary work has enabled us to theoretically model the signal output of the correlator for a variety of system parameters such as wind speed (sea roughness), receiver height, incidence angle, receiver range and Doppler filter bandwidth and antenna gain. Expected signal-to-noise ratio has been estimated from which we have inferred, to a first approximation, the basic receiver gain requirements for a space-based altimeter and the expected range raw error. In 1998, work on a different task led to the extraction of the first reflected GPS signal observed from a spaceborne receiver during the 1995 Space Transportation System-68 (STS-68) Shuttle Radar Laboratory-2 (SRL-2) high resolution synthetic aperture radar mission. Good comparisons with our signal models have been obtained. Having

  18. Embedded GPS solves the installation dilemma

    NASA Astrophysics Data System (ADS)

    Sturza, Mark A.; Richards, Charles C.

    The authors describe a proposed embedded GPS/INS (Global Positioning System/Inertial Navigation System) architecture. The architecture provides full Phase III (jammed) GPS performance and supports all GPS/inertial integration approaches. The GPS unique interfaces are minimized by taking advantage of existing INS interfaces. Single-point failures are minimized by use of a partitioned power supply. It is concluded that the embedded GPS receiver offers equal or better performance, increased reliability, and significantly reduced weight and volume when compared to a standalone Receiver 3A.

  19. Observed solar radio burst effects on GPS/Wide Area Augmentation System carrier-to-noise ratio

    NASA Astrophysics Data System (ADS)

    Cerruti, Alessandro P.; Kintner, Paul M.; Gary, Dale E.; Lanzerotti, Louis J.; de Paula, Eurico R.; Vo, Hien B.

    2006-10-01

    The first direct observations of Global Positioning System (GPS) L1 (1.57542 GHz) carrier-to-noise ratio degradation due to a solar radio burst are presented for an event that occurred on 7 September 2005. Concurrent carrier-to-noise ratio data from GPS satellites are available from receivers at Arecibo Observatory, Puerto Rico; San Juan, Puerto Rico; and also from Anderson, South Carolina, United States. The right-hand circularly polarized (RHCP) signals from this solar radio burst caused a corresponding decrease in the carrier-to-noise ratio of about 2.3 dB across all visible satellites. The maximum solar radio burst power associated with this event was 8700 solar flux units (1 SFU = 10-22 W/m2/Hz) RHCP at 1600 MHz. Direct observations of GPS semicodeless L2 carrier-to-noise ratio degradation from receivers in Brazil are also presented for a solar radio burst that occurred on 28 October 2003. The maximum degradation at GPS L1 was about 3.0 dB, and a degradation of 10.0 dB was observed on the semicodeless L2 signal. Scaling to historic solar radio burst records suggests that GPS L1 receivers could fail to produce a navigation solution and that semicodeless L1/L2 receivers will fail.

  20. The GPS Space Service Volume

    NASA Technical Reports Server (NTRS)

    Bauer, F. H.; Moreau, M. C.; Dahle-Melsaether, M. E.; Petrofski, W. P.; Stanton, B. J.; Thomason, S.; Harris, G. A.; Sena, R. P.; Temple, L. Parker, III

    2006-01-01

    Prior to the advent of artificial satellites, the concept of navigating in space and the desire to understand and validate the laws of planetary and satellite motion dates back centuries. At the initiation of orbital flight in 1957, space navigation was dominated by inertial and groundbased tracking methods, underpinned by the laws of planetary motion. It was early in the 1980s that GPS was first explored as a system useful for refining the position, velocity, and timing (PVT) of other spacecraft equipped with GPS receivers. As a result, an entirely new GPS utility was developed beyond its original purpose of providing PVT services for land, maritime, and air applications. Spacecraft both above and below the GPS constellation now receive the GPS signals, including the signals that spill over the limb of the Earth. The use of radionavigation satellite services for space navigation in High Earth Orbits is in fact a capability unique to GPS. Support to GPS space applications is being studied and planned as an important improvement to GPS. This paper discusses the formalization of PVT services in space as part of an overall GPS improvement effort. It describes the GPS Space Service Volume (SSV) and compares it to the Terrestrial Service Volume (TSV). It also discusses SSV coverage with the current GPS constellation, coverage characteristics as a function of altitude, expected power levels, and coverage figures of merit.

  1. The UNAVCO Real-time GPS Data Processing System and Community Reference Data Sets

    NASA Astrophysics Data System (ADS)

    Sievers, C.; Mencin, D.; Berglund, H. T.; Blume, F.; Meertens, C. M.; Mattioli, G. S.

    2013-12-01

    UNAVCO has constructed a real-time GPS (RT-GPS) network of 420 GPS stations. The majority of the streaming stations come from the EarthScope Plate Boundary Observatory (PBO) through an NSF-ARRA funded Cascadia Upgrade Initiative that upgraded 100 backbone stations throughout the PBO footprint and 282 stations focused in the Pacific Northwest. Additional contributions from NOAA (~30 stations in Southern California) and the USGS (8 stations at Yellowstone) account for the other real-time stations. Based on community based outcomes of a workshop focused on real-time GPS position data products and formats hosted by UNAVCO in Spring of 2011, UNAVCO now provides real-time PPP positions for all 420 stations using Trimble's PIVOT software and for 50 stations using TrackRT at the volcanic centers located at Yellowstone (Figure 1 shows an example ensemble of TrackRT networks used in processing the Yellowstone data), Mt St Helens, and Montserrat. The UNAVCO real-time system has the potential to enhance our understanding of earthquakes, seismic wave propagation, volcanic eruptions, magmatic intrusions, movement of ice, landslides, and the dynamics of the atmosphere. Beyond its increasing uses for science and engineering, RT-GPS has the potential to provide early warning of hazards to emergency managers, utilities, other infrastructure managers, first responders and others. With the goal of characterizing stability and improving software and higher level products based on real-time GPS time series, UNAVCO is developing an open community standard data set where data processors can provide solutions based on common sets of RT-GPS data which simulate real world scenarios and events. UNAVCO is generating standard data sets for playback that include not only real and synthetic events but also background noise, antenna movement (e.g., steps, linear trends, sine waves, and realistic earthquake-like motions), receiver drop out and online return, interruption of communications (such as

  2. The Utility and Validity of Kinematic GPS Positioning for the Geosar Airborne Terrain Mapping Radar System

    NASA Technical Reports Server (NTRS)

    Freedman, Adam; Hensley, Scott; Chapin, Elaine; Kroger, Peter; Hussain, Mushtaq; Allred, Bruce

    1999-01-01

    GeoSAR is an airborne, interferometric Synthetic Aperture Radar (IFSAR) system for terrain mapping, currently under development by a consortium including NASA's Jet Propulsion Laboratory (JPL), Calgis, Inc., a California mapping sciences company, and the California Department of Conservation (CaIDOC), with funding provided by the U.S. Army Corps of Engineers Topographic Engineering Center (TEC) and the U.S. Defense Advanced Research Projects Agency (DARPA). IFSAR data processing requires high-accuracy platform position and attitude knowledge. On 9 GeoSAR, these are provided by one or two Honeywell Embedded GPS Inertial Navigation Units (EGI) and an Ashtech Z12 GPS receiver. The EGIs provide real-time high-accuracy attitude and moderate-accuracy position data, while the Ashtech data, post-processed differentially with data from a nearby ground station using Ashtech PNAV software, provide high-accuracy differential GPS positions. These data are optimally combined using a Kalman filter within the GeoSAR motion measurement software, and the resultant position and orientation information are used to process the dual frequency (X-band and P-band) radar data to generate high-accuracy, high -resolution terrain imagery and digital elevation models (DEMs). GeoSAR requirements specify sub-meter level planimetric and vertical accuracies for the resultant DEMS. To achieve this, platform positioning errors well below one meter are needed. The goal of GeoSAR is to obtain 25 cm or better 3-D positions from the GPS systems on board the aircraft. By imaging a set of known point target corner-cube reflectors, the GeoSAR system can be calibrated. This calibration process yields the true position of the aircraft with an uncertainty of 20- 50 cm. This process thus allows an independent assessment of the accuracy of our GPS-based positioning systems. We will present an overview of the GeoSAR motion measurement system, focusing on the use of GPS and the blending of position data from the

  3. Dual-band RF receiver for GPS-L1 and compass-B1 in a 55-nm CMOS

    NASA Astrophysics Data System (ADS)

    Songting, Li; Jiancheng, Li; Xiaochen, Gu; Zhaowen, Zhuang

    2014-02-01

    A fully integrated dual-band RF receiver with a low-IF architecture is designed and implemented for GPS-L1 and Compass-B1 in a 55-nm CMOS process. The receiver incorporates two independent IF channels with 2 or 4 MHz bandwidth to receive dual-band signals around 1.57 GHz respectively. By implementing a flexible frequency plan, the RF front-end and frequency synthesizer are shared for the dual-band operation to save power consumption and chip area, as well as avoiding LO crosstalk. A digital automatic gain control (AGC) loop is utilized to improve the receiver's robustness by optimizing the conversion gain of the analog-to-digital converter (ADC). While drawing about 20 mA per channel from a 1.2 V supply, this RF receiver achieves a minimum noise figure (NF) of about 1.8 dB, an image rejection (IMR) of more than 35 dB, a maximum voltage gain of about 122 dB, a gain dynamic range of 82 dB, and an maximum input-referred 1 dB compression point of about -36.5 dBm with an active die area of 1.5 × 1.4 mm2 for the whole chip.

  4. The International GPS Service (IGS) as a Continuous Reference System for Precise GPS Positioning

    NASA Technical Reports Server (NTRS)

    Neilan, Ruth; Heflin, Michael; Watkins, Michael; Zumberge, James

    1996-01-01

    The International GPS Service for Geodynamics (IGS) is an organization which operates under the auspices of the International Association of Geodesy (IAG) and has been operational since January 1994. The primary objective of the IGS is to provide precise GPS data and data products to support geodetic and geophysical research activities.

  5. A GPS-based Real-time Road Traffic Monitoring System

    NASA Astrophysics Data System (ADS)

    Tanti, Kamal Kumar

    In recent years, monitoring systems are astonishingly inclined towards ever more automatic; reliably interconnected, distributed and autonomous operation. Specifically, the measurement, logging, data processing and interpretation activities may be carried out by separate units at different locations in near real-time. The recent evolution of mobile communication devices and communication technologies has fostered a growing interest in the GIS & GPS-based location-aware systems and services. This paper describes a real-time road traffic monitoring system based on integrated mobile field devices (GPS/GSM/IOs) working in tandem with advanced GIS-based application software providing on-the-fly authentications for real-time monitoring and security enhancement. The described system is developed as a fully automated, continuous, real-time monitoring system that employs GPS sensors and Ethernet and/or serial port communication techniques are used to transfer data between GPS receivers at target points and a central processing computer. The data can be processed locally or remotely based on the requirements of client’s satisfaction. Due to the modular architecture of the system, other sensor types may be supported with minimal effort. Data on the distributed network & measurements are transmitted via cellular SIM cards to a Control Unit, which provides for post-processing and network management. The Control Unit may be remotely accessed via an Internet connection. The new system will not only provide more consistent data about the road traffic conditions but also will provide methods for integrating with other Intelligent Transportation Systems (ITS). For communication between the mobile device and central monitoring service GSM technology is used. The resulting system is characterized by autonomy, reliability and a high degree of automation.

  6. Differential GPS and system integration of the Low Visibility Landing and Surface Operations (LVLASO) demonstration

    NASA Technical Reports Server (NTRS)

    Rankin, James M.

    1994-01-01

    The LVLASO Flight Demonstration of ASTA concepts (FDAC) integrates NASA-Langley's electronic moving map display and Transport Systems Research Vehicle (TSRV) (a modified Boeing 737 aircraft); ARINC's VHF data link, GPS ground station, and automated controller workstation; and Norden's surface radar/airport movement safety system. Aircraft location is shown on the electronic map display in the cockpit. An approved taxi route as well as other aircraft and surface traffic are also displayed. An Ashtech Z12 Global Positioning System (GPS) receiver on the TSRV estimates the aircraft's position. In Differential mode (DSPS), the Ashtech receiver accepts differential C/A code pseudorange corrections from a GPS ground station. The GPS ground station provides corrections up to ten satellites. The corrections are transmitted on a VHF data link at a 1 Hz. rate using the RTCM-104 format. DGPS position estimates will be within 5 meters of actual aircraft position. DGPS position estimates are blended with position, velocity, acceleration, and heading data from the TSRV Air Data/Inertial Reference System (ADIRS). The ADIRS data is accurate in the short-term, but drifts over time. The DGPS data is used to keep the ADIRS position accurate. Ownship position, velocity, heading, and turn rate are sent at a 20 Hz. rate to the electronic map display. Airport traffic is detected by the airport surface radar system. Aircraft and vehicles such as fuel trucks and baggage carts are detected. The traffic's location, velocity, and heading are sent to the TSRV. To prevent traffic symbology from jumping each second when a location update arrives, velocity and heading are used to predict a new traffic location for each display update. Possible runway incursions and collisions can be shown on the electronic map. Integrating the different systems used in the FDAC requires attention to the underlying coordinate systems. The airport diagram displayed on the electronic map is obtained from published

  7. The impact of Sep 30 - Oct 1, 2012 geomagnetic storm on the Ionosphere studied using GPS receivers in Uganda

    NASA Astrophysics Data System (ADS)

    Mungufeni, Patrick

    We have used VTEC and S4 indices obtained from the GPS receivers, namely: GPS-SCINDA at Mbarara and Kampala, UNAVCO station at Entebbe to show TEC variability, occurrence of ionospheric irregularities and scintillations during the intense geomagnetic storm of Sep 30 - Oct 1, 2012. TEC response to the storm showed a positive storm effect a few hours after the SSC followed by a negative storm effect and then a long period of positive storm effect during the recovery phase of the storm. The peak of the positive storm effect reached 120.7 % at 21:00 LT (30 hours after the SSC). Primarily, these variations are connected with transport by electric fields and neutral winds, changes in the neutral composition and structure. The storm significantly reduced TEC depletion and suppressed irregularities due to reduction of day time eastward electric field by the ring current. Post mid-night scintillation activity at about 09:00 LT reached almost saturation level. Trans-ionospheric communication, navigation, and surveillance signals could be affected by such modified ionosphere.

  8. Development of a GPS buoy system for monitoring tsunami, sea waves, ocean bottom crustal deformation and atmospheric water vapor

    NASA Astrophysics Data System (ADS)

    Kato, Teruyuki; Terada, Yukihiro; Nagai, Toshihiko; Koshimura, Shun'ichi

    2010-05-01

    We have developed a GPS buoy system for monitoring tsunami for over 12 years. The idea was that a buoy equipped with a GPS antenna and placed offshore may be an effective way of monitoring tsunami before its arrival to the coast and to give warning to the coastal residents. The key technology for the system is real-time kinematic (RTK) GPS technology. We have successfully developed the system; we have detected tsunamis of about 10cm in height for three large earthquakes, namely, the 23 June 2001 Peru earthquake (Mw8.4), the 26 September 2003 Tokachi earthquake (Mw8.3) and the 5 September 2004 earthquake (Mw7.4). The developed GPS buoy system is also capable of monitoring sea waves that are mainly caused by winds. Only the difference between tsunami and sea waves is their frequency range and can be segregated each other by a simple filtering technique. Given the success of GPS buoy experiments, the system has been adopted as a part of the Nationwide Ocean Wave information system for Port and HArborS (NOWPHAS) by the Ministry of Land, Infrastructure, Transport and Tourism of Japan. They have established more than eight GPS buoys along the Japanese coasts and the system has been operated by the Port and Airport Research Institute. As a future scope, we are now planning to implement some other additional facilities for the GPS buoy system. The first application is a so-called GPS/Acoustic system for monitoring ocean bottom crustal deformation. The system requires acoustic waves to detect ocean bottom reference position, which is the geometrical center of an array of transponders, by measuring distances between a position at the sea surface (vessel) and ocean bottom equipments to return the received sonic wave. The position of the vessel is measured using GPS. The system was first proposed by a research group at the Scripps Institution of Oceanography in early 1980's. The system was extensively developed by Japanese researchers and is now capable of detecting ocean

  9. Multi buoy system observation for GPS/A seafloor positioning

    NASA Astrophysics Data System (ADS)

    Mukaiyama, H.; Ikuta, R.; Tadokoro, K.; Yasuda, K.; Watanabe, T.; Chiba, H.; Sayanagi, K.

    2014-12-01

    We are developing a method for observation of seafloor crustal deformation using kinematic GPS and acoustic ranging system. The system measures seafloor crustal deformation by determining position of benchmarks on the seafloor using a vessel which link-up GPS and acoustic signals. Acoustic ranging is used to measure distance between the vessel and the seafloor benchmarks. And kinematic GPS is used to locate the moving vessel every 0.2 seconds. Now we have deployed 4 seafloor benchmark units at Suruga Bay and 4 units at Kumano Basin both off-pacific coast Japan. At each survey site, three seafloor transponders are settled to define a benchmark unit. In this system, each measurement takes about ten hours and both sound speed structure and the benchmark unit positions were determined simultaneously for the each measurement using a tomographic technique. This tomographic technique was adopted based on assumption that the sound speed structure is horizontally layered and changes only in time, not in space. However, when sound speed structure has a heterogeneity, the assumption of a horizontal layering causes systematic error in the determination of seafloor benchmarks(Ikuta et al 2009AGU). So we are developing a new system using multi-buoy. Multi-buoy plays the role of vessel. Conducting observation using the buoys, we can estimate spatial variation of sound speed structures as a sloped structure every moment. With the single vessel system, we solve a kind of average sound speed over the different paths to the three seafloor transponders. Using the multi-buoy system, they can detect the lateral variation as difference of the average sound speeds obtained by different buoys, which improve the accuracy of the benchmark locations. In November 2013, Observation of seafloor crustal deformation using the buoys was held in Suruga Bay. In this study, we report the result of estimations of heterogeneous sound speed structures.

  10. Differences between GPS receiver antenna calibration models and influence on geodetic positioning

    NASA Astrophysics Data System (ADS)

    Baire, Q.; Bruyninx, C.; Pottiaux, E.; Legrand, J.; Aerts, W.

    2012-12-01

    Since April 2011, the igs08.atx antenna calibration model is used in the routine IGS (International GNSS Service) data analysis. The model includes mean robot calibrations to correct for the offset and phase center variations of the GNSS receiver antennas. These so-called "type" calibrations are means of the individual calibrations available for a specific antenna/radome combination. The aim of this study is to quantify the offset on the computed station positions when using different receiver antenna calibration models in the analysis. First, type calibrations are compared to individual receiver antenna calibrations. We analyze the observations of the 43 EUREF Permanent Network (EPN) stations equipped with individually calibrated receiver antenna over the period covering 2003 to 2010 using the Precise Point Positioning (PPP) technique. The difference between individual and type calibrations has a larger impact on the vertical component: the position offsets reach 4 mm in the horizontal components and 10 mm in the vertical component. In a second step, the effect of different individual calibration models of the same antenna on the positioning is assessed. For that purpose, data from several GNSS stations equipped with an antenna which has been individually calibrated at two calibration agencies are used. Those agencies are GEO++, performing robot calibrations, and University of Bonn, performing anechoic chamber calibrations, both recognized by the IGS. Initial results show that the position offsets induced by different calibration methods can reach 3 mm in the horizontal components and 7 mm in the vertical component.

  11. A Micromechanical INS/GPS System for Small Satellites

    NASA Technical Reports Server (NTRS)

    Barbour, N.; Brand, T.; Haley, R.; Socha, M.; Stoll, J.; Ward, P.; Weinberg, M.

    1995-01-01

    The cost and complexity of large satellite space missions continue to escalate. To reduce costs, more attention is being directed toward small lightweight satellites where future demand is expected to grow dramatically. Specifically, micromechanical inertial systems and microstrip global positioning system (GPS) antennas incorporating flip-chip bonding, application specific integrated circuits (ASIC) and MCM technologies will be required. Traditional microsatellite pointing systems do not employ active control. Many systems allow the satellite to point coarsely using gravity gradient, then attempt to maintain the image on the focal plane with fast-steering mirrors. Draper's approach is to actively control the line of sight pointing by utilizing on-board attitude determination with micromechanical inertial sensors and reaction wheel control actuators. Draper has developed commercial and tactical-grade micromechanical inertial sensors, The small size, low weight, and low cost of these gyroscopes and accelerometers enable systems previously impractical because of size and cost. Evolving micromechanical inertial sensors can be applied to closed-loop, active control of small satellites for micro-radian precision-pointing missions. An inertial reference feedback control loop can be used to determine attitude and line of sight jitter to provide error information to the controller for correction. At low frequencies, the error signal is provided by GPS. At higher frequencies, feedback is provided by the micromechanical gyros. This blending of sensors provides wide-band sensing from dc to operational frequencies. First order simulation has shown that the performance of existing micromechanical gyros, with integrated GPS, is feasible for a pointing mission of 10 micro-radians of jitter stability and approximately 1 milli-radian absolute error, for a satellite with 1 meter antenna separation. Improved performance micromechanical sensors currently under development will be

  12. Development of Space Weather Monitoring System and Statistical Study of GPS Scintillations

    NASA Astrophysics Data System (ADS)

    Zachariah, T. P.; Isaac, R.; Kim, L.; Rios, N.

    2012-12-01

    Autonomous Adaptive Low-Power Instrument Platforms (AAL-PIP), containing several space weather instruments, were recently deployed in Antarctica. Among the instrumentation on the platforms are magnetometers for measuring magnetic activity and Connected Autonomous Space Environment Sensor (CASES) Global Positioning System (GPS) software-defined receivers for measuring ionospheric scintillation, the diffraction of signal due to ionospheric irregularities. In order to adequately keep track of the measurement data and the platform, a remote user interface is necessary. In this project, we develop a Graphical User Interface (GUI) that displays daily magnetic activity and GPS scintillation events, as well as housekeeping data to monitor system health. Then, we conduct a statistical study to reveal a correlation between the disturbances in the ionosphere and GPS signal fading. In this study, we find general patterns of the relationship in the recorded data from 24 January 2012 through 7 May 2012 utilizing different sets of data from the AAL-PIP system and reputed solar storm indices.

  13. A precise GPS-based time and frequency system

    NASA Technical Reports Server (NTRS)

    Mcnabb, Jack; Fossler, Earl

    1993-01-01

    An approach to implementing a compact, highly reliable and precise Master Time and Frequency subsystem usable in a variety of applications is described. These applications include, among others, Satellite Ground Terminals, Range Timing Stations, Communications Terminals, and Power Station Timing subsystems. All time and frequency output signals are locked to Universal Time via the GPS Satellite system. The system provides for continued output of precise signals in the event of GPS signal interruption from antenna or lead-in breakage or other causes. Cost/performance tradeoffs affecting system accuracy over the short, medium, and long term are discussed. A unique approach to redundant system design provides an architecture with the reliability advantage of triple-redundant majority voting and the cost advantages of dual-redundant elements. The system can be configured to output a variety of precise time and frequency signals and the design can be tailored to output as few, or as many, types and quantities of signals as are required by the application.

  14. Continuous generation and two-dimensional structure of equatorial plasma bubbles observed by high-density GPS receivers in Southeast Asia

    NASA Astrophysics Data System (ADS)

    Buhari, S. M.; Abdullah, M.; Hasbi, A. M.; Otsuka, Y.; Yokoyama, T.; Nishioka, M.; Tsugawa, T.

    2014-12-01

    High-density GPS receivers located in Southeast Asia (SEA) were utilized to study the two-dimensional structure of ionospheric plasma irregularities in the equatorial region. The longitudinal and latitudinal variations of tens of kilometer-scale irregularities associated with equatorial plasma bubbles (EPBs) were investigated using two-dimensional maps of the rate of total electron content change index (ROTI) from 127 GPS receivers with an average spacing of about 50-100 km. The longitudinal variations of the two-dimensional maps of GPS ROTI measurement on 5 April 2011 revealed that 16 striations of EPBs were generated continuously around the passage of the solar terminator. The separation distance between the subsequent onset locations varied from 100 to 550 km with 10 min intervals. The lifetimes of the EPBs observed by GPS ROTI measurement were between 50 min and over 7 h. The EPBs propagated 440-3000 km toward the east with velocities of 83-162 m s-1. The longitudinal variations of EPBs by GPS ROTI keogram coincided with the depletions of 630 nm emission observed using the airglow imager. Six EPBs were observed by GPS ROTI along the meridian of Equatorial Atmosphere Radar (EAR), while only three EPBs were detected by the EAR. The high-density GPS receivers in SEA have an advantage of providing time continuous descriptions of latitudinal/longitudinal variations of EPBs with both high spatial resolution and broad geographical coverage. The spatial periodicity of the EPBs could be associated with a wavelength of the quasiperiodic structures on the bottomside of the F region which initiate the Rayleigh-Taylor instability.

  15. A Low Cost Automated Monitoring System for Landslides Using Dual Frequency GPS

    NASA Astrophysics Data System (ADS)

    Mills, H.; Edwards, S.

    2006-12-01

    Landslides are an existing and permanent threat to societies across the globe, generating financial and human losses whenever and wherever they occur. Drawing together the strands of science that provide increased understanding of landslide triggers through accurate modelling is therefore vital for the development of mitigation and management strategies. Together with climatic and geomorphological data a key input here is information on the precise location and timing of landslide events. However, the detailed monitoring of landslides and precursor movements is generally limited to episodic campaigns where limiting factors include equipment and mobilisation costs, time constraints and spatial resolution. This research has developed a geodetic tool of benefit to scientists involved in the development of closely coupled models that seek to explain trigger mechanisms such as rainfall duration and intensity and changes in groundwater pressure to actual real land movements. A fully automated low cost dual frequency GPS station for the continuous in-situ monitoring of landslide sites has been developed. System configuration combines a dual frequency GPS receiver, PC board with a GPRS modem and power supply to deliver 24hr/365day operation capability. Individual components have been chosen to provide the highest accuracies while minimising power consumption resulting in a system around half that of equivalent commercial systems. Measurement point-costs can be further reduced through the use of antenna switching and multi antenna arrays. Continuous data is delivered via mobile phone uplink and processed automatically using geodetic software. The developed system has been extensively tested on a purpose built platform capable of simulating ground movements. Co-mounted antennas have allowed direct comparisons with more expensive geodetic GPS receivers. The system is capable of delivering precise 3D coordinates with a 9 mm rms. The system can be up-scaled resulting in the

  16. Precise GPS orbits for geodesy

    NASA Technical Reports Server (NTRS)

    Colombo, Oscar L.

    1994-01-01

    The Global Positioning System (GPS) has become, in recent years, the main space-based system for surveying and navigation in many military, commercial, cadastral, mapping, and scientific applications. Better receivers, interferometric techniques (DGPS), and advances in post-processing methods have made possible to position fixed or moving receivers with sub-decimeter accuracies in a global reference frame. Improved methods for obtaining the orbits of the GPS satellites have played a major role in these achievements; this paper gives a personal view of the main developments in GPS orbit determination.

  17. Precise GPS orbits for geodesy

    NASA Astrophysics Data System (ADS)

    Colombo, Oscar L.

    1994-05-01

    The Global Positioning System (GPS) has become, in recent years, the main space-based system for surveying and navigation in many military, commercial, cadastral, mapping, and scientific applications. Better receivers, interferometric techniques (DGPS), and advances in post-processing methods have made possible to position fixed or moving receivers with sub-decimeter accuracies in a global reference frame. Improved methods for obtaining the orbits of the GPS satellites have played a major role in these achievements; this paper gives a personal view of the main developments in GPS orbit determination.

  18. A Canadian Pilot Project for a GPS-Augmented Tsunami Warning System

    NASA Astrophysics Data System (ADS)

    Dragert, H.; Schmidt, M.; Wang, K.; Bock, Y.

    2005-12-01

    Whether a tsunami has been generated from a large earthquake immediately offshore cannot be determined within a crucial time window from seismic or tide gauge data alone. Geological and geodetic data show that coseismic motions of the Earth's surface even hundreds of kilometers from the fault can be used to determine the nature of the rupture and whether the earthquake is tsunamigenic. High-rate (1 sps or greater), totally autonomous GPS stations located along the coast can provide on-line streamed data that can be analyzed in real time to provide an update of relative positions to an accuracy of 1-2 cm horizontally and 3-5 cm vertically with a latency of a few seconds. Regional ground displacements along the coast at the time of a major offshore earthquake could therefore point to the certainty of a tsunami within less than a minute. The Geological Survey of Canada is currently setting up a prototype network to facilitate real-time positioning along the coast of the Canadian segment of the Cascadia subduction zone. The aim is to evaluate the realizability and effectiveness of automatically determining major vertical and horizontal motion at coastal versus inland GPS stations that would unambiguously and rapidly indicate tsunami generation. A network of GPS receivers purchased by the Canadian Hydrographic Service is currently being deployed at geodetic quality installations with continuous on-line communications. As part of this system, we are implementing real-time GPS technology previously applied to seismic (Bock et al., 2004; Langbein and Bock, 2004; Yamagiwa et al., 2004) and volcanic (Mattia et al., 2004) monitoring applications. The target date to have a prototype system operating is December 2005. It is hoped that this relatively low cost technique can become a mainstream tool of tsunami warning systems worldwide.

  19. First Public Library Satellite Receiver System.

    ERIC Educational Resources Information Center

    Donaldson, Marion F.

    1982-01-01

    Description of video services at Lake County Public Library, Indiana, highlights the installation of a satellite receiver system and notes funding and justification, components of a satellite system, decisions and sources of assistance, programming available, and future considerations. (EJS)

  20. Evaluation of a Mobile Phone for Aircraft GPS Interference

    NASA Technical Reports Server (NTRS)

    Nguyen, Truong X.

    2004-01-01

    Measurements of spurious emissions from a mobile phone are conducted in a reverberation chamber for the Global Positioning System (GPS) radio frequency band. This phone model was previously determined to have caused interference to several aircraft GPS receivers. Interference path loss (IPL) factors are applied to the emission data, and the outcome compared against GPS receiver susceptibility. The resulting negative safety margins indicate there are risks to aircraft GPS systems. The maximum emission level from the phone is also shown to be comparable with some laptop computer's emissions, implying that laptop computers can provide similar risks to aircraft GPS receivers.

  1. Large-scale traveling ionospheric disturbances observed using GPS receivers over high-latitude and equatorial regions

    NASA Astrophysics Data System (ADS)

    Idrus, Intan Izafina; Abdullah, Mardina; Hasbi, Alina Marie; Husin, Asnawi; Yatim, Baharuddin

    2013-09-01

    This paper presents the first results of large-scale traveling ionospheric disturbances (LSTIDs) observation during two moderate magnetic storm events on 28 May 2011 (SYM-H∼ -94 nT and Dst∼-80 nT) and 6 August 2011 (SYM-H∼-126 nT and Dst∼-113 nT) over the high-latitude region in Russia, Sweden, Norway, Iceland and Greenland and equatorial region in the Peninsular Malaysia using vertical total electron content (VTEC) from the Global Positioning System (GPS) observations measurement. The propagation of the LSTID signatures in the GPS TEC measurements over Peninsular Malaysia was also investigated using VTEC map. The LSTIDs were found to propagate both equatorward and poleward directions during these two events. The results showed that the LSTIDs propagated faster at high-latitude region with an average phase velocity of 1074.91 m/s than Peninsular Malaysia with an average phase velocity of 604.84 m/s. The LSTIDs at the high-latitude region have average periods of 150 min whereas the ones observed over Peninsular Malaysia have average periods of 115 min. The occurrences of these LSTIDs were also found to be the subsequent effects of substorm activities in the auroral region. To our knowledge, this is the first result of observation of LSTIDs over Peninsular Malaysia during the 24th solar cycle.

  2. Kalman filtering for GPS/magnetometer integrated navigation system

    NASA Astrophysics Data System (ADS)

    Guo, Hang; Yu, Min; Zou, Chengwu; Huang, Wenwen

    2010-06-01

    This paper investigated the data processing method for a GPS/IMU/magnetometer integrated system with Kalman filtering (KF). As a result of GPS/IMU/magnetometer land vehicle system, dead-reckoning of magnetometer and accelerometer integrated subsystem bridged very well the GPS signal outage due to the trees on the two sides of the road. Both differential GPS data processing method and the carrier-phase method with magnetometers' outputs for predicting the car position, velocity, and acceleration (PVA) are presented. The results from DGPS with Kinematical Positioning (KINPOS) software shown that the averages of the north, east, and down direction standard deviation (short for "std") are 0.014, 0.010, and 0.018 m, respectively. The std of velocities and accelerations derived by the position and velocity differentiation are 10, 7, 13 mm/s, 7, 5, 9 mm/s 2, respectively. This method for getting velocities and accelerations requires higher accurate position coordinates. But the position accuracy has frequently been degraded in this case when the car drove under the trees or other similar kinematical environments. That caused the larger velocity and acceleration errors. While the results from the carrier-phase method are std of the velocities = 2.1 mm/s, 1.3 mm/s, 3.7 mm/s in north, east, down, and std of the accelerations = 1.5 mm/s 2, 0.9 mm/s 2, 2.3 mm/s 2 for the static test period; as compared with KINPOS software results, std of the velocity difference between the carrier-phase method and the DGPS method = 7 mm/s, 6.9 mm/s, 9.7 mm/s in north, east, down direction, and std of acceleration difference = 5.0 mm/s 2, 4.5 mm/s 2, 7.5 mm/s 2 in north, east, down direction for the kinematical test period. Obviously, errors come from both the carrier-phase method and DGPS velocity and acceleration results derived directly by the position differentiation. In addition, better accuracy of positions than that before KF has been got by means of velocities and accelerations derived

  3. GPS PWV Information System of the Decision Making Support System Prototype for Typhoon-Flood Disaster

    NASA Astrophysics Data System (ADS)

    Sohn, D. H.; Shin, Y. H.; Cho, J. H.; Park, J. U.

    2009-04-01

    Under the frame of the Global Earth Observation System of Systems (GEOSS), we are developing a GPS Precipitable Water Vapor (PWV) Information System (IS) of the Decision Making Support System (DMSS) Prototype for Typhoon-Flood Disaster, funded by the Korea Research Council of Fundamental Science and Technology. The system is highly demanded because most, about 90%, of natural disasters happening in Korea have been caused by water, i.e. typhoon, flood, heavy rain and snow, etc. The DMSS prototype, developed mainly by the Korea Information Science and Technology Institute, consists of three sub-systems: observation, prediction, and assessment systems, which are based on the technology of data grid, computation grid, and access grid, respectively. With the augmented reality technology applied, the DMSS web portal that integrates the sub-systems will help the decision makers to access to the DMSS effectively. The GPS PWV IS is being developed as a component of the DMSS prototype for Typhoon-Flood Disaster. PWV estimated from GPS signal delay could be useful to enhance the reliability in numerical weather prediction, nowcasting, climate change monitoring, and so on. As a leading group on GPS Meteorology, the Korea Astronomy and Space Science Institute (KASI) is taking a charge of the GPS PWV IS development. The system will provide the near-real time PWV information based on the nine permanent GPS stations of KASI. Each GPS station of KASI equipped digital weather sensor and provided their own data to the center of KASI in real time. They are expected to be used for operational weather forecasting, researches, instrument validation, etc. Here we introduce the current and future status of our GPS PWV IS, presenting its detailed structures such as Meta Data and Data Base structure, data processing strategy and procedure, flow of information, and application of augmented reality technology.

  4. The time keeping system for GPS block IIR

    NASA Technical Reports Server (NTRS)

    Rawicz, H. C.; Epstein, M. A.; Rajan, J. A.

    1993-01-01

    The precision time keeping system (TKS) in the Global Positioning System (GPS), Block IIR satellites is designed to operate under severe natural and man made environmental conditions. The Block IIR TKS provides precise, autonomous time keeping for periods of up to seven months, without the intervention of the GPS Control Segment. The TKS is implemented using both linear and non-linear controls. The resulting TKS architecture uses a hybrid analog/digital phase locked loop (PLL). The paper provides details of the design and analysis of the TKS. The simulation techniques and the test bed activities used in performing the TKS design trade-offs are described. The effects of non-linear controls are analyzed using a TKS computer simulation of the PLL. The results from a hardware test bed are provided that verify desired TKS operation. The design criteria for the TKS computer simulation and the hardware test bed are indicated. The concepts for verification and testing of the TKS computer simulation and hardware test bed are presented.

  5. Receiver System: Lessons Learned From Solar Two

    SciTech Connect

    LITWIN, ROBERT Z.; PACHECO, JAMES E.

    2002-03-01

    The Boeing Company fabricated the Solar Two receiver as a subcontractor for the Solar Two project. The receiver absorbed sunlight reflected from the heliostat field. A molten-nitrate-salt heat transfer fluid was pumped from a storage tank at grade level, heated from 290 to 565 C by the receiver mounted on top of a tower, then flowed back down into another storage tank. To make electricity, the hot salt was pumped through a steam generator to produce steam that powered a conventional Rankine steam turbine/generator. This evaluation identifies the most significant Solar Two receiver system lessons learned from the Mechanical Design, Instrumentation and Control, Panel Fabrication, Site Construction, Receiver System Operation, and Management from the perspective of the receiver designer/manufacturer. The lessons learned on the receiver system described here consist of two parts: the Problem and one or more identified Solutions. The appendix summarizes an inspection of the advanced receiver panel developed by Boeing that was installed and operated in the Solar Two receiver.

  6. Spaceborne GPS Current Status and Future Visions

    NASA Technical Reports Server (NTRS)

    Bauer, Frank H.; Hartman, Kate; Lightsey, E. Glenn

    1998-01-01

    The Global Positioning System (GPS), developed by the Department of Defense, is quickly revolutionizing the architecture of future spacecraft and spacecraft systems. Significant savings in spacecraft life cycle cost, in power, and in mass can be realized by exploiting Global Positioning System (GPS) technology in spaceborne vehicles. These savings are realized because GPS is a systems sensor-it combines the ability to sense space vehicle trajectory, attitude, time, and relative ranging between vehicles into one package. As a result, a reduced spacecraft sensor complement can be employed on spacecraft and significant reductions in space vehicle operations cost can be realized through enhanced on- board autonomy. This paper provides an overview of the current status of spaceborne GPS, a description of spaceborne GPS receivers available now and in the near future, a description of the 1997-1999 GPS flight experiments and the spaceborne GPS team's vision for the future.

  7. Altimetry Using GPS-Reflection/Occultation Interferometry

    NASA Technical Reports Server (NTRS)

    Cardellach, Estel; DeLaTorre, Manuel; Hajj, George A.; Ao, Chi

    2008-01-01

    A Global Positioning System (GPS)- reflection/occultation interferometry was examined as a means of altimetry of water and ice surfaces in polar regions. In GPS-reflection/occultation interferometry, a GPS receiver aboard a satellite in a low orbit around the Earth is used to determine the temporally varying carrier- phase delay between (1) one component of a signal from a GPS transmitter propagating directly through the atmosphere just as the GPS transmitter falls below the horizon and (2) another component of the same signal, propagating along a slightly different path, reflected at glancing incidence upon the water or ice surface.

  8. 76 FR 67019 - Eighty-Seventh: RTCA Special Committee 159: Global Positioning System (GPS)

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-10-28

    ... Federal Aviation Administration Eighty-Seventh: RTCA Special Committee 159: Global Positioning System (GPS... RTCA Special Committee 159 meeting: Global Positioning System (GPS). SUMMARY: The FAA is issuing this notice to advise the public of a meeting of RTCA Special Committee 159: Global Positioning System...

  9. 77 FR 12106 - 88th Meeting: RTCA Special Committee 159, Global Positioning System (GPS)

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-02-28

    ... Federal Aviation Administration 88th Meeting: RTCA Special Committee 159, Global Positioning System (GPS... RTCA Special Committee 159, Global Positioning System (GPS). SUMMARY: The FAA is issuing this notice to advise the public of the 88th meeting of RTCA Special Committee 159, Global Positioning System...

  10. 78 FR 68861 - Certain Navigation Products, Including GPS Devices, Navigation and Display Systems, Radar Systems...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-11-15

    ..., Navigational Aids, Mapping Systems and Related Software; Institution of Investigation Pursuant to 19 U.S.C... and display systems, radar systems, navigational aids, mapping systems and related software by reason... products, including GPS devices, navigation and display systems, radar systems, navigational aids,...

  11. Georeferencing airborne images from a multiple digital camera system by GPS/INS

    NASA Astrophysics Data System (ADS)

    Mostafa, Mohamed Mohamed Rashad

    2000-10-01

    In this thesis, the development and testing of an airborne fully digital multi-sensor system for kinematic mapping is presented. The system acquires two streams of data, namely navigation data and imaging data. The navigation data are obtained by integrating an accurate strapdown Inertial Navigation System with two GPS receivers. The imaging data are acquired by two digital cameras, configured in such a way so as to reduce their geometric limitations. The two digital cameras capture strips of overlapping nadir and oblique images. The INS/GPS-derived trajectory contains the full translational and rotational motion of the carrier aircraft. Thus, image exterior orientation information is extracted from the trajectory, during postprocessing. This approach eliminates the need for ground control when computing 3D positions of objects that appear in the field of view of the system imaging component. Test flights were conducted over the campus of The University of Calgary. Two approaches for calibrating the system are presented, namely pre-mission calibration and in-flight calibration. Testing the system in flight showed that best ground point positioning accuracy at 1:12000 average image scale is 0.2 m (RMS) in easting and northing and 0.3 m (RMS) in height. Preliminary results indicate that major applications of such a system in the future are in the field of digital mapping, at scales of 1:10000 and smaller, and the generation of digital elevation models for engineering applications.

  12. Space Shuttle Global Positioning System (GPS) testing at NASA Johnson Space Center

    NASA Technical Reports Server (NTRS)

    Pawlowski, J. F.; Quinn, M.

    1982-01-01

    The present investigation is concerned with the significance of the use of the Global Positioning System (GPS) for the Space Shuttle. On the basis of a study regarding the use of the GPS on the Space Shuttle, it was decided that such a system would greatly benefit Space Shuttle navigation. Studies with GPS user equipment were, therefore, conducted to obtain data and information which would provide a base for the formulation and the further refinement of NASA requirements with respect to the type of set the Shuttle would need. Attention is given to orbit determination, satellite numbers, background information concerning the GPS, the currently available GPS sets, the conducted studies, Shuttle sonic boom recording sites, tests performed with the aid of the Kuiper airborne observatory, and questions regarding the test applicability to Shuttle GPS.

  13. Spaceborne GPS: Current Status and Future Visions

    NASA Technical Reports Server (NTRS)

    Bauer, Frank H.; Hartman, Kate; Lightsey, E. Glenn

    1998-01-01

    The Global Positioning System (GPS), developed by the Department of Defense is quickly revolutionizing the architecture of future spacecraft and spacecraft systems. Significant savings in spacecraft life cycle cost, in power, and in mass can be realized by exploiting GPS technology in spaceborne vehicles. These savings are realized because GPS is a systems sensor--it combines the ability to sense space vehicle trajectory, attitude, time, and relative ranging between vehicles into one package. As a result, a reduced spacecraft sensor complement can be employed and significant reductions in space vehicle operations cost can be realized through enhanced on-board autonomy. This paper provides an overview of the current status of spaceborne GPS, a description of spaceborne GPS receivers available now and in the near future, a description of the 1997-2000 GPS flight experiments, and the spaceborne GPS team's vision for the future.

  14. Solar central receiver systems comparative economics

    NASA Astrophysics Data System (ADS)

    Eicker, P. J.

    1980-04-01

    Several major conceptual design studies of solar central receiver systems and components were completed in the last year. The results of these studies were used to compare the projected cost of electric power generation using central receiver systems with that of more conventional power generation. The cost estimate for a molten salt central receiver system is given. Levelized busbar energy cost is shown as a function of annual capacity factor indicating the fraction of the cost due to each of the subsystems. The estimated levelized busbar energy cost for a central receiver (70 to 90 mills per kilowatt hour) is compared with the levelized busbar energy cost for a new coal fired Rankine cycle plant. Sensitivities to the initial cost of coal and the delta fuel escalation are shown.

  15. Solar central receiver systems comparative economics

    SciTech Connect

    Eicker, P J

    1980-04-01

    Several major conceptual design studies of solar central receiver systems and components have been completed in the last year. The results of these studies are used to compare the projected cost of electric power generation using central receiver systems with that of more conventional power generation. The cost estimate for a molten salt central receiver system is given. Levelized busbar energy cost is shown as a function of annual capacity factor indicating the fraction of the cost due to each of the subsystems. The estimated levelized busbar energy cost for a central receiver (70 to 90 mills per kilowatt hour) is compared with the levelized busbar energy cost for a new coal fired Rankine cycle plant. Sensitivities to the initial cost of coal and the delta fuel escalation are shown. (WHK)

  16. On Fast Post-Processing of Global Positioning System Simulator Truth Data and Receiver Measurements and Solutions Data

    NASA Technical Reports Server (NTRS)

    Kizhner, Semion; Day, John H. (Technical Monitor)

    2000-01-01

    Post-processing of data, related to a GPS receiver test in a GPS simulator and test facility, is an important step towards qualifying a receiver for space flight. Although the GPS simulator provides all the parameters needed to analyze a simulation, as well as excellent analysis tools on the simulator workstation, post-processing is not a GPS simulator or receiver function alone, and it must be planned as a separate pre-flight test program requirement. A GPS simulator is a critical resource, and it is desirable to move off the pertinent test data from the simulator as soon as a test is completed. The receiver and simulator databases are used to extract the test data files for postprocessing. These files are then usually moved from the simulator and receiver systems to a personal computer (PC) platform, where post-processing is done typically using PC-based commercial software languages and tools. Because of commercial software systems generality their functions are notoriously slow and more than often are the bottleneck even for short duration simulator-based tests. There is a need to do post-processing faster and within an hour after test completion, including all required operations on the simulator and receiver to prepare and move off the post-processing files. This is especially significant in order to use the previous test feedback for the next simulation setup or to run near back-to-back simulation scenarios. Solving the post-processing timing problem is critical for a pre-flight test program success. Towards this goal an approach was developed that allows to speed-up post-processing by an order of a magnitude. It is based on improving the post-processing bottleneck function algorithm using a priory information that is specific to a GPS simulation application and using only the necessary volume of truth data. The presented postprocessing scheme was used in support of a few successful space flight missions carrying GPS receivers.

  17. 77 FR 13350 - Certain Automotive GPS Navigation Systems, Components Thereof, and Products Containing Same...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-03-06

    ... complaint filed by Beacon Navigation GmbH of Zug, Switzerland (``Beacon''). 76 FR 72443 (Nov. 23, 2011). The... COMMISSION Certain Automotive GPS Navigation Systems, Components Thereof, and Products Containing Same... importation of certain automotive GPS navigation systems, components thereof, and products containing the...

  18. A Low Cost GPS System for Real-Time Tracking of Sounding Rockets

    NASA Technical Reports Server (NTRS)

    Markgraf, M.; Montenbruck, O.; Hassenpflug, F.; Turner, P.; Bull, B.; Bauer, Frank (Technical Monitor)

    2001-01-01

    In an effort to minimize the need for costly, complex, tracking radars, the German Space Operations Center has set up a research project for GPS based tracking of sounding rockets. As part of this project, a GPS receiver based on commercial technology for terrestrial applications has been modified to allow its use under the highly dynamical conditions of a sounding rocket flight. In addition, new antenna concepts are studied as an alternative to proven but costly wrap-around antennas.

  19. A Tightly-Coupled GPS/INS/UWB Cooperative Positioning Sensors System Supported by V2I Communication.

    PubMed

    Wang, Jian; Gao, Yang; Li, Zengke; Meng, Xiaolin; Hancock, Craig M

    2016-01-01

    This paper investigates a tightly-coupled Global Position System (GPS)/Ultra-Wideband (UWB)/Inertial Navigation System (INS) cooperative positioning scheme using a Robust Kalman Filter (RKF) supported by V2I communication. The scheme proposes a method that uses range measurements of UWB units transmitted among the terminals as augmentation inputs of the observations. The UWB range inputs are used to reform the GPS observation equations that consist of pseudo-range and Doppler measurements and the updated observation equation is processed in a tightly-coupled GPS/UWB/INS integrated positioning equation using an adaptive Robust Kalman Filter. The result of the trial conducted on the roof of the Nottingham Geospatial Institute (NGI) at the University of Nottingham shows that the integrated solution provides better accuracy and improves the availability of the system in GPS denied environments. RKF can eliminate the effects of gross errors. Additionally, the internal and external reliabilities of the system are enhanced when the UWB observables received from the moving terminals are involved in the positioning algorithm. PMID:27355947

  20. A Tightly-Coupled GPS/INS/UWB Cooperative Positioning Sensors System Supported by V2I Communication

    PubMed Central

    Wang, Jian; Gao, Yang; Li, Zengke; Meng, Xiaolin; Hancock, Craig M.

    2016-01-01

    This paper investigates a tightly-coupled Global Position System (GPS)/Ultra-Wideband (UWB)/Inertial Navigation System (INS) cooperative positioning scheme using a Robust Kalman Filter (RKF) supported by V2I communication. The scheme proposes a method that uses range measurements of UWB units transmitted among the terminals as augmentation inputs of the observations. The UWB range inputs are used to reform the GPS observation equations that consist of pseudo-range and Doppler measurements and the updated observation equation is processed in a tightly-coupled GPS/UWB/INS integrated positioning equation using an adaptive Robust Kalman Filter. The result of the trial conducted on the roof of the Nottingham Geospatial Institute (NGI) at the University of Nottingham shows that the integrated solution provides better accuracy and improves the availability of the system in GPS denied environments. RKF can eliminate the effects of gross errors. Additionally, the internal and external reliabilities of the system are enhanced when the UWB observables received from the moving terminals are involved in the positioning algorithm. PMID:27355947

  1. Development of a Fully Automated, GPS Based Monitoring System for Disaster Prevention and Emergency Preparedness: PPMS+RT

    PubMed Central

    Bond, Jason; Kim, Don; Chrzanowski, Adam; Szostak-Chrzanowski, Anna

    2007-01-01

    The increasing number of structural collapses, slope failures and other natural disasters has lead to a demand for new sensors, sensor integration techniques and data processing strategies for deformation monitoring systems. In order to meet extraordinary accuracy requirements for displacement detection in recent deformation monitoring projects, research has been devoted to integrating Global Positioning System (GPS) as a monitoring sensor. Although GPS has been used for monitoring purposes worldwide, certain environments pose challenges where conventional processing techniques cannot provide the required accuracy with sufficient update frequency. Described is the development of a fully automated, continuous, real-time monitoring system that employs GPS sensors and pseudolite technology to meet these requirements in such environments. Ethernet and/or serial port communication techniques are used to transfer data between GPS receivers at target points and a central processing computer. The data can be processed locally or remotely based upon client needs. A test was conducted that illustrated a 10 mm displacement was remotely detected at a target point using the designed system. This information could then be used to signal an alarm if conditions are deemed to be unsafe.

  2. Autonomous reconfigurable GPS/INS navigation and pointing system for rendezvous and docking

    NASA Technical Reports Server (NTRS)

    Upadhyay, Triveni N.; Cotterill, Stephen; Deaton, A. Wayne

    1991-01-01

    This paper describes the results of an integrated navigation and pointing system software development effort sponsored by the NASA MSFC through a SBIR Phase 2 Program. The integrated Global Positioning System (GPS)/Inertial Navigation System (INS) implements an autonomous navigation filter that is reconfigurable in real-time to accommodate mission contingencies. An onboard expert system monitors the spacecraft status and reconfigures the navigation filter accordingly, to optimize the system performance. The navigation filter is a multi-mode Kalman filter to estimate the spacecraft position, velocity, and attitude. Three different GPS-based attitude determination techniques, namely, velocity vector matching, attitude vector matching, and interferometric processing, are implemented to encompass different mission contingencies. The integrated GPS/INS navigation filter will use any of these techniques depending on the mission phase and the state of the sensors. The first technique, velocity vector matching, uses the GPS velocity measurement to estimate the INS velocity errors and exploits the correlation between INS velocity and attitude errors to estimate the attitude. The second technique, attitude vector matching, uses INS gyro measurements and GPS carrier phase (integrated Doppler) measurements during a spacecraft rotation maneuver to determine the attitude. Both of these techniques require only one GPS antenna onboard to determine the spacecraft attitude. The third technique, interferometric processing, requires use of multiple GPS antennae. In order to determine 3-axis body attitude, three GPS antennae (2 no-coplanor baselines) are required.

  3. Performance analysis of a GPS Interferometric attitude determination system for a gravity gradient stabilized spacecraft. M.S. Thesis

    NASA Technical Reports Server (NTRS)

    Stoll, John C.

    1995-01-01

    The performance of an unaided attitude determination system based on GPS interferometry is examined using linear covariance analysis. The modelled system includes four GPS antennae onboard a gravity gradient stabilized spacecraft, specifically the Air Force's RADCAL satellite. The principal error sources are identified and modelled. The optimal system's sensitivities to these error sources are examined through an error budget and by varying system parameters. The effects of two satellite selection algorithms, Geometric and Attitude Dilution of Precision (GDOP and ADOP, respectively) are examined. The attitude performance of two optimal-suboptimal filters is also presented. Based on this analysis, the limiting factors in attitude accuracy are the knowledge of the relative antenna locations, the electrical path lengths from the antennae to the receiver, and the multipath environment. The performance of the system is found to be fairly insensitive to torque errors, orbital inclination, and the two satellite geometry figures-of-merit tested.

  4. Definition study of land/sea civil user navigational location monitoring systems for NAVSTAR GPS: User requirements and systems concepts

    NASA Technical Reports Server (NTRS)

    Devito, D. M.

    1981-01-01

    A low-cost GPS civil-user mobile terminal whose purchase cost is substantially an order of magnitude less than estimates for the military counterpart is considered with focus on ground station requirements for position monitoring of civil users requiring this capability and the civil user navigation and location-monitoring requirements. Existing survey literature was examined to ascertain the potential users of a low-cost NAVSTAR receiver and to estimate their number, function, and accuracy requirements. System concepts are defined for low cost user equipments for in-situ navigation and the retransmission of low data rate positioning data via a geostationary satellite to a central computing facility.

  5. Simulation and analysis of differential GPS

    NASA Astrophysics Data System (ADS)

    Denaro, R. P.

    NASA is conducting a research program to evaluate differential Global Positioning System (GPS) concepts for civil helicopter navigation. It is pointed out that the civil helicopter community will probably be an early user of GPS because of the unique mission operations in areas where precise navigation aids are not available. However, many of these applications involve accuracy requirements which cannot be satisfied by conventional GPS. Such applications include remote area search and rescue, offshore oil platform approach, remote area precision landing, and other precise navigation operations. Differential GPS provides a promising approach for meeting very demanding accuracy requirements. The considered procedure eliminates some of the common bias errors experienced by conventional GPS. This is done by making use of a second GPS receiver. A simulation process is developed as a tool for analyzing various scenarios of GPS-referenced civil aircraft navigation.

  6. Simulation and analysis of differential GPS

    NASA Technical Reports Server (NTRS)

    Denaro, R. P.

    1984-01-01

    NASA is conducting a research program to evaluate differential Global Positioning System (GPS) concepts for civil helicopter navigation. It is pointed out that the civil helicopter community will probably be an early user of GPS because of the unique mission operations in areas where precise navigation aids are not available. However, many of these applications involve accuracy requirements which cannot be satisfied by conventional GPS. Such applications include remote area search and rescue, offshore oil platform approach, remote area precision landing, and other precise navigation operations. Differential GPS provides a promising approach for meeting very demanding accuracy requirements. The considered procedure eliminates some of the common bias errors experienced by conventional GPS. This is done by making use of a second GPS receiver. A simulation process is developed as a tool for analyzing various scenarios of GPS-referenced civil aircraft navigation.

  7. Accuracy analysis on C/A code and P(Y) code pseudo-range of GPS dual frequency receiver and application in point positioning

    NASA Astrophysics Data System (ADS)

    Peng, Xiuying; Fan, Shijie; Guo, Jiming

    2008-10-01

    When the Anti-Spoofing (A-S) is active, the civilian users have some difficulties in using the P(Y) code for precise navigation and positioning. Z-tracking technique is one of the effective methods to acquire the P(Y) code. In this paper, the accuracy of pseudoranges from C/A code and P(Y) code for dual frequency GPS receiver is discussed. The principle of measuring the encrypted P(Y) code is described firstly, then a large data set from IGS tracking stations is utilized for analysis and verification with the help of a precise point positioning software developed by authors. Especially, P(Y) code pseudoranges of civilian GPS receivers allow eliminating/reducing the effect of ionospheric delay and improve the precision of positioning. The point positioning experiments for this are made in the end.

  8. Emergency Locating Transmitter and Receiver System

    NASA Technical Reports Server (NTRS)

    Wren, Paul E. (Inventor)

    1988-01-01

    A receiver and transmitter are provided for a distress incident locating telecommunications system. The receiver is a superheterodyne AM receiver which applies the received distress transmissions to a normally unlocked phaselock loop which locks onto the unmodulated carrier signal portion of the distress transmission. The duration of the phaselock loop being locked, and unlocked immediately after being locked, are measured and compared to predetermined values to find a match. Each of the predetermined values corresponds to an item of information, and if a match is found, the receiver indicates it. The receiver is also capable of extracting audio information present in the distress transmission. The transmitter generates three signals which can be applied to a transmitting antenna. These signals are a radio frequency carrier signal, and a carrier signal modulated by a distress waveform or by an audio signal. The signal which is ultimately applied to the transmitting antenna will have four parameters where each set of parameters corresponds to a different item of information. The parameters are which one or more of the three signals will be applied to the antenna, the sequence of application of the signals to the antenna, the duration of each of the signals, and the frequency of the audio signal.

  9. A worldwide unification of GPS (Global Positioning System) antenna coordinates for high accuracy time transfer.

    NASA Astrophysics Data System (ADS)

    Lewandowski, W.

    In the present state of the art of atomic clocks it is desirable that comparisons of these clocks, located in the time metrology laboratories spread around the world, be at the level of a few nanoseconds of accuracy. At present the sole operational way to provide such performance is through the system of GPS satellites. As GPS is a one-way system this implies that special attention must be given to geometrical errors. In order to achieve nanosecond accuracy, the error due to the ground-antenna coordinates should not exceed 1 ns in the global budget of errors of GPS time transfer. To attain this goal the ground-antenna coordinates must be accurately determined in a common worldwide homogeneous geodetic reference frame with uncertainties of order 30 cm. This paper considers the choice of a global reference frame for accurate GPS time transfer and then reports on a worldwide homogenization of GPS antenna coordinates in the principal timing centres.

  10. Modular Software for Spacecraft Navigation Using the Global Positioning System (GPS)

    NASA Technical Reports Server (NTRS)

    Truong, S. H.; Hartman, K. R.; Weidow, D. A.; Berry, D. L.; Oza, D. H.; Long, A. C.; Joyce, E.; Steger, W. L.

    1996-01-01

    The Goddard Space Flight Center Flight Dynamics and Mission Operations Divisions have jointly investigated the feasibility of engineering modular Global Positioning SYSTEM (GPS) navigation software to support both real time flight and ground postprocessing configurations. The goals of this effort are to define standard GPS data interfaces and to engineer standard, reusable navigation software components that can be used to build a broad range of GPS navigation support applications. The paper discusses the GPS modular software (GMOD) system and operations concepts, major requirements, candidate software architecture, feasibility assessment and recommended software interface standards. In additon, ongoing efforts to broaden the scope of the initial study and to develop modular software to support autonomous navigation using GPS are addressed,

  11. Geomagnetic storms, super-storms, and their impacts on GPS-based navigation systems

    NASA Astrophysics Data System (ADS)

    Astafyeva, E.; Yasyukevich, Yu.; Maksikov, A.; Zhivetiev, I.

    2014-07-01

    Using data of GPS receivers located worldwide, we analyze the quality of GPS performance during four geomagnetic storms of different intensity: two super-storms and two intense storms. We show that during super-storms the density of GPS Losses-of-Lock (LoL) increases up to 0.25% at L1 frequency and up to 3% at L2 frequency, and up to 0.15% (at L1) and 1% (at L2) during less intense storms. Also, depending on the intensity of the storm time ionospheric disturbances, the total number of total electron content (TEC) slips can exceed from 4 to 40 times the quiet time level. Both GPS LoL and TEC slips occur during abrupt changes of SYM-H index of geomagnetic activity, i.e., during the main phase of geomagnetic storms and during development of ionospheric storms. The main contribution in the total number of GPS LoL was found to be done by GPS sites located at low and high latitudes, whereas the area of numerous TEC slips seemed to mostly correspond to the boundary of the auroral oval, i.e., region with intensive ionospheric irregularities. Our global maps of TEC slips show where the regions with intense irregularities of electron density occur during geomagnetic storms and will let us in future predict appearance of GPS errors for geomagnetically disturbed conditions.

  12. Using different pseudorange measurements to evaluate the performance of GPS-based navigation systems during Geomagnetic storms

    NASA Astrophysics Data System (ADS)

    Adewale, Adekola; Oyeyemi, Elijah

    2016-07-01

    The space and ground-based Global Positioning System (GPS) are vulnerable to a variety of space weather effects, particularly effects due to geomagnetic storms, and as such, signals from the systems suffer degradation during propagation through the ionosphere. A comparison of GPS positioning 3-D vertical (MRSE) and horizontal (DRMS) root mean square positioning errors obtained from different pseudorange measurements at low and high latitude stations has been done. GPS observation data were processed and analyzed from 6th-12th November, 2004, using different pseudorange measurements i.e., L1 C/A, L1 P, L2 P codes and ionosphere-free combination ((C/A on L1 and P on L2) and (P on L1 and P on L2)). Our results show that geomagnetic storms have impact on navigation at low and high latitude stations. This work also shows that GPS receivers can record significant positioning error during magnetically quiet days and with ionosphere-free pseudorange measurement.

  13. Wireless GPS system for module-level fiber quality mapping: System improvement and field testing

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A wireless GPS system for module-level fiber quality mapping has been developed at Texas A&M University. In its complete form, it includes subsystems for harvesters, boll buggies, and module builders. The system was field tested on a producer’s farm near Plains, Texas, in 2006. The field test identi...

  14. Wireless GPS system for module fiber quality mapping: System improvement and field testing

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A wireless GPS system for module-level fiber quality mapping has been developed at Texas A&M University. In its complete form, it includes subsystems for harvesters, boll buggies, and module builders. The system was field tested on a producer's farm near Plains, Texas, in 2006. The field test identi...

  15. Integrated GPS/INS navigation system design for autonomous spacecraft rendezvous

    NASA Astrophysics Data System (ADS)

    Gaylor, David Edward

    2003-10-01

    The goal of the NASA Space Launch Initiative (SLI) program is to advance the technologies for the next generation reusable launch vehicle (RLV). The SLI program has identified automated rendezvous and docking as an area requiring further research and development. Currently, the Space Shuttle uses a partially manual system for rendezvous, but a fully automated system could be safer and more reliable. Previous studies have shown that it is feasible to use the Global Positioning System (GPS) for spacecraft navigation during rendezvous with the International Space Station (ISS). However, these studies have not accounted for the effects of GPS signal blockage and multipath in the vicinity of the ISS, which make a GPS-only navigation system less accurate and reliable. One possible solution is to combine GPS with an inertial navigation system (INS). The integration of GPS and INS can be achieved using a Kalman filter. GPS/INS systems have been used in aircraft for many years and have also been used in launch vehicles. However, the performance of GPS/INS systems in orbit and during spacecraft rendezvous has not been characterized. The primary objective of this research is to evaluate the ability of an integrated GPS/INS to provide accurate navigation solutions during a rendezvous scenario where the effects of ISS signal blockage, multipath and delta-v maneuvers degrade GPS-only navigation. In order to accomplish this, GPS-only and GPS/INS Kalman filters have been developed for both absolute and relative navigation, as well as a new statistical multipath model for spacecraft operating near the ISS. Several factors that affect relative navigation performance were studied, including: filter tuning, GPS constellation geometry, rendezvous approach direction, and inertial sensor performance. The results showed that each of these factors has a large impact on relative navigation performance. Finally, it has been demonstrated that a GPS/INS system based on medium accuracy aircraft

  16. How useful is satellite positioning system (GPS) to track gait parameters? A review

    PubMed Central

    Terrier, Philippe; Schutz, Yves

    2005-01-01

    Over the last century, numerous techniques have been developed to analyze the movement of humans while walking and running. The combined use of kinematics and kinetics methods, mainly based on high speed video analysis and forceplate, have permitted a comprehensive description of locomotion process in terms of energetics and biomechanics. While the different phases of a single gait cycle are well understood, there is an increasing interest to know how the neuro-motor system controls gait form stride to stride. Indeed, it was observed that neurodegenerative diseases and aging could impact gait stability and gait parameters steadiness. From both clinical and fundamental research perspectives, there is therefore a need to develop techniques to accurately track gait parameters stride-by-stride over a long period with minimal constraints to patients. In this context, high accuracy satellite positioning can provide an alternative tool to monitor outdoor walking. Indeed, the high-end GPS receivers provide centimeter accuracy positioning with 5–20 Hz sampling rate: this allows the stride-by-stride assessment of a number of basic gait parameters – such as walking speed, step length and step frequency – that can be tracked over several thousand consecutive strides in free-living conditions. Furthermore, long-range correlations and fractal-like pattern was observed in those time series. As compared to other classical methods, GPS seems a promising technology in the field of gait variability analysis. However, relative high complexity and expensiveness – combined with a usability which requires further improvement – remain obstacles to the full development of the GPS technology in human applications. PMID:16138922

  17. Combining low-cost GPS receivers with upGPR to derive continuously liquid water content, snow height and snow water equivalent in Alpine snow covers

    NASA Astrophysics Data System (ADS)

    Koch, Franziska; Schmid, Lino; Prasch, Monika; Heilig, Achim; Eisen, Olaf; Schweizer, Jürg; Mauser, Wolfram

    2015-04-01

    The temporal evolution of Alpine snowpacks is important for assessing water supply, hydropower generation, flood predictions and avalanche forecasts. Especially in high mountain regions with an extremely varying topography, it is until now often difficult to derive continuous and non-destructive information on snow parameters. Since autumn 2012, we are running a new low-cost GPS (Global Positioning System) snow measurement experiment at the high alpine study site Weissfluhjoch (2450 m a.s.l.) in Switzerland. The globally and freely broadcasted GPS L1-band (1.57542 GHz) was continuously recorded with GPS antennas, which are installed at the ground surface underneath the snowpack. GPS raw data, containing carrier-to-noise power density ratio (C/N0) as well as elevation and azimuth angle information for each time step of 1 s, was stored and analyzed for all 32 GPS satellites. Since the dielectric permittivity of an overlying wet snowpack influences microwave radiation, the bulk volumetric liquid water content as well as daily melt-freeze cycles can be derived non-destructively from GPS signal strength losses and external snow height information. This liquid water content information is qualitatively in good accordance with meteorological and snow-hydrological data and quantitatively highly agrees with continuous data derived from an upward-looking ground-penetrating radar (upGPR) working in a similar frequency range. As a promising novelty, we combined the GPS signal strength data with upGPR travel-time information of active impulse radar rays to the snow surface and back from underneath the snow cover. This combination allows determining liquid water content, snow height and snow water equivalent from beneath the snow cover without using any other external information. The snow parameters derived by combining upGPR and GPS data are in good agreement with conventional sensors as e.g. laser distance gauges or snow pillows. As the GPS sensors are cheap, they can easily

  18. a New Survey on Self-Tuning Integrated Low-Cost Gps/ins Vehicle Navigation System in Harsh Environment

    NASA Astrophysics Data System (ADS)

    Navidi, N.; Landry, R., Jr.

    2015-08-01

    Nowadays, Global Positioning System (GPS) receivers are aided by some complementary radio navigation systems and Inertial Navigation Systems (INS) to obtain more accuracy and robustness in land vehicular navigation. Extended Kalman Filter (EKF) is an acceptable conventional method to estimate the position, the velocity, and the attitude of the navigation system when INS measurements are fused with GPS data. However, the usage of the low-cost Inertial Measurement Units (IMUs) based on the Micro-Electro-Mechanical Systems (MEMS), for the land navigation systems, reduces the precision and stability of the navigation system due to their inherent errors. The main goal of this paper is to provide a new model for fusing low-cost IMU and GPS measurements. The proposed model is based on EKF aided by Fuzzy Inference Systems (FIS) as a promising method to solve the mentioned problems. This model considers the parameters of the measurement noise to adjust the measurement and noise process covariance. The simulation results show the efficiency of the proposed method to reduce the navigation system errors compared with EKF.

  19. Compensating For GPS Ephemeris Error

    NASA Technical Reports Server (NTRS)

    Wu, Jiun-Tsong

    1992-01-01

    Method of computing position of user station receiving signals from Global Positioning System (GPS) of navigational satellites compensates for most of GPS ephemeris error. Present method enables user station to reduce error in its computed position substantially. User station must have access to two or more reference stations at precisely known positions several hundred kilometers apart and must be in neighborhood of reference stations. Based on fact that when GPS data used to compute baseline between reference station and user station, vector error in computed baseline is proportional ephemeris error and length of baseline.

  20. Monitoring mobility in older adults using global positioning system (GPS) watches and accelerometers: a feasibility study.

    PubMed

    Webber, Sandra C; Porter, Michelle M

    2009-10-01

    This exploratory study examined the feasibility of using Garmin global positioning system (GPS) watches and ActiGraph accelerometers to monitor walking and other aspects of community mobility in older adults. After accuracy at slow walking speeds was initially determined, 20 older adults (74.4 +/- 4.2 yr) wore the devices for 1 day. Steps, distances, and speeds (on foot and in vehicle) were determined. GPS data acquisition varied from 43 min to over 12 hr, with 55% of participants having more than 8 hr between initial and final data-collection points. When GPS data were acquired without interruptions, detailed mobility information was obtained regarding the timing, distances covered, and speeds reached during trips away from home. Although GPS and accelerometry technology offer promise for monitoring community mobility patterns, new GPS solutions are required that allow for data collection over an extended period of time between indoor and outdoor environments. PMID:19940324

  1. Recovery of a geocentric reference frame using the present-day GPS system

    NASA Technical Reports Server (NTRS)

    Malla, Rajendra P.; Wu, Sien-Chong

    1990-01-01

    A geocentric reference frame adopts the center of mass of the earth as the origin of the coordinate axes. The center of mass of the earth is the natural and unambiguous origin of a geocentric satellite dynamical system. But in practice a kinematically obtained terrestrial reference frame may assume an origin other than the geocenter. The establishment of a geocentric reference frame, to which all relevant observations and results can be referred and in which geodynamic theories or models for the dynamic behavior of earth can be formulated, requires the ability to accurately recover a given coordinate frame origin offset from the geocenter. GPS measurements, because of their abundance and broad distribution, provide a powerful tool to obtain this origin offset in a short period of time. Two effective strategies have been devised. Data from the First Central And South America (Casa Uno) geodynamics experiment has been studied, in order to demonstrate the ability of recovering the geocenter location with present day GPS satellites and receivers.

  2. Tracking the movement of Hawaiian volcanoes; Global Positioning System (GPS) measurement

    USGS Publications Warehouse

    Dvorak, J.J.

    1992-01-01

    At some well-studied volcanoes, surface movements of at least several centimeters take place out to distances of about 10 km from the summit of the volcano. Widespread deformation of this type is relatively easy to monitor, because the necessary survey stations can be placed at favorable sites some distance from the summit of the volcano. Examples of deformation of this type include Kilauea and Mauna Loa in Hawaii, Krafla in Iceland, Long Valley in California, Camp Flegrei in Italy, and Sakurajima in Japan. In contrast, surface movement at some other volcanoes, usually volcanoes with steep slopes, is restricted to places within about 1 km of their summits. Examples of this class of volcanoes include Mount St. Helens in Washington, Etna in Italy, and Tangkuban Parahu in Indonesia. Local movement on remote, rugged volcanoes of this type is difficult to observe using conventional methods of measuring ground movement, which generally require a clear line-of-sight between points of interest. However, a revolutionary new technique, called the Global Positional System (GPS), provides a very efficient, alternative method of making such measurements. GPS, which uses satellites and ground-based receivers to accurately record slight crustal movements, is rapidly becoming the method of choice to measure deformation at volcanoes. 

  3. GPS/INS Sensor Fusion Using GPS Wind up Model

    NASA Technical Reports Server (NTRS)

    Williamson, Walton R. (Inventor)

    2013-01-01

    A method of stabilizing an inertial navigation system (INS), includes the steps of: receiving data from an inertial navigation system; and receiving a finite number of carrier phase observables using at least one GPS receiver from a plurality of GPS satellites; calculating a phase wind up correction; correcting at least one of the finite number of carrier phase observables using the phase wind up correction; and calculating a corrected IMU attitude or velocity or position using the corrected at least one of the finite number of carrier phase observables; and performing a step selected from the steps consisting of recording, reporting, or providing the corrected IMU attitude or velocity or position to another process that uses the corrected IMU attitude or velocity or position. A GPS stabilized inertial navigation system apparatus is also described.

  4. A design proposal of a certain missile tactical command system based on Beidou satellite communication and GPS positioning techniques

    NASA Astrophysics Data System (ADS)

    Ma, Jian; Hao, Yongsheng; Miao, Jian; Zhang, Jianmao

    2007-11-01

    This paper introduced a design proposal of tactical command system that applied to a kind of anti-tank missile carriers. The tactical command system was made up of embedded computer system based on PC104 bus, Linux operating system, digital military map, Beidou satellite communication equipments and GPS positioning equipments. The geographic coordinates was measured by the GPS receiver, the positioning data, commands and information were transmitted real-time between tactical command systems, tactical command systems and command center, by the Beidou satellite communication systems. The Beidou satellite communication equipments and GPS positioning equipments were integrated to an independent module, exchanging data with embedded computer through RS232 serial ports and USB ports. The decision support system software based on information fusion, calculates positioning data, geography information and battle field information synthetically, shows the position of allies and the position of enemy on the military map, and assesses the various threats of different enemy objects, educes a situation assessment and threat assessment.

  5. Automatic monitoring system for high-steep slope in open-pit mine based on GPS and data analysis

    NASA Astrophysics Data System (ADS)

    Zhou, Chunmei; Li, Xianfu; Qin, Sunwei; Qiu, Dandan; Wu, Yanlin; Xiao, Yun; Zhou, Jian

    2008-12-01

    Recently, GPS has been more and more applicative in open pit mine slope safety monitoring. Daye Iron Mine open pit high-steep slope automatic monitoring system mainly consists of three modules, namely, GPS data processing module, monitoring and warning module, emergency plans module. According to the rock mass structural feature and the side slope stability evaluation, it is arranged altogether to seven GPS distortion monitoring points on the sharp of Fault F9 at Daye iron Mine, adopted the combination of monofrequent static GPS receiver and data-transmission radio to carry on the observation, the data processing mainly uses three transect interpolation method to solve the questions of discontinuity and Effectiveness in the data succession. According to the displacement monitoring data from 1990 to 1996 of Daye Iron Mine East Open Pit Shizi mountain Landslide A2, researching the displacement criterion, rate criterion, acceleration criterion, creep curve tangent angle criterion etc of landslide failure, the result shows that the landslide A2 is the lapse type crag nature landslide whose movement in three phases, namely creep stage, accelerated phase, destruction stage. It is different of the failure criterion in different stages and different position that is at the rear, central, front margin of the landslide. It has important guiding significance to put forward the comprehensive failure criterion of seven new-settled monitoring points combining the slope deformation destruction and macroscopic evidence.

  6. Autonomous reconfigurable GPS/INS navigation and pointing system for rendezvous and docking

    NASA Technical Reports Server (NTRS)

    Upadhyay, T. N.; Cotterill, S.; Deaton, A. W.

    1992-01-01

    This paper describes the development of an autonomous integrated spacecraft navigation system which provides multiple modes of navigation, including relative and absolute navigation. The system provides attitude information from GPS or INS, or by tightly integrating the two systems. Interferometric GPS techniques are used when multiple antennas and integrated Doppler measurements are available. An important aspect of this research is the autonomously reconfigurable Kalman filter, controlled by an embedded knowledge base, designed to respond to component degradation and changes in mission goals.

  7. Instructional Geocaching: An Analysis of GPS Receivers as Tools for Technology Integration into a Middle School Classroom

    ERIC Educational Resources Information Center

    Mayben, Robert Edwin

    2010-01-01

    The purpose of this study was to investigate how the instructional use of GPS through instructional geocaching activities engages students and promotes achievement in a middle school social studies classroom. The impact of instructional geocaching on addressing the needs of students with various learning styles was also examined. In addition, the…

  8. The utilization of Malaysian Active GPS System data for geodynamic applications: a case study in East and West Malaysia

    NASA Astrophysics Data System (ADS)

    Abu Bakar, Rabieahtul; Azahari Razak, Khamarrul

    2010-05-01

    Geodynamic studies of Malaysia have been ventured upon in the South-East Asia region since the first GeodySEA project in 1996. Both East and West Malaysia lies on the Eurasian Plate, and assumed to have no linear distortion between any two joined points relative to one another. However, Malaysia lies at the southern tip of the plate encroached by two frequently ruptured boundaries, the Indian-Australian plate and the Philippines plate, and it is also within the buffer of the Ring of fire. Hence, this paper is essential to determine the relative movement of Malaysia, and with the possibilities to identify the presences of slip-fault formation which might be of threat to the stable platform that we have taken for granted. Availability of uninterrupted GPS observations over the Malaysian Active GPS System known as MASS stations situated across the country established by the Department of Survey and Mapping (DSMM) evidently help provides the data for this study. There are currently eighteen MASS stations mounted with Trimble 4000 dual frequency antenna and data recorded at fine second interval made accessible in hourly files. Satellite data collected continuously over a long period of time are processed by Bernese GPS processing software. Fifteen International GNSS Service (IGS) stations were selected within similar period of observations were gathered, processed, later act as tie points to the MASS stations. Apparently with this Malaysia will form a network to the globe. In this research the author will output the relative MASS stations coordinates and velocity estimates in International terrestrial reference frame (ITRF) 2000 since GPS data used are before the derivation of ITRF2005. At present the measures of quality for GPS derived coordinates given by commercial software packages tend to be unrealistic because unmodelled errors remain unaccounted for. The commercial software packages are either over-optimistic or conversely, therefore, have low fidelity. Thus

  9. A Real Time Differential GPS Tracking System for NASA Sounding Rockets

    NASA Technical Reports Server (NTRS)

    Bull, Barton; Bauer, Frank (Technical Monitor)

    2000-01-01

    Sounding rockets are suborbital launch vehicles capable of carrying scientific payloads to several hundred miles in altitude. These missions return a variety of scientific data including: chemical makeup and physical processes taking place in the atmosphere, natural radiation surrounding the Earth, data on the Sun, stars, galaxies and many other phenomena. In addition, sounding rockets provide a reasonably economical means of conducting engineering tests for instruments and devices to be used on satellites and other spacecraft prior to their use in these more expensive missions. Typically around thirty of these rockets are launched each year, from established ranges at Wallops Island, Virginia; Poker Flat Research Range, Alaska; White Sands Missile Range, New Mexico and from a number of ranges outside the United States. Many times launches are conducted from temporary launch ranges in remote parts of the world requiring considerable expense to transport and operate tracking radars. In order to support these missions, an inverse differential GPS system has been developed. The flight system consists of a small, inexpensive receiver, a preamplifier and a wrap-around antenna. A rugged, compact, portable ground station extracts GPS data from the raw payload telemetry stream, performs a real time differential solution and graphically displays the rocket's path relative to a predicted trajectory plot. In addition to generating a real time navigation solution, the system has been used for payload recovery, timing, data timetagging, precise tracking of multiple payloads and slaving of optical tracking systems for over the horizon acquisition. This paper discusses, in detail, the flight and ground hardware, as well as data processing and operational aspects of the system, and provides evidence of the system accuracy.

  10. Method and apparatus for relative navigation using reflected GPS signals

    NASA Technical Reports Server (NTRS)

    Cohen, Ian R. (Inventor); Boegner, Jr., Gregory J. (Inventor)

    2010-01-01

    A method and system to passively navigate an orbiting moving body towards an orbiting target using reflected GPS signals. A pair of antennas is employed to receive both direct signals from a plurality of GPS satellites and a second antenna to receive GPS signals reflected off an orbiting target. The direct and reflected signals are processed and compared to determine the relative distance and position of the orbiting moving body relative to the orbiting target.

  11. Superconductor Digital-RF Receiver Systems

    NASA Astrophysics Data System (ADS)

    Mukhanov, Oleg A.; Kirichenko, Dmitri; Vernik, Igor V.; Filippov, Timur V.; Kirichenko, Alexander; Webber, Robert; Dotsenko, Vladimir; Talalaevskii, Andrei; Tang, Jia Cao; Sahu, Anubhav; Shevchenko, Pavel; Miller, Robert; Kaplan, Steven B.; Sarwana, Saad; Gupta, Deepnarayan

    Digital superconductor electronics has been experiencing rapid maturation with the emergence of smaller-scale, lower-cost communications applications which became the major technology drivers. These applications are primarily in the area of wireless communications, radar, and surveillance as well as in imaging and sensor systems. In these areas, the fundamental advantages of superconductivity translate into system benefits through novel Digital-RF architectures with direct digitization of wide band, high frequency radio frequency (RF) signals. At the same time the availability of relatively small 4K cryocoolers has lowered the foremost market barrier for cryogenically-cooled digital electronic systems. Recently, we have achieved a major breakthrough in the development, demonstration, and successful delivery of the cryocooled superconductor digital-RF receivers directly digitizing signals in a broad range from kilohertz to gigahertz. These essentially hybrid-technology systems combine a variety of superconductor and semiconductor technologies packaged with two-stage commercial cryocoolers: cryogenic Nb mixed-signal and digital circuits based on Rapid Single Flux Quantum (RSFQ) technology, room-temperature amplifiers, FPGA processing and control circuitry. The demonstrated cryocooled digital-RF systems are the world's first and fastest directly digitizing receivers operating with live satellite signals in X-band and performing signal acquisition in HF to L-band at ˜30GHz clock frequencies.

  12. A simulation of GPS and differential GPS sensors

    NASA Technical Reports Server (NTRS)

    Rankin, James M.

    1993-01-01

    The Global Positioning System (GPS) is a revolutionary advance in navigation. Users can determine latitude, longitude, and altitude by receiving range information from at least four satellites. The statistical accuracy of the user's position is directly proportional to the statistical accuracy of the range measurement. Range errors are caused by clock errors, ephemeris errors, atmospheric delays, multipath errors, and receiver noise. Selective Availability, which the military uses to intentionally degrade accuracy for non-authorized users, is a major error source. The proportionality constant relating position errors to range errors is the Dilution of Precision (DOP) which is a function of the satellite geometry. Receivers separated by relatively short distances have the same satellite and atmospheric errors. Differential GPS (DGPS) removes these errors by transmitting pseudorange corrections from a fixed receiver to a mobile receiver. The corrected pseudorange at the moving receiver is now corrupted only by errors from the receiver clock, multipath, and measurement noise. This paper describes a software package that models position errors for various GPS and DGPS systems. The error model is used in the Real-Time Simulator and Cockpit Technology workstation simulations at NASA-LaRC. The GPS/DGPS sensor can simulate enroute navigation, instrument approaches, or on-airport navigation.

  13. The future of GPS-based electric power system measurements, operation and control

    SciTech Connect

    Rizy, D.T.; Wilson, R.E.; Martin, K.E.; Litzenberger, W.H.; Hauer, J.F.; Overholt, P.N.; Sobajic, D.J.

    1998-11-01

    Much of modern society is powered by inexpensive and reliable electricity delivered by a complex and elaborate electric power network. Electrical utilities are currently using the Global Positioning System-NAVSTAR (GPS) timekeeping to improve the network`s reliability. Currently, GPS synchronizes the clocks on dynamic recorders and aids in post-mortem analysis of network disturbances. Two major projects have demonstrated the use of GPS-synchronized power system measurements. In 1992, the Electric Power Research Institute`s (EPRI) sponsored Phase Measurements Project used a commercially available Phasor Measurements Unit (PMU) to collect GPS-synchronized measurements for analyzing power system problems. In 1995, Bonneville Power Administration (BPA) and Western Area Power Administration (WAPA) under DOE`s and EPRI`s sponsorship launched the Wide Area Measurements (WAMS) project. WAMS demonstrated GPS-synchronized measurements over a large area of their power networks and demonstrated the networking of GPS-based measurement systems in BPA and WAPA. The phasor measurement technology has also been used to conduct dynamic power system tests. During these tests, a large dynamic resistor was inserted to simulate a small power system disturbance.

  14. The Nuclear Detonation Detection System on the GPS satellites

    SciTech Connect

    Higbie, P.R.; Blocker, N.K.

    1993-07-27

    This article begins with a historical perspective of satellite usage in monitoring nuclear detonations. Current capabilities of the 24 GPS satellites in detecting the light, gamma rays, x-rays and neutrons from a nuclear explosion are described. In particular, an optical radiometer developed at Sandia National Laboratories is characterized. Operational information and calibration procedures are emphasized.

  15. An Integrated Navigation System using GPS Carrier Phase for Real-Time Airborne Synthetic Aperture Radar (SAR)

    SciTech Connect

    Fellerhoff, J. Rick; Kim, Theodore J.; Kohler, Stewart M.

    1999-06-24

    A Synthetic Aperture Radar (SAR) requires accu- rate measurement of the motion of the imaging plat- form to produce well-focused images with minimal absolute position error. The motion measurement (MoMeas) system consists of a inertial measurement unit (IMU) and a P-code GPS receiver that outputs corrected ephemeris, L1 & L2 pseudoranges, and L1 & L2 carrier phase measurements. The unknown initial carrier phase biases to the GPS satellites are modeled as states in an extended Kalman filter and the resulting integrated navigation solution has po- sition errors that change slowly with time. Position error drifts less than 1- cm/sec have been measured from the SAR imagery for various length apertures.

  16. GPS Radio Occultation as Part of the Global Observing System for Atmosphere

    NASA Technical Reports Server (NTRS)

    Mannucci, Anthony J.; Ao, C. O.; Iijima, B. A.; Wilson, B. D.; Yunck, T. P.; Kursinski, E. R.

    2008-01-01

    Topics include: The Measurement (Physical retrievals based on time standards), GPS Retrieval Products, Retrievals and Radiances: CLARREO Mission, GPS RO and AIRS, GPS RO and Microwave, GPS RO and Radiosondes, GPS/GNSS Science, and Conclusions.

  17. Receivers

    NASA Astrophysics Data System (ADS)

    Donnelly, H.

    1983-07-01

    Before discussing Deep Space Network receivers, a brief description of the functions of receivers and how they interface with other elements of the Network is presented. Different types of receivers are used in the Network for various purposes. The principal receiver type is used for telemetry and tracking. This receiver provides the capability, with other elements of the Network, to track the space probe utilizing Doppler and range measurements, and to receive telemetry, including both scientific data from the onboard experiments and engineering data pertaining to the health of the probe. Another type of receiver is used for radio science applications. This receiver measures phase perturbations on the carrier signal to obtain information on the composition of solar and planetary atmospheres and interplanetary space. A third type of receiver utilizes very long baseline interferometry (VLBI) techniques for both radio science and spacecraft navigation data. Only the telemetry receiver is described in detail in this document. The integration of the Receiver-Exciter subsystem with other portions of the Deep Space Network is described.

  18. Receivers

    NASA Technical Reports Server (NTRS)

    Donnelly, H.

    1983-01-01

    Before discussing Deep Space Network receivers, a brief description of the functions of receivers and how they interface with other elements of the Network is presented. Different types of receivers are used in the Network for various purposes. The principal receiver type is used for telemetry and tracking. This receiver provides the capability, with other elements of the Network, to track the space probe utilizing Doppler and range measurements, and to receive telemetry, including both scientific data from the onboard experiments and engineering data pertaining to the health of the probe. Another type of receiver is used for radio science applications. This receiver measures phase perturbations on the carrier signal to obtain information on the composition of solar and planetary atmospheres and interplanetary space. A third type of receiver utilizes very long baseline interferometry (VLBI) techniques for both radio science and spacecraft navigation data. Only the telemetry receiver is described in detail in this document. The integration of the Receiver-Exciter subsystem with other portions of the Deep Space Network is described.

  19. Application of new GPS aircraft control/display system to topographic mapping of the Greenland ice cap

    SciTech Connect

    Wright, C.W.; Swift, R.N.

    1996-10-01

    NASA has completed an accurate baseline map of the elevation of the Greenland ice sheet using a scanning airborne lidar in combination with differential kinematic Global Positioning System (GPS) techniques. The present plan is to reoccupy these survey lines which are spread over the major regions of the ice sheet beginning in 1997. The results are expected to provide a quantitative answer on how the ice sheet is responding to regional climatic changes. Navigation to within +-100 m of the desired track over lengths of up to 1,000 km are a requirement for the success of the program. To meet this navigational requirement, NASA developed the GPS Flight Management System (GFMS). GFMS is a PC based system that uses the real-time position update from a single GPS receiver located on the aircraft to calculate a cross-track error and generates aircraft steering commands which are converted into analog Instrument Landing System (OM) signals using an RF generator. TU GFMS also updates a cockpit display. 4 refs., 6 figs.

  20. Enhancing Positioning Accuracy in Urban Terrain by Fusing Data from a GPS Receiver, Inertial Sensors, Stereo-Camera and Digital Maps for Pedestrian Navigation

    PubMed Central

    Przemyslaw, Baranski; Pawel, Strumillo

    2012-01-01

    The paper presents an algorithm for estimating a pedestrian location in an urban environment. The algorithm is based on the particle filter and uses different data sources: a GPS receiver, inertial sensors, probability maps and a stereo camera. Inertial sensors are used to estimate a relative displacement of a pedestrian. A gyroscope estimates a change in the heading direction. An accelerometer is used to count a pedestrian's steps and their lengths. The so-called probability maps help to limit GPS inaccuracy by imposing constraints on pedestrian kinematics, e.g., it is assumed that a pedestrian cannot cross buildings, fences etc. This limits position inaccuracy to ca. 10 m. Incorporation of depth estimates derived from a stereo camera that are compared to the 3D model of an environment has enabled further reduction of positioning errors. As a result, for 90% of the time, the algorithm is able to estimate a pedestrian location with an error smaller than 2 m, compared to an error of 6.5 m for a navigation based solely on GPS. PMID:22969321

  1. A GPS Backpack System for Mapping Soil and Crop Parameters in Agricultural Fields

    NASA Astrophysics Data System (ADS)

    Stafford, J. V.; Lebars, J. M.

    Farmers are having to gather increasing amounts of data on their soils and crops. Precision agriculture metre-by-metre is based on a knowledge of the spatial variation of soil and crop parameters across a field. The data has to be spatially located and GPS is an effective way of doing this. A backpack data logging system with GPS position tagging is described which has been designed to aid a fanner in the manual collection of data.

  2. A GPS-based system for recording the flight paths of birds

    NASA Astrophysics Data System (ADS)

    von Hünerbein, K.; Hamann, H.-J.; Rüter, E.; Wiltschko, W.

    The GPS recorder consists of a GPS receiver board, a logging facility, an antenna, a power supply, a DC-DC converter and a casing. Currently, it has a weight of 33g. The recorder works reliably with a sampling rate of 1/s and with an operation time of about 3h, providing time-indexed data on geographic positions and ground speed. The data are downloaded when the animal is recaptured. Prototypes were tested on homing pigeons. The records of complete flight paths with surprising details illustrate the potential of this new method that can be used on a variety of medium-sized and large vertebrates.

  3. GPS Metric Tracking Unit

    NASA Technical Reports Server (NTRS)

    2008-01-01

    As Global Positioning Satellite (GPS) applications become more prevalent for land- and air-based vehicles, GPS applications for space vehicles will also increase. The Applied Technology Directorate of Kennedy Space Center (KSC) has developed a lightweight, low-cost GPS Metric Tracking Unit (GMTU), the first of two steps in developing a lightweight, low-cost Space-Based Tracking and Command Subsystem (STACS) designed to meet Range Safety's link margin and latency requirements for vehicle command and telemetry data. The goals of STACS are to improve Range Safety operations and expand tracking capabilities for space vehicles. STACS will track the vehicle, receive commands, and send telemetry data through the space-based asset, which will dramatically reduce dependence on ground-based assets. The other step was the Low-Cost Tracking and Data Relay Satellite System (TDRSS) Transceiver (LCT2), developed by the Wallops Flight Facility (WFF), which allows the vehicle to communicate with a geosynchronous relay satellite. Although the GMTU and LCT2 were independently implemented and tested, the design collaboration of KSC and WFF engineers allowed GMTU and LCT2 to be integrated into one enclosure, leading to the final STACS. In operation, GMTU needs only a radio frequency (RF) input from a GPS antenna and outputs position and velocity data to the vehicle through a serial or pulse code modulation (PCM) interface. GMTU includes one commercial GPS receiver board and a custom board, the Command and Telemetry Processor (CTP) developed by KSC. The CTP design is based on a field-programmable gate array (FPGA) with embedded processors to support GPS functions.

  4. BDS/GPS Dual Systems Positioning Based on the Modified SR-UKF Algorithm.

    PubMed

    Kong, JaeHyok; Mao, Xuchu; Li, Shaoyuan

    2016-01-01

    The Global Navigation Satellite System can provide all-day three-dimensional position and speed information. Currently, only using the single navigation system cannot satisfy the requirements of the system's reliability and integrity. In order to improve the reliability and stability of the satellite navigation system, the positioning method by BDS and GPS navigation system is presented, the measurement model and the state model are described. Furthermore, the modified square-root Unscented Kalman Filter (SR-UKF) algorithm is employed in BDS and GPS conditions, and analysis of single system/multi-system positioning has been carried out, respectively. The experimental results are compared with the traditional estimation results, which show that the proposed method can perform highly-precise positioning. Especially when the number of satellites is not adequate enough, the proposed method combine BDS and GPS systems to achieve a higher positioning precision. PMID:27153068

  5. Gravity field error analysis - Applications of Global Positioning System receivers and gradiometers on low orbiting platforms

    NASA Technical Reports Server (NTRS)

    Schrama, Ernst J. O.

    1991-01-01

    The concept of a Global Positioning System (GPS) receiver as a tracking facility and a gradiometer as a separate instrument on a low-orbiting platform offers a unique tool to map the earth's gravitational field with unprecedented accuracies. The former technique allows determination of the spacecraft's ephemeris at any epoch to within 3-10 cm, the latter permits the measurement of the tensor of second order derivatives of the gravity field to within 0.01 to 0.0001 Eotvos units depending on the type of gradiometer. First, a variety of error sources in gradiometry where emphasis is placed on the rotational problem pursuing as well a static as a dynamic approach is described. Next, an analytical technique is described and applied for an error analysis of gravity field parameters from gradiometer and GPS observation types. Results are discussed for various configurations proposed on Topex/Poseidon, Gravity Probe-B, and Aristoteles, indicating that GPS only solutions may be computed up to degree and order 35, 55, and 85, respectively, whereas a combined GPS/gradiometer experiment on Aristoteles may result in an acceptable solution up to degree and order 240.

  6. BDS/GPS Dual Systems Positioning Based on the Modified SR-UKF Algorithm

    PubMed Central

    Kong, JaeHyok; Mao, Xuchu; Li, Shaoyuan

    2016-01-01

    The Global Navigation Satellite System can provide all-day three-dimensional position and speed information. Currently, only using the single navigation system cannot satisfy the requirements of the system’s reliability and integrity. In order to improve the reliability and stability of the satellite navigation system, the positioning method by BDS and GPS navigation system is presented, the measurement model and the state model are described. Furthermore, the modified square-root Unscented Kalman Filter (SR-UKF) algorithm is employed in BDS and GPS conditions, and analysis of single system/multi-system positioning has been carried out, respectively. The experimental results are compared with the traditional estimation results, which show that the proposed method can perform highly-precise positioning. Especially when the number of satellites is not adequate enough, the proposed method combine BDS and GPS systems to achieve a higher positioning precision. PMID:27153068

  7. Application of GPS tracking techniques to orbit determination for TDRS

    NASA Technical Reports Server (NTRS)

    Haines, B. J.; Lichten, S. M.; Malla, R. P.; Wu, S. C.

    1993-01-01

    In this paper, we evaluate two fundamentally different approaches to TDRS orbit determination utilizing Global Positioning System (GPS) technology and GPS-related techniques. In the first, a GPS flight receiver is deployed on the TDRSS spacecraft. The TDRS ephemerides are determined using direct ranging to the GPS spacecraft, and no ground network is required. In the second approach, the TDRSS spacecraft broadcast a suitable beacon signal, permitting the simultaneous tracking of GPS and TDRSS satellites from a small ground network. Both strategies can be designed to meet future operational requirements for TDRS-2 orbit determination.

  8. Development of the visually impaired person guidance system using GPS.

    PubMed

    Soeda, Koji; Aoki, Shingo; Yanashima, Kenji; Magatani, Kazushige

    2004-01-01

    Most of the visually impaired are able to walk independently, if they have the mental map of their walking area. However, in their unknown area, they cannot walk alone and they need a guide dog or help of others for walking. And not only a supporter of the visually impaired but a visually impaired person receives stress while walking. More over in Japan, there are about 300,000 visually impaired persons, and are about 900 guide dogs. These number of guide dogs are too few. Therefore, an auto navigation system for the visually impaired is required in Japan. Our objective is the development of the auto navigation system for the visually impaired. This navigation system obtains the position of an user (visually impaired user) by DGPS. From the digital map data base in our system and the position of an use are analyzed, and suitable route to the destination is calculated, and then our system guides the way to the destination to the user. In this paper, we'd like to report about our new navigation system for the visually impaired and report some experimental results of our system. From these results, we think our system will be a powerful for the visually impaired. PMID:17271403

  9. The Accuracy of a Simple, Low-Cost GPS Data Logger/Receiver to Study Outdoor Human Walking in View of Health and Clinical Studies

    PubMed Central

    Noury-Desvaux, Bénédicte; Abraham, Pierre; Mahé, Guillaume; Sauvaget, Thomas; Leftheriotis, Georges; Le Faucheur, Alexis

    2011-01-01

    Introduction Accurate and objective measurements of physical activity and lower-extremity function are important in health and disease monitoring, particularly given the current epidemic of chronic diseases and their related functional impairment. Purpose The aim of the present study was to determine the accuracy of a handy (lightweight, small, only one stop/start button) and low-cost (∼$75 with its external antenna) Global Positioning System (GPS) data logger/receiver (the DG100) as a tool to study outdoor human walking in perspective of health and clinical research studies. Methods. Healthy subjects performed two experiments that consisted of different prescribed outdoor walking protocols. Experiment 1. We studied the accuracy of the DG100 for detecting bouts of walking and resting. Experiment 2. We studied the accuracy of the DG100 for estimating distances and speeds of walking. Results Experiment 1. The performance in the detection of bouts, expressed as the percentage of walking and resting bouts that were correctly detected, was 92.4% [95% Confidence Interval: 90.6–94.3]. Experiment 2. The coefficients of variation [95% Confidence Interval] for the accuracy of estimating the distances and speeds of walking were low: 3.1% [2.9–3.3] and 2.8% [2.6–3.1], respectively. Conclusion The DG100 produces acceptable accuracy both in detecting bouts of walking and resting and in estimating distances and speeds of walking during the detected walking bouts. However, before we can confirm that the DG100 can be used to study walking with respect to health and clinical studies, the inter- and intra-DG100 variability should be studied. Trial Registration ClinicalTrials.gov NCT00485147 PMID:21931593

  10. 76 FR 50808 - Airborne Supplemental Navigation Equipment Using the Global Positioning System (GPS)

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-08-16

    ... cancel TSO-C129a, Airborne Supplemental Navigation Equipment Using the Global Positioning System (GPS... Global Positioning System Equipment Using Aircraft-Based Augmentation; an updated minimum performance... system (TSO-C145c, Airborne Navigation Sensors Using the Global Positioning System Augmented by...

  11. Adaptive Resampling Particle Filters for GPS Carrier-Phase Navigation and Collision Avoidance System

    NASA Astrophysics Data System (ADS)

    Hwang, Soon Sik

    This dissertation addresses three problems: 1) adaptive resampling technique (ART) for Particle Filters, 2) precise relative positioning using Global Positioning System (GPS) Carrier-Phase (CP) measurements applied to nonlinear integer resolution problem for GPS CP navigation using Particle Filters, and 3) collision detection system based on GPS CP broadcasts. First, Monte Carlo filters, called Particle Filters (PF), are widely used where the system is non-linear and non-Gaussian. In real-time applications, their estimation accuracies and efficiencies are significantly affected by the number of particles and the scheduling of relocating weights and samples, the so-called resampling step. In this dissertation, the appropriate number of particles is estimated adaptively such that the error of the sample mean and variance stay in bounds. These bounds are given by the confidence interval of a normal probability distribution for a multi-variate state. Two required number of samples maintaining the mean and variance error within the bounds are derived. The time of resampling is determined when the required sample number for the variance error crosses the required sample number for the mean error. Second, the PF using GPS CP measurements with adaptive resampling is applied to precise relative navigation between two GPS antennas. In order to make use of CP measurements for navigation, the unknown number of cycles between GPS antennas, the so called integer ambiguity, should be resolved. The PF is applied to this integer ambiguity resolution problem where the relative navigation states estimation involves nonlinear observations and nonlinear dynamics equation. Using the PF, the probability density function of the states is estimated by sampling from the position and velocity space and the integer ambiguities are resolved without using the usual hypothesis tests to search for the integer ambiguity. The ART manages the number of position samples and the frequency of the

  12. A summary of the GPS system performance for STARS Mission 3

    SciTech Connect

    Creel, E.E.

    1997-08-01

    This paper describes the performance of the GPS system on the most recent flight of the STARS missile, STARS Mission 3 (M3). This mission was conducted under the Ballistic Missile Defense Organization`s (BMDO`s) Consolidated Targets Program. The United States Army Space and Strategic Defense Command (USASSDC) is the executing agent for this mission and the Department of Energy`s (DOE`s) Sandia National Laboratories (SNL) is the vehicle developer and integrator. The M3 flight, dually designated as the MSX Dedicated Targets II (MDT-II) mission occurred on August 31, 1996. This mission was conducted for the specific purpose of providing targets for viewing by the MSX satellite. STARS M3 was the first STARS flight to use GPS-derived data for missile guidance, and proved to be instrumental in the procurement of a wealth of experimental data which is still undergoing analysis by numerous scientific agencies within the BMDO complex. GPS accuracy was required for this mission because of the prescribed targeting requirements for the MDT-II payload deliveries with respect to the MSX satellite flight path. During the flight test real time GPS-derived state vector data was also used to generate pointing angles for various down range sensors involved in the experiment. Background information describing the STARS missile, GPS subsystem architecture, and the GPS Kalman filter design is presented first, followed by a discussion of the telemetry data records obtained from this flight with interpretations and conclusions.

  13. Global Positioning System (GPS) Precipitable Water in Forecasting Lightning at Spaceport Canaveral

    NASA Technical Reports Server (NTRS)

    Kehrer, Kristen C.; Graf, Brian; Roeder, William

    2006-01-01

    This paper evaluates the use of precipitable water (PW) from Global Positioning System (GPS) in lightning prediction. Additional independent verification of an earlier model is performed. This earlier model used binary logistic regression with the following four predictor variables optimally selected from a candidate list of 23 candidate predictors: the current precipitable water value for a given time of the day, the change in GPS-PW over the past 9 hours, the KIndex, and the electric field mill value. This earlier model was not optimized for any specific forecast interval, but showed promise for 6 hour and 1.5 hour forecasts. Two new models were developed and verified. These new models were optimized for two operationally significant forecast intervals. The first model was optimized for the 0.5 hour lightning advisories issued by the 45th Weather Squadron. An additional 1.5 hours was allowed for sensor dwell, communication, calculation, analysis, and advisory decision by the forecaster. Therefore the 0.5 hour advisory model became a 2 hour forecast model for lightning within the 45th Weather Squadron advisory areas. The second model was optimized for major ground processing operations supported by the 45th Weather Squadron, which can require lightning forecasts with a lead-time of up to 7.5 hours. Using the same 1.5 lag as in the other new model, this became a 9 hour forecast model for lightning within 37 km (20 NM)) of the 45th Weather Squadron advisory areas. The two new models were built using binary logistic regression from a list of 26 candidate predictor variables: the current GPS-PW value, the change of GPS-PW over 0.5 hour increments from 0.5 to 12 hours, and the K-index. The new 2 hour model found the following for predictors to be statistically significant, listed in decreasing order of contribution to the forecast: the 0.5 hour change in GPS-PW, the 7.5 hour change in GPS-PW, the current GPS-PW value, and the KIndex. The new 9 hour forecast model found

  14. GPS antenna designs

    NASA Technical Reports Server (NTRS)

    Laube, Samuel J. P.

    1987-01-01

    Application of the current GPS NAVSTAR system to civilian service requires that a right hand, circularly polarized, -160 dBW spread spectrum signal be received from an orbiting satellite, where the antenna environment is also moving. This presents a design challenge when inexpensive antennas are desired. The intent of this survey is to provide information on the antennas mentioned and to construct and test prototypes to determine whether the choice made by the industry, the quadrifilar helix, is the best. The helix antenna is currently the low cost standard for GPS. Prototype versions were constructed using 12 gauge wire and subminiature coaxial hardline. The constructed antennas were tested using a signal generator and a reference turnstile. A spectrum analyzer was used to measure the level of the received signal.

  15. GPS antenna designs

    NASA Astrophysics Data System (ADS)

    Laube, Samuel J. P.

    1987-05-01

    Application of the current GPS NAVSTAR system to civilian service requires that a right hand, circularly polarized, -160 dBW spread spectrum signal be received from an orbiting satellite, where the antenna environment is also moving. This presents a design challenge when inexpensive antennas are desired. The intent of this survey is to provide information on the antennas mentioned and to construct and test prototypes to determine whether the choice made by the industry, the quadrifilar helix, is the best. The helix antenna is currently the low cost standard for GPS. Prototype versions were constructed using 12 gauge wire and subminiature coaxial hardline. The constructed antennas were tested using a signal generator and a reference turnstile. A spectrum analyzer was used to measure the level of the received signal.

  16. Supporting EarthScope Cyber-Infrastructure with a Modern GPS Science Data System

    NASA Astrophysics Data System (ADS)

    Webb, F. H.; Bock, Y.; Kedar, S.; Jamason, P.; Fang, P.; Dong, D.; Owen, S. E.; Prawirodirjo, L.; Squibb, M.

    2008-12-01

    Building on NASA's investment in the measurement of crustal deformation from continuous GPS, we are developing and implementing a Science Data System (SDS) that will provide mature, long-term Earth Science Data Records (ESDR's). This effort supports NASA's Earth Surface and Interiors (ESI) focus area and provide NASA's component to the EarthScope PBO. This multi-year development is sponsored by NASA's Making Earth System data records for Use in Research Environments (MEaSUREs) program. The SDS integrates the generation of ESDRs with data analysis and exploration, product generation, and modeling tools based on daily GPS data that include GPS networks in western North America and a component of NASA's Global GPS Network (GGN) for terrestrial reference frame definition. The system is expandable to multiple regional and global networks. The SDS builds upon mature data production, exploration, and analysis algorithms developed under NASA's REASoN, ACCESS, and SENH programs. This SDS provides access to positions, time series, velocity fields, and strain measurements derived from continuous GPS data obtained at tracking stations in both the Plate Boundary Observatory and other regional Western North America GPS networks, dating back to 1995. The SDS leverages the IT and Web Services developments carried out under the SCIGN/REASoN and ACCESS projects, which have streamlined access to data products for researchers and modelers, and which have created a prototype an on-the-fly interactive research environment through a modern data portal, GPS Explorer. This IT system has been designed using modern IT tools and principles in order to be extensible to any geographic location, scale, natural hazard, and combination of geophysical sensor and related data. We have built upon open GIS standards, particularly those of the OGC, and have used the principles of Web Service-based Service Oriented Architectures to provide scalability and extensibility to new services and capabilities.

  17. Wireless GPS-based phase-locked synchronization system for outdoor environment.

    PubMed

    Meyer, Frédéric; Bahr, Alexander; Lochmatter, Thomas; Borrani, Fabio

    2012-01-01

    Synchronization of data coming from different sources is of high importance in biomechanics to ensure reliable analyses. This synchronization can either be performed through hardware to obtain perfect matching of data, or post-processed digitally. Hardware synchronization can be achieved using trigger cables connecting different devices in many situations; however, this is often impractical, and sometimes impossible in outdoors situations. The aim of this paper is to describe a wireless system for outdoor use, allowing synchronization of different types of - potentially embedded and moving - devices. In this system, each synchronization device is composed of: (i) a GPS receiver (used as time reference), (ii) a radio transmitter, and (iii) a microcontroller. These components are used to provide synchronized trigger signals at the desired frequency to the measurement device connected. The synchronization devices communicate wirelessly, are very lightweight, battery-operated and thus very easy to set up. They are adaptable to every measurement device equipped with either trigger input or recording channel. The accuracy of the system was validated using an oscilloscope. The mean synchronization error was found to be 0.39 μs and pulses are generated with an accuracy of <2 μs. The system provides synchronization accuracy about two orders of magnitude better than commonly used post-processing methods, and does not suffer from any drift in trigger generation. PMID:22001610

  18. Wakeshield WSF-02 GPS Experiment

    NASA Technical Reports Server (NTRS)

    Schutz, B. E.; Abusali, P. A. M.; Schroeder, Christine; Tapley, Byron; Exner, Michael; Mccloskey, rick; Carpenter, Russell; Cooke, Michael; Mcdonald, samantha; Combs, Nick; Duncan, Courtney; Dunn, Charles; Meehan, Tom

    1995-01-01

    Shuttle mission STS-69 was launched on September 7, 1995, 10:09 CDT, carrying the Wake Shield Facility (WSF-02). The WSF-02 spacecraft included a set of payloads provided by the Texas Space Grant Consortium, known as TexasSat. One of the TexasSat payloads was a GPS TurboRogue receiver loaned by the University Corporation for Atmospheric Research. On September 11, the WSF-02 was unberthed from the Endeavour payload bay using the remote manipulator system. The GPS receiver was powered on prior to release and the WSF-02 remained in free-flight for three days before being retrieved on September 14. All WSF-02 GPS data, which includes dual frequency pseudorange and carrier phase, were stored in an on-board recorder for post-flight analysis, but "snap- shots" of data were transmitted for 2-3 minutes at intervals of several hours, when permitted by the telemetry band- widdl The GPS experiment goals were: (1) an evaluation of precision orbit determination in a low altitude environment (400 km) where perturbations due to atmospheric drag and the Earth's gravity field are more pronounced than for higher altitude satellites with high precision orbit requirements, such as TOPEX/POSEIDON; (2) an assessment of relative positioning using the WSF GPS receiver and the Endeavour Collins receiver; and (3) determination of atmospheric temperature profiles using GPS signals passing through the atmosphere. Analysis of snap-shot telemetry data indicate that 24 hours of continuous data were stored on board, which includes high rate (50 Hz) data for atmosphere temperature profiles. Examination of the limited number of real-time navigation solutions show that at least 7 GPS satellites were tracked simultaneously and the on-board clock corrections were at the microsec level, as expected. Furthermore, a dynamical consistency test provided a further validation of the on-board navigation solutions. Complete analysis will be conducted in post-flight using the data recorded on-board.

  19. Performance analysis of an integrated GPS/inertial attitude determination system. M.S. Thesis - MIT

    NASA Technical Reports Server (NTRS)

    Sullivan, Wendy I.

    1994-01-01

    The performance of an integrated GPS/inertial attitude determination system is investigated using a linear covariance analysis. The principles of GPS interferometry are reviewed, and the major error sources of both interferometers and gyroscopes are discussed and modeled. A new figure of merit, attitude dilution of precision (ADOP), is defined for two possible GPS attitude determination methods, namely single difference and double difference interferometry. Based on this figure of merit, a satellite selection scheme is proposed. The performance of the integrated GPS/inertial attitude determination system is determined using a linear covariance analysis. Based on this analysis, it is concluded that the baseline errors (i.e., knowledge of the GPS interferometer baseline relative to the vehicle coordinate system) are the limiting factor in system performance. By reducing baseline errors, it should be possible to use lower quality gyroscopes without significantly reducing performance. For the cases considered, single difference interferometry is only marginally better than double difference interferometry. Finally, the performance of the system is found to be relatively insensitive to the satellite selection technique.

  20. Solar receiver performance of point focusing collector system

    NASA Technical Reports Server (NTRS)

    Wu, Y. C.; Wen, L. C.

    1978-01-01

    The solar receiver performance of cavity receivers and external receivers used in dispersed solar power systems was evaluated for the temperature range 300-1300 C. Several parameters of receiver and concentrator are examined. It was found that cavity receivers are generally more efficient than external receivers, especially at high temperatures which require a large heat transfer area. The effects of variation in the ratio of receiver area to aperture area are considered.

  1. Intercontinental time and frequency transfer using a global positioning system timing receiver

    NASA Technical Reports Server (NTRS)

    Clements, P. A.

    1983-01-01

    The Deep Space Network (DSN) has a requirement to maintain knowledge of the frequency offset between DSN stations within 3 x 10 to the -13th power and time offset within 10 microseconds. It is further anticipated that in the 1987-1990 era the requirement for knowledge of time offset between DSN stations will be less than 10 nanoseconds. The Jet Propulsion Laboratory (JPL) is using the Global Positioning System (GPS) Space Vehicles, as a development project, to transfer time and frequency over intercontinental distances between stations of the DSN and between the DSN and other agencies. JPL has installed GPS timing receivers at its tracking station near Barstow, California and at its tracking station near Madrid, Spain. The details of the experiment and the data are reported. There is a discussion of the ultimate capabilities of these techniques for meeting the functional requirements of the DSN.

  2. Intercontinental time and frequency transfer using a global positioning system timing receiver

    NASA Technical Reports Server (NTRS)

    Clements, P. A.

    1983-01-01

    The DSN has a requirement to maintain knowledge of the frequency offset between DSN stations with 3 x 10 to the minus 13th power and time offset within 10 microseconds. It is further anticipated that in the 1987-1990 era the requirement for knowledge of time offset between DSN stations will be less than 10 nanoseconds. JPL is using the Global Positioning System (GPS) Space Vehicles, as a development project, to transfer time and frequency over intercontinental distances between stations of the DSN and between the DSN and other agencies. JPL has installed GPS timing receivers at its tracking station near Barstow, California, and at its tracking station near Madrid, Spain. The details of the experiment and the data are reported. There is a discussion of the ultimate capabilities of these techniques for meeting the functional requirements of the DSN.

  3. GPS-based navigation for space applications

    NASA Astrophysics Data System (ADS)

    Champetier, C.; Duhamel, T.; Frezet, M.

    1995-03-01

    We present in this paper a survey of the applications of the GPS (global positioning system) system for spacecraft navigation. The use of the GPS techniques for space missions is a striking example of dual-use of military technology; it can bring vast improvements in performances and, in some cases, for a reduced cost. We only deal in this paper with the functional aspects and performances of GPS uses without addressing the issues of hardware implementation where current developments are leading to an increased miniaturization of the GPS receiver hardware. We start this paper with a general overview of the GPS system and its various uses for space missions. We then focus on four areas where MATRA MARCONI Space has conducted detailed analyses of performances: autonomous navigation for geostationary spacecraft, relative navigation for space rendezvous, differential navigation for landing vehicles, absolute navigation for launchers and reentry vehicles.

  4. Application of GPS attitude determination to gravity gradient stabilized spacecraft

    NASA Technical Reports Server (NTRS)

    Lightsey, E. G.; Cohen, Clark E.; Parkinson, Bradford W.

    1993-01-01

    Recent advances in the Global Positioning System (GPS) technology have initiated a new era in aerospace navigation and control. GPS receivers have become increasingly compact and affordable, and new developments have made attitude determination using subcentimeter positioning among two or more antennas feasible for real-time applications. GPS-based attitude control systems will become highly portable packages which provide time, navigation, and attitude information of sufficient accuracy for many aerospace needs. A typical spacecraft application of GPS attitude determination is a gravity gradient stabilized satellite in low Earth orbit that employs a GPS receiver and four body mounted patch antennas. The coupled, linearized equations of motion enable complete position and attitude information to be extracted from only two antennas. A discussion of the various error sources for spaceborne GPS attitude measurement systems is included. Attitude determination of better than 0.3 degrees is possible for 1 meter antenna separation. Suggestions are provided to improve the accuracy of the attitude solution.

  5. Receiver Design, Performance Analysis, and Evaluation for Space-Borne Laser Altimeters and Space-to-Space Laser Ranging Systems

    NASA Technical Reports Server (NTRS)

    Davidson, Frederic M.; Sun, Xiaoli; Field, Christopher T.

    1996-01-01

    This progress report consists of two separate reports. The first one describes our work on the use of variable gain amplifiers to increase the receiver dynamic range of space borne laser altimeters such as NASA's Geoscience Laser Altimeter Systems (GLAS). The requirement of the receiver dynamic range was first calculated. A breadboard variable gain amplifier circuit was made and the performance was fully characterized. The circuit will also be tested in flight on board the Shuttle Laser Altimeter (SLA-02) next year. The second report describes our research on the master clock oscillator frequency calibration for space borne laser altimeter systems using global positioning system (GPS) receivers.

  6. Development of a GPS-aided motion measurement, pointing, and stabilization system for a Synthetic Aperture Radar. [Global Positioning System (GPS)

    SciTech Connect

    Fellerhoff, J.R.; Kohler, S.M.

    1991-01-01

    An advanced Synthetic Aperture Radar Motion Compensation System has been developed by Sandia National Laboratories (SNL). The system includes a miniaturized high accuracy ring laser gyro inertial measurement unit, a three axis gimbal pointing and stabilization assembly, a differential Global Positioning System (GPS) navigation aiding system, and a pilot guidance system. The system provides several improvements over previous SNL motion compensation systems and is capable of antenna stabilization to less than 0.01 degrees RMS and absolute position measurement to less than 5.0 meters RMS. These accuracies have been demonstrated in recent flight testing aboard a DHC-6-300 Twin Otter'' aircraft.

  7. On Fast Post-Processing of Global Positioning System Simulator Truth Data and Receiver Measurements and Solutions Data

    NASA Technical Reports Server (NTRS)

    Kizhner, Semion; Day, John H. (Technical Monitor)

    2000-01-01

    Post-Processing of data related to a Global Positioning System (GPS) simulation is an important activity in qualification of a GPS receiver for space flight. Because a GPS simulator is a critical resource it is desirable to move off the pertinent simulation data from the simulator as soon as a test is completed. The simulator data files are usually moved to a Personal Computer (PC), where the post-processing of the receiver logged measurements and solutions data and simulated data is performed. Typically post-processing is accomplished using PC-based commercial software languages and tools. Because of commercial software systems generality their general-purpose functions are notoriously slow and more than often are the bottleneck problem even for short duration experiments. For example, it may take 8 hours to post-process data from a 6-hour simulation. There is a need to do post-processing faster, especially in order to use the previous test results as feedback for a next simulation setup. This paper demonstrates that a fast software linear interpolation algorithm is applicable to a large class of engineering problems, like GPS simulation data post-processing, where computational time is a critical resource and is one of the most important considerations. An approach is developed that allows to speed-up post-processing by an order of magnitude. It is based on improving the post-processing bottleneck interpolation algorithm using apriori information that is specific to the GPS simulation application. The presented post-processing scheme was used in support of a few successful space flight missions carrying GPS receivers. A future approach to solving the post-processing performance problem using Field Programmable Gate Array (FPGA) technology is described.

  8. Phase Correction for GPS Antenna with Nonunique Phase Center

    NASA Technical Reports Server (NTRS)

    Fink, Patrick W.; Dobbins, Justin

    2005-01-01

    A method of determining the position and attitude of a body equipped with a Global Positioning System (GPS) receiver includes an accounting for the location of the nonunique phase center of a distributed or wraparound GPS antenna. The method applies, more specifically, to the case in which (1) the GPS receiver utilizes measurements of the phases of GPS carrier signals in its position and attitude computations and (2) the body is axisymmetric (e.g., spherical or round cylindrical) and wrapped at its equator with a single- or multiple-element antenna, the radiation pattern of which is also axisymmetric with the same axis of symmetry as that of the body.

  9. GPS-INS-STAR - A navigation system for the era of space autonomy

    NASA Astrophysics Data System (ADS)

    Tanabe, Toru; Kitamura, Toshiaki; Ikeuchi, Masayuki; Tanaka, Toshiyuki; Akasaka, Akira

    Experimental validation of the GPS-INS-STAR hybrid navigation system concept is performed. First, an INS-STAR hybrid navigation system is constructed on the 3-axis motion table to verify the performance of its attitude loop. A GPS-INS hybrid navigation system is then installed on a car, and its translational performance is evaluated. Each result of the experiments is verified by theoretical analysis, and its feasibility for space application is evaluated. Through the experiments, the concept of the autonomous hybrid navigation is validated, and its potential in space autonomy is indicated.

  10. Validating the airborne and ground based components of a differential GPS system

    NASA Technical Reports Server (NTRS)

    Edwards, F. G.; Hegarty, D. M.; Turner, R. N.; Van Graas, F.; Sharma, S.

    1988-01-01

    A differential GPS mechanization of an external data link concept under development at NASA Ames Research Center is discussed. The system is intended to evaluate the use of differential GPS to support helicopter approach operation. Analytical techniques for static testing and evaluation of the system hardware and software performance in real time are described. Several techniques that have been used to detect and rectify a specific problem encountered during the tests are dicussed. An example of flight test results using the validated system is provided.

  11. Advancing Technology: GPS and GIS Outreach Training for Agricultural Producers

    ERIC Educational Resources Information Center

    Flynn, Allison; Arnold, Shannon

    2010-01-01

    The use of the Global Positioning System (GPS) and Global Information Systems (GIS) has made significant impacts on agricultural production practices. However, constant changes in the technologies require continuing educational updates. The outreach program described here introduces the operation, use, and applications of GPS receivers and GIS…

  12. 75 FR 61818 - Eighty-Third Meeting: RTCA Special Committee 159: Global Positioning System (GPS).

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-10-06

    ... 7, GPS/Antennas, ARINC Room. Friday, October 29 Plenary Session--See Agenda Below Agenda--Plenary...-4) GPS/Airport Surface Surveillance (WG-5) GPS/Interference (WG-6) GPS/Antennas (WG-7) Review...

  13. The use of GPS for automatic vehicle location and fleet management - A reliable and economic system for the 90's

    NASA Astrophysics Data System (ADS)

    Denaro, Robert P.

    1991-01-01

    This paper offers an approach to an integrated automatic vehicle location (AVL) system that integrates GPS with communications links, auxiliary dead reckoning sensors, and modern workstation implementation of a control and location monitoring center. The actual implementation of this AVL system in a municipal bus operation is described, along with other fleet management applications. Then, further details are provided on Trimble's development of the AVL system that uses a deep integration where the dead reckoning subsystem is continually calibrated by the GPS measurements when GPS is available; then the dead reckoning continues alone with newly calibrated drift parameters when the GPS signal is interrupted.

  14. Using Evolutionary Computation on GPS Position Correction

    PubMed Central

    2014-01-01

    More and more devices are equipped with global positioning system (GPS). However, those handheld devices with consumer-grade GPS receivers usually have low accuracy in positioning. A position correction algorithm is therefore useful in this case. In this paper, we proposed an evolutionary computation based technique to generate a correction function by two GPS receivers and a known reference location. Locating one GPS receiver on the known location and combining its longitude and latitude information and exact poisoning information, the proposed technique is capable of evolving a correction function by such. The proposed technique can be implemented and executed on handheld devices without hardware reconfiguration. Experiments are conducted to demonstrate performance of the proposed technique. Positioning error could be significantly reduced from the order of 10 m to the order of 1 m. PMID:24578657

  15. A review of GPS-based tracking techniques for TDRS orbit determination

    NASA Technical Reports Server (NTRS)

    Haines, B. J.; Lichten, S. M.; Malla, R. P.; Wu, S.-C.

    1993-01-01

    This article evaluates two fundamentally different approaches to the Tracking and Data Relay Satellite (TDRS) orbit determination utilizing Global Positioning System (GPS) technology and GPS-related techniques. In the first, a GPS flight receiver is deployed on the TDRS. The TDRS ephemerides are determined using direct ranging to the GPS spacecraft, and no ground network is required. In the second approach, the TDRS's broadcast a suitable beacon signal, permitting the simultaneous tracking of GPS and Tracking and Data Relay Satellite System satellites by ground receivers. Both strategies can be designed to meet future operational requirements for TDRS-II orbit determination.

  16. The Effect of Helicopter Rotors on GPS Signal Reception

    NASA Astrophysics Data System (ADS)

    Brodin, Gary; Cooper, John; Walsh, David; Stevens, Jeff

    2005-09-01

    This paper presents the results of an experiment to investigate the impact of helicopter rotor blades on GPS signal reception. An offshore transport helicopter was equipped with a measurement system including a TSO-C129 compliant receiver and a custom research receiver. GPS signals passing through rotor discs of this aircraft were found to suffer a reduction in received signal strength, leading to potential navigation and RAIM availability concerns. The phenomenon will vary between installations and receiver types. Test procedures to identify the occurrence of the phenomenon in operational GPS installations are presented, together with possible in-service monitoring programs to assess the impact on the navigation function.

  17. MicroBlaze implementation of GPS/INS integrated system on Virtex-6 FPGA.

    PubMed

    Bhogadi, Lokeswara Rao; Gottapu, Sasi Bhushana Rao; Konala, Vvs Reddy

    2015-01-01

    The emphasis of this paper is on MicroBlaze implementation of GPS/INS integrated system on Virtex-6 field programmable gate array (FPGA). Issues related to accuracy of position, resource usage of FPGA in terms of slices, DSP48, block random access memory, computation time, latency and power consumption are presented. An improved design of a loosely coupled GPS/INS integrated system is described in this paper. The inertial navigation solution and Kalman filter computations are provided by the MicroBlaze on Virtex-6 FPGA. The real time processed navigation solutions are updated with a rate of 100 Hz. PMID:26543763

  18. Key solutions to WEB-GIS based GPS vehicle monitoring system

    NASA Astrophysics Data System (ADS)

    Tan, Jian; Gao, Liang; Zhang, Jian Bing; Ren, Yingchao; Wu, Lei; Sheng, Lei

    2007-11-01

    Using Web-GIS to implement GPS monitoring is a promising implementation mode for public service and GPS monitoring in big organization. The critical bottle neck is the bandwidth, because both geographic maps and vehicle positioning data in the system are mass and they need to be transmitted frequently. In this paper, we illustrate five methods to solve this problem. The performances demonstrated in practicing application confirm the validity of these measures. Finally, the system achieves the balance between computational efficiency and transmission speed on internet and gains a nice user experience.

  19. Autonomous Navigation of the SSTI/Lewis Spacecraft Using the Global Positioning System (GPS)

    NASA Technical Reports Server (NTRS)

    Hart, R. C.; Long, A. C.; Lee, T.

    1997-01-01

    The National Aeronautics and Space Administration (NASA) Goddard Space Flight Center (GSFC) Flight Dynamics Division (FDD) is pursuing the application of Global Positioning System (GPS) technology to improve the accuracy and economy of spacecraft navigation. High-accuracy autonomous navigation algorithms are being flight qualified in conjunction with GSFC's GPS Attitude Determination Flyer (GADFLY) experiment on the Small Satellite Technology Initiative (SSTI) Lewis spacecraft, which is scheduled for launch in 1997. Preflight performance assessments indicate that these algorithms can provide a real-time total position accuracy of better than 10 meters (1 sigma) and velocity accuracy of better than 0.01 meter per second (1 sigma), with selective availability at typical levels. This accuracy is projected to improve to the 2-meter level if corrections to be provided by the GPS Wide Area Augmentation System (WAAS) are included.

  20. Office of Spaceflight Standard Spaceborne Global Positioning System (GPS) user equipment project

    NASA Technical Reports Server (NTRS)

    Saunders, Penny E.

    1991-01-01

    The Global Positioning System (GPS) provides the following: (1) position and velocity determination to support vehicle GN&C, precise orbit determination, and payload pointing; (2) time reference to support onboard timing systems and data time tagging; (3) relative position and velocity determination to support cooperative vehicle tracking; and (4) attitude determination to support vehicle attitude control and payload pointing.

  1. Augmented reality using GPS

    NASA Astrophysics Data System (ADS)

    Kim, Juwan; Kim, Haedong; Jang, Byungtae; Kim, Jungsik; Kim, Donghyun

    1998-04-01

    This paper describes a prototype system to be developing using GPS (Global Positioning System) as a tracker in order to combine real images with virtual geographical images in real time. To cover long distances, this system is built using a monitor-based configuration and divided into two parts. One is the real scene acquisition system that includes a vehicle, a wireless CCD camera, a GPS attitude determination device and a wireless data communication device. The other is the processing and visualization system that includes a wireless data communication device, a PC with a video overlay card and a 3D graphics accelerator. The pilot area of the current system is the part of SERI (Systems Engineering Research Institute) which is the institute we are working for now. And virtual objects are generated with 3D modeling data of the main building, the new building to be planned, and so on in SERI. The wireless CCD camera attached to a vehicle acquires the real scenes. And GPS attitude determination device produces a wireless CCD camera's position and orientation data. And then this information is transmitted to the processing and visualization part by air. In the processing and visualization system, virtual images are rendered using the received information and combined with the real scenes. Applications are an enhanced bird's-eye view and disaster rescue work such as earthquake.

  2. GPS as an orbit determination subsystems

    NASA Technical Reports Server (NTRS)

    Fennessey, Richard; Roberts, Pat; Knight, Robin; Vanvolkinburg, Bart

    1995-01-01

    This paper evaluates the use of Global Positioning System (GPS) receivers as a primary source of tracking data for low-Earth orbit satellites. GPS data is an alternative to using range, azimuth, elevation, and range-rate (RAER) data from the Air Force Satellite Control Network antennas, the Space Ground Link System (SGLS). This evaluation is applicable to missions such as Skipper, a joint U.S. and Russian atmosphere research mission, that will rely on a GPS receiver as a primary tracking data source. The Detachment 2, Space and Missile Systems Center's Test Support Complex (TSC) conducted the evaluation based on receiver data from the Space Test Experiment Platform Mission O (STEP-O) and Advanced Photovoltaic and Electronics Experiments (APEX) satellites. The TSC performed orbit reconstruction and prediction on the STEP-0 and APEX vehicles using GPS receiver navigation solution data, SGLS RAER data, and SGLS anglesonly (azimuth and elevation) data. For the STEP-O case, the navigation solution based orbits proved to be more accurate than SGLS RAER based orbits. For the APEX case, navigation solution based orbits proved to be less accurate than SGLS RAER based orbits for orbit prediction, and results for orbit reconstruction were inconclusive due to the lack of a precise truth orbit. After evaluating several different GPS data processing methods, the TSC concluded that using GPS navigation solution data is a viable alternative to using SGLS RAER data.

  3. Geodetic point positioning with GPS (Global Positioning System) carrier beat phase data from the CASA (Central and South America) Uno experiment

    SciTech Connect

    Malys, S.; Jensen, P.A. )

    1990-04-01

    The Global Positioning System (GPS) carrier beat phase data collected by the TI4100 GPS receiver has been successfully utilized by the US Defense Mapping Agency in an algorithm which is designed to estimate individual absolute geodetic point positions from data collected over a few hours. The algorithm uses differenced data from one station and two to four GPS satellites at a series of epochs separated by 30 second intervals. The precise GPS ephemerides and satellite clock states, held fixed in the estimation process, are those estimated by the Naval Surface Warfare Center (NSWC). Broadcast ephemerides and clock states are also utilized for comparative purposes. An outline of the data corrections applied, the mathematical model and the estimation algorithm are presented. Point positioning results and statistics are presented for a globally-distributed set of stations which contributed to the CASA Uno experiment. Statistical assessment of 114 GPS point positions at 11 CASA Uno stations indicates that the overall standard deviation of a point position component, estimated from a few hours of data, is 73 centimeters. Solution of the long line geodetic inverse problem using repeated point positions such as these can potentially offer a new tool for those studying geodynamics on a global scale.

  4. GPS Position and Heading Circuitry for Ships

    NASA Technical Reports Server (NTRS)

    Cooke, Michael P.; Yim, Hester J.; Gomez, Susan F.

    2003-01-01

    Circuit boards that contain radio-frequency (RF) and digital circuitry have been developed by NASA to satisfy a requirement of the Port of Houston Authority for relatively inexpensive Global Positioning System (GPS) receivers that indicate the azimuthal headings as well as the positions of ships. The receiver design utilizes the unique architecture of the Mitel commercial chip-set, which provides for an accurate GPS-based heading-determination device. The major components include two RF front ends (each connected to a separate antenna), a surface-acoustic-wave intermediate-frequency filter between second- and third-stage mixers, a correlator, and a reduced-instruction- set computer. One of the RF front ends operates as a master, the other as a slave. Both RF front ends share a 10-MHz sinusoidal clock oscillator, which provides for more accurate carrier phase measurements between the two antennas. The outputs of the RF front ends are subjected to conventional GPS processing. The commercial-based chip-set design approach provides an inexpensive open architecture GPS platform, which can be used in developing and implementing unique GPS-heading and attitude-determination algorithms for specific applications. The heading is estimated from the GPS position solutions of the two antennas by an algorithm developed specifically for this application. If a third (and preferably a fourth) antenna were added, it would be possible to estimate the attitude of the GPS receiver in three dimensions instead of only its heading in a horizontal plane.

  5. Global Positioning System (GPS) advances in autonomous user system (Norway demonstration)

    NASA Astrophysics Data System (ADS)

    Ananda, Mohan P.; Bernstein, Harold; Feess, William A.; Kells, Ronald C.; Wortham, J. H.

    Using a new autonomous user (AU) system algorithm extends the AU system concept by permitting the use of a crystal frequency reference instead of an atomic reference. Results obtained using both crystal and atomic frequency references are presented. To supply interim full-system accuracy in the event of loss of the operational control segment (OCS) of GPS, an AU system needing only user segment modification has been implemented. During the summer of 1988 a demonstration of the system was conducted in Tromso, Norway. It is indicated, that in this 180-day test period, the autonomous user with a crystal reference could achieve a navigation accuracy of the same order of magnitude as when the OCS was operating. Furthermore, other navigation systems may utilize the concepts of this autonomous user system.

  6. Study of Lever-Arm Effect Using Embedded Photogrammetry and On-Board GPS Receiver on Uav for Metrological Mapping Purpose and Proposal of a Free Ground Measurements Calibration Procedure

    NASA Astrophysics Data System (ADS)

    Daakir, M.; Pierrot-Deseilligny, M.; Bosser, P.; Pichard, F.; Thom, C.; Rabot, Y.

    2016-03-01

    Nowadays, Unmanned Aerial Vehicle (UAV) on-board photogrammetry knows a significant growth due to the democratization of using drones in the civilian sector. Also, due to changes in regulations laws governing the rules of inclusion of a UAV in the airspace which become suitable for the development of professional activities. Fields of application of photogrammetry are diverse, for instance: architecture, geology, archaeology, mapping, industrial metrology, etc. Our research concerns the latter area. Vinci-Construction- Terrassement is a private company specialized in public earthworks that uses UAVs for metrology applications. This article deals with maximum accuracy one can achieve with a coupled camera and GPS receiver system for direct-georeferencing of Digital Surface Models (DSMs) without relying on Ground Control Points (GCPs) measurements. This article focuses specially on the lever-arm calibration part. This proposed calibration method is based on two steps: a first step involves the proper calibration for each sensor, i.e. to determine the position of the optical center of the camera and the GPS antenna phase center in a local coordinate system relative to the sensor. A second step concerns a 3d modeling of the UAV with embedded sensors through a photogrammetric acquisition. Processing this acquisition allows to determine the value of the lever-arm offset without using GCPs.

  7. Waste receiving and processing plant control system; system design description

    SciTech Connect

    LANE, M.P.

    1999-02-24

    The Plant Control System (PCS) is a heterogeneous computer system composed of numerous sub-systems. The PCS represents every major computer system that is used to support operation of the Waste Receiving and Processing (WRAP) facility. This document, the System Design Description (PCS SDD), includes several chapters and appendices. Each chapter is devoted to a separate PCS sub-system. Typically, each chapter includes an overview description of the system, a list of associated documents related to operation of that system, and a detailed description of relevant system features. Each appendice provides configuration information for selected PCS sub-systems. The appendices are designed as separate sections to assist in maintaining this document due to frequent changes in system configurations. This document is intended to serve as the primary reference for configuration of PCS computer systems. The use of this document is further described in the WRAP System Configuration Management Plan, WMH-350, Section 4.1.

  8. MicroGPS for Low-Cost Orbit Determination

    NASA Astrophysics Data System (ADS)

    Wu, S. C.; Bertiger, W. I.; Kuang, D.; Lichten, S. M.; Nandi, S.; Romans, L. J.; Srinivasan, J. M.

    1997-07-01

    This article presents a new technology for satellite orbit determination using a simple Global Positioning System (GPS) receiver (microGPS) with ultra-low cost, power, and mass. The capability of low-cost orbit determination with microGPS for a low Earth-orbiting satellite, Student Nitric Oxide Explorer (SNOE), is demonstrated using actual GPS data from the GPS/Meteorology (MET) satellite. The measurements acquired by the microGPS receiver will be snapshots of carrier Doppler and ambiguous pseudorange. Among the challenges in orbit determination are the resolution of the pseudorange ambiguity; the estimation of the measurement time tag drift, which effects the in-track orbit position solution; and the convergence of the orbit solution from a cold start with essentially no knowledge of the orbit. The effects of data gaps and Doppler data quality are investigated. An efficient data acquisition scenario for SNOE is derived.

  9. The Continuous Generation of Equatorial Plasma Bubbles during the Passage of the Solar Terminator, Observed with a Densely-Clustered Network of GPS Receivers in Southeast Asia.

    NASA Astrophysics Data System (ADS)

    Buhari, S. M.; Tsunoda, R. T.; Abdullah, M.; Hasbi, A. M.; Otsuka, Y.; Yokoyama, T.; Nishioka, M.; Tsugawa, T.

    2014-12-01

    Equatorial plasma bubbles (EPBs) are three-dimensional structures of depleted plasma density that are often observed in the nighttime equatorial ionosphere. They are initiated near the magnetic dip equator, in the bottomside of the F layer, and develop with time, upward in altitude and poleward in latitude (into both hemispheres), taking the form of longitudinally-narrow, vertically-extended wedges that penetrate deep into the topside of the F layer. Moreover, these structures drift zonally as they evolve in time. Much of what is not yet known about EPBs stems from our inability (1) to capture spatial descriptions of these structures, and (2) to monitor their evolution as a function of time. An objective of this presentation is to report the existence and availability of total electron content (TEC) data from densely-clustered networks of GPS receivers that are capable of providing time-continuous descriptions of EPBs with both high spatial resolution and broad geographical coverage. The networks include the Malaysia Real-Time Kinematics GNSS Network (MyRTKnet), Sumatera GPS Array (SUGAR) network and International GNSS Service (IGS) located in Southeast Asia (SEA). These networks contain 127 GPS receivers with average spacing of about 50 to 100 km. With the ability to resolve space-time ambiguities, we are able to follow the temporal evolution of EPB structures over an extended longitude sector (90 to 120 degrees, East longitude). We will present results from a case study (April 5, 2011) in which 16 EPBs were detected in longitude and tracked in time. We show, for the first time, that the births of 10 out of 16 observed EPBs coincided with the time of passage of the solar terminator across the longitude of birth. The distance between birth locations varied between 100 and 550 km with 10-minute interval. These EPBs were found to persist for 50 minutes to 7 hours, while drifting eastward at a speed of 92 to 150 ms-1. The finding that as many as 16 EPBs can be

  10. Jammers in the commercial world of GPS

    SciTech Connect

    Wollschlager, B.

    1994-12-31

    The military world of electronic countermeasures is an enviromnent where receivers are designed to perform in a high level of interference or jamming. The electronic battlefield is full of radio frequency interference, both intentional and unintentional, which disrupts communications, fools radar, overloads guidance systems, and in general causes havoc with sensitive electronic systems such as GPS receivers. The commercial radio world is also becoming more electronically hazardous. The FCC has adopted certain emission standards which attempt to control how much ``noise`` electronic devices give off; however, these standards are much less stringent than their military counterparts. For GPS signals with typical power levels of {minus}125 dBm the interfering signals can pose a large in-band or near-band problem. Because the spread spectrum signal exists below thermal noise, any in-band noise also poses a large challenge to GPS reception. Harmonics from a cellular phone, a UHF radio, or a personal computer can cause a GPS receiver to be unable to navigate. Recognition of this problem is causing filter performance profiles such as ARINC 743A and others to become popular for GPS receiver interference rejection. This paper is based on Rockwell`s experience on Navstar GPS programs such as PLGR.

  11. Real-time ultrasound-guided PCNL using a novel SonixGPS needle tracking system.

    PubMed

    Li, Xiang; Long, Qingzhi; Chen, Xingfa; He, Dalin; Dalin, He; He, Hui

    2014-08-01

    SonixGPS is a successful ultrasound guidance position system. It helps to improve accuracy in performing complex puncture operations. This study firstly used SonixGPS to perform kidney calyx access in PCNL to investigate its effectiveness and safety. This was a prospectively randomized controlled study performed from September 2011 to October 2012. A total of 97 patients were prospectively randomized into two groups using random number generated from SAS software. 47 Patients were enrolled in conventional ultrasound-guided (US-guided) group and 50 patients were classified into SonixGPS-guided group. Nine patients were lost during follow-up. Hence, a total of 88 patients were qualified and analyzed. Preoperative examinations included urine analysis, urine culture, kidney function, coagulation profile and routine analysis of blood. Ultrasonography was used to evaluate the degree of hydronephrosis. The intraoperative findings, including blood loss, operating time, time to successful puncture, the number of attempts for successful puncture and hospital stay were recorded. The stone clearance rate and complications were analyzed. The present study showed no significant difference between the two groups in terms of demographic data, preoperative markers, stone clearance rate and the stone composition. However, the time to successful puncture, the number of trials for successful puncture, operating time and hospital length of stay were significantly decreased in the SonixGPS-guided group. Furthermore, the hemoglobin decrease was also obviously lower in the SonixGPS group than that in conventional US-guided group. SonixGPS needle tacking system guided PCNL is safe and effective in treating upper urinary tract stones. This novel technology makes puncturing more accuracy and can significantly decrease the incidence of relative hemorrhage and accelerate recovery. PMID:24965272

  12. A MMC/MIMU/GPS integrated attitude and azimuth determination system

    NASA Astrophysics Data System (ADS)

    Sheng, Wei; Ma, Yanwu; Cao, Juanjuan

    2008-10-01

    Exact knowledge of attitude and azimuth is a fundamental factor in steering vehicle and robot (called carrier in this paper). Micro inertial measurement unit (MIMU), i.e. IMU made by silicon MEMS inertial sensors, GPS and MEMS magnetic compass (MMC), are often used in traditional low-cost attitude and azimuth determination solutions. The main discrepancy, in all of these low-cost approaches, is that the azimuth output is affected by acceleration and turns for long-playing carriers. This paper puts forward a MMC/MIMU/GPS integrated system and an iterative attitude & azimuth determination algorithm for long-playing accelerated carrier's motion. GPS output (.i.e. position and velocity), in ENU (East-North-Upward) navigation frame is transformed into body frame by transformation matrix Cbn. By integrating the MIMU and GPS measurements, through Kalman Filter (KF), the three orthogonal components of the gravity vector are precisely estimated in body frame despite the acceleration effects. Pitch and roll angles are calculated by gravity vector components in body frame, where as azimuth angle is calculated by combining pitch angle, roll angle and MMC output. The direction cosine matrix Cbn, updated by the latest azimuth, roll and pitch angles, is used in next round of this iterative attitude & azimuth determination algorithm. CFAR (Constant False Alarm Rate) filters have been utilized to suppress the noise in GPS data caused by differential operation. The proposed iterative algorithm has been practically implemented and simulated. The simulations results prove the ability of the MMC/MIMU/GPS integrated system to determine the attitude and azimuth for long-playing carrier in any motion situation.

  13. Operational Use of GPS Navigation for Space Shuttle Entry

    NASA Technical Reports Server (NTRS)

    Goodman, John L.; Propst, Carolyn A.

    2008-01-01

    The STS-118 flight of the Space Shuttle Endeavour was the first shuttle mission flown with three Global Positioning System (GPS) receivers in place of the three legacy Tactical Air Navigation (TACAN) units. This marked the conclusion of a 15 year effort involving procurement, missionization, integration, and flight testing of a GPS receiver and a parallel effort to formulate and implement shuttle computer software changes to support GPS. The use of GPS data from a single receiver in parallel with TACAN during entry was successfully demonstrated by the orbiters Discovery and Atlantis during four shuttle missions in 2006 and 2007. This provided the confidence needed before flying the first all GPS, no TACAN flight with Endeavour. A significant number of lessons were learned concerning the integration of a software intensive navigation unit into a legacy avionics system. These lessons have been taken into consideration during vehicle design by other flight programs, including the vehicle that will replace the Space Shuttle, Orion.

  14. Tractor-mounted, GPS-based spot fumigation system manages Prunus replant disease

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Our research goal was to use recent advances in global positioning system (GPS) and computer technology to apply just the right amount of fumigant where it is most needed (i.e., in a small target treatment zone in and around each tree replanting site) to control Prunus replant disease (PRD). We deve...

  15. Road safety alerting system with radar and GPS cooperation in a VANET environment

    NASA Astrophysics Data System (ADS)

    Santamaria, Amilcare Francesco; Sottile, Cesare; De Rango, Floriano; Voznak, Miroslav

    2014-05-01

    New applications in wireless environments are increasing and keeping even more interests from the developer companies and researchers. In particular, in these last few years the government and institutional organization for road safety spent a lot of resources and money to promote Vehicular Ad-Hoc Network (VANET) technology, also car manufactures are giving a lot of contributions on this field as well. In our paper, we propose an innovative system to increase road safety, matching the requests of the market allowing a cooperation between on-board devices. The vehicles are equipped with On Board Unit (OBU) and On Board Radar Unit (OBRU), which can spread alerting messages around the network regarding warning and dangerous situations exploiting IEEE802.llp standard. Vehicles move along roads observing the environment, traffic and road conditions, and vehicles parameters as well. These information can be elaborated and shared between neighbors, Road Side Unit (RSU)s and, of course, with Internet, allowing inter-system communications exploiting an Road Traffic Manager (RTM). Radar systems task it the detection of the environment in order to increase the knowledge of current conditions of the roads, for example it is important to identify obstacles, road accidents, dangerous situations and so on. Once detected exploiting onboard devices, such as Global Position System (GPS) receiver it is possible to know the exact location of the caught event and after a data elaboration the information is spread along the network. Once the drivers are advised, they can make some precautionary actions such as reduction of traveling speed or modification of current road path. In this work the routing algorithms, which have the main goal to rapidly disseminate information, are also been investigated.

  16. 7 CFR 400.209 - Electronic transmission and receiving system.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... Contract-Standards for Approval § 400.209 Electronic transmission and receiving system. Any Contractor under the Contract is required to: (a) Adopt a plan for the purpose of transmitting and receiving... 7 Agriculture 6 2010-01-01 2010-01-01 false Electronic transmission and receiving system....

  17. Demonstration of the fiducial concept using data from the March 1985 GPS field test

    NASA Technical Reports Server (NTRS)

    Davidson, J. M.; Thornton, C. L.; Stephens, S. A.; Wu, S. C.; Lichten, S. M.; Border, J. S.; Sovers, O. J.; Dixon, T. H.; Williams, B. G.

    1986-01-01

    The first field test of NASA's Global Positioning System (GPS) Geodetic Program took place in March of 1985. The principal objective of this test was the demonstration of the feasibility of the fiducial station approach to precise GPS-based geodesy and orbit determination. Other objectives included an assessment of the performance of the several GPS receiver types involved in these field tests and the testing of the GIPSY software for GPS data analysis. In this article, the GIPSY (GPS Inferred Positioning System) software system is described and baseline solutions are examined for consistency with independent measurements made using very long baseline interferometry.

  18. The Development of M3S-Based GPS Navchair and Tele-Monitor System.

    PubMed

    Wu, Yi-Hui; Lu, Bing-Yuh; Chen, Heng-Yin; Ou-Yang, Yao; Lai, Jin-Shin; Kuo, Te-Son; Chong, Fok-Ching

    2005-01-01

    The purpose of this study is to develop a M3S- Based GPS navigation system for power wheelchair. The wheelchair steered with GPS and electronic compass can move automatically toward a specific destination through a GIS-Map in the computer. The topic of this study is to help people with disabilities regain independence of transportation in specific areas of their daily activities. This system is now designed to operate in special locations, for example, campuses or airports. Safety of the system is enhanced according to "M3S", which is an international standard for power wheelchair. In the proposed architecture, modules are easily and securely integrated to the wheelchair, which includes a tele-monitor system implemented with computer network, mobile-phone and physiological sensors. Bio-signals, wheelchair location and other information of the user are acquired by the nursing staff or any other medical personnel by using this system. PMID:17281122

  19. Improved positioning by addition of atmospheric corrections to local area differential GPS

    NASA Astrophysics Data System (ADS)

    Singh, Malkiat; Reilly, Michael H.

    2006-10-01

    A local area differential GPS (DGPS) method applies corrections from a reference GPS receiver to improve positioning accuracy for a roaming GPS receiver. Increasing separation between reference and roaming receivers dilutes this improvement, largely because ionospheric and tropospheric effects differ between their two locations. We correct differential corrections for this difference and determine the improvement with this "atmospheric" DGPS method at roaming receiver positions that are separated from a Coast Guard reference receiver at Annapolis, Maryland, by 44, 67, and 228 km. For ionospheric corrections we use our Raytrace-Ionospheric conductivity and electron density-Bent-Gallagher ionospheric propagation model with driving parameters obtained from two-frequency data of surveyed reference GPS receivers. For tropospheric corrections we use the Hopfield model and weather station data for surface temperature, pressure, and relative humidity. Internet delivery of atmospheric differential corrections is used to avoid blockage or range cutoff of radio transmissions. Some comparisons are made with Wide Area Augmentation System GPS receiver performance.

  20. Towards GPS Surface Reflection Remote Sensing of Sea Ice Conditions

    NASA Technical Reports Server (NTRS)

    Komjathy, A.; Maslanik, J. A.; Zavorotny, V. U.; Axelrad, P.; Katzberg, S. J.

    2000-01-01

    This paper describes the research to extend the application of Global Positioning System (GPS) signal reflections, received by airborne instruments, to cryospheric remote sensing. The characteristics of the GPS signals and equipment afford the possibility of new measurements not possible with existing radar and passive microwave systems. In particular, the GPS receiving systems are small and light-weight, and as such are particularly well suited to be deployed on small aircraft or satellite platforms with minimal impact. Our preliminary models and experimental results indicate that reflected GPS signals have potential to provide information on the presence and condition of sea and fresh-water ice as well as the freeze/thaw state of frozen ground. In this paper we show results from aircraft experiments over the ice pack near Barrow, Alaska suggesting correlation between forward scattered GPS returns and RADARSAT backscattered signals.

  1. Transition of NOAA's GPS-Met Data Acquisition and Processing System to the Commercial Sector

    NASA Astrophysics Data System (ADS)

    Jackson, M. E.; Holub, K.; Callahan, W.; Blatt, S.

    2014-12-01

    In April of 2014, NOAA/OAR/ESRL Global Systems Division (GSD) and Trimble, in collaboration with Earth Networks, Inc. (ENI) signed a Cooperative Research and Development Agreement (CRADA) to transfer the existing NOAA GPS-Met Data Acquisition and Processing System (GPS-Met DAPS) technology to a commercial Trimble/ENI partnership. NOAA's GPS-Met DAPS is currently operated in a pseudo-operational mode but has proven highly reliable and running at over 95% uptime. The DAPS uses the GAMIT software to ingest dual frequency carrier phase GPS/GNSS observations and ancillary information such as real-time satellite orbits to estimate the zenith-scaled tropospheric (ZTD) signal delays and, where surface MET data are available, retrieve integrated precipitable water vapor (PWV). The NOAA data and products are made available to end users in near real-time. The Trimble/ENI partnership will use the Trimble Pivot™ software with the Atmosphere App to calculate zenith tropospheric (ZTD), tropospheric slant delay, and integrated precipitable water vapor (PWV). Evaluation of the Trimble software is underway starting with a comparison of ZTD and PWV values determined from GPS stations located near NOAA Radiosonde Observation (Upper-Air Observation) launch sites. A success metric was established that requires Trimble's PWV estimates to match ESRL/GSD's to within 1.5 mm 95% of the time, which corresponds to a ZTD uncertainty of less than 10 mm 95% of the time. Initial results indicate that Trimble/ENI data meet and exceed the ZTD metric, but for some stations PWV estimates are out of specification. These discrepancies are primarily due to how offsets between MET and GPS stations are handled and are easily resolved. Additional test networks are proposed that include low terrain/high moisture variability stations, high terrain/low moisture variability stations, as well as high terrain/high moisture variability stations. We will present results from further testing along with a timeline

  2. GPS Moving Vehicle Experiment

    NASA Technical Reports Server (NTRS)

    Oaks, O. J.; Reid, Wilson; Wright, James; Duffey, Christopher; Williams, Charles; Warren, Hugh; Zeh, Tom; Buisson, James

    1996-01-01

    The Naval Research Laboratory (NRL) in the development of timing systems for remote locations, had a technical requirement for a Y code (SA/AS) Global Positioning System (GPS) precise time transfer receiver (TTR) which could be used both in a stationary mode or mobile mode. A contract was awarded to the Stanford Telecommunication Corporation (STEL) to build such a device. The Eastern Range (ER) als had a requirement for such a receiver and entered into the contract with NRL for the procurement of additional receivers. The Moving Vehicle Experiment (MVE) described in this paper is the first in situ test of the STEL Model 5401C Time Transfer System in both stationary and mobile operations. The primary objective of the MVE was to test the timing accuracy of the newly developed GPS TTR aboard a moving vessel. To accomplish this objective, a joint experiment was performed with personnel from NRL and the er at the Atlantic Undersea Test and Evaluation Center (AUTEC) test range at Andros Island. Results and discussion of the test are presented in this paper.

  3. Precision GPS ephemerides and baselines

    NASA Technical Reports Server (NTRS)

    1992-01-01

    The required knowledge of the Global Positioning System (GPS) satellite position accuracy can vary depending on a particular application. Application to relative positioning of receiver locations on the ground to infer Earth's tectonic plate motion requires the most accurate knowledge of the GPS satellite orbits. Research directed towards improving and evaluating the accuracy of GPS satellite orbits was conducted at the University of Texas Center for Space Research (CSR). Understanding and modeling the forces acting on the satellites was a major focus of the research. Other aspects of orbit determination, such as the reference frame, time system, measurement modeling, and parameterization, were also investigated. Gravitational forces were modeled by truncated versions of extant gravity fields such as, Goddard Earth Model (GEM-L2), GEM-T1, TEG-2, and third body perturbations due to the Sun and Moon. Nongravitational forces considered were the solar radiation pressure, and perturbations due to thermal venting and thermal imbalance. At the GPS satellite orbit accuracy level required for crustal dynamic applications, models for the nongravitational perturbation play a critical role, since the gravitational forces are well understood and are modeled adequately for GPS satellite orbits.

  4. GPS, GNSS, and Ionospheric Density Gradients

    NASA Astrophysics Data System (ADS)

    Kintner, P. M.; O'Hanlon, B.; Humphreys, T. E.

    2009-12-01

    Ionospheric density and density gradients affect GNSS signals in two ways. They can introduce ranging errors or irregularities that form on the density gradients producing scintillation. Here we focus on the issue of ranging errors. There are two approaches to mitigating ranging errors produced by ionospheric density gradients which can be 20-30 m during major magnetic storms. The first approach is to use a reference receiver(s) to determine the ionospheric contribution to ranging errors. The ranging error is then transmitted to the user for correction within the mobile receiver. This approach is frequently referred to as differential GPS and, when multiple reference receivers are used, the system is referred to as an augmentation system. This approach is vulnerable to ionospheric gradients depending on the reference receiver spacing(s) and latency in applying the correction within the mobile receiver. The second approach is to transmit navigation signals at two frequencies and then use the relative delay between the two signals to both estimate the ranging error and calculate the correct range. Currently the dual frequency technique is used by US military receivers with an encryption key and some civilian receivers which must be stationary and average over times long compared to those required for navigation. However, the technology of space based radio navigation is changing. GPS will soon be a system with three frequencies and multiple codes. Furthermore Europe, Russia, and China are developing independent systems to complement and compete with GPS while India and Japan are developing local systems to enhance GPS performance in their regions. In this talk we address two questions. How do density gradients affect augmentation systems including the social consequences and will the new GPS/GNSS systems with multiple civilian frequencies be able to remove ionospheric errors. The answers are not at all clear.

  5. IRI-vTEC versus GPS-vTEC for Nigerian SCINDA GPS stations

    NASA Astrophysics Data System (ADS)

    Okoh, Daniel; McKinnell, Lee-Anne; Cilliers, Pierre; Okere, Bonaventure; Okonkwo, Chinelo; Rabiu, Babatunde

    2015-04-01

    Following the recent proliferation of dual-frequency GPS (Global Positioning System) receiver systems across the African continent, there is a growing number of papers that compare vertical Total Electron Content (vTEC) values derived from the International Reference Ionosphere (IRI) model with those obtained from the GPS receiver measurements. In this work we report an investigation of IRI-vTEC versus GPS-vTEC comparisons for three Nigerian SCINDAGPS stations (Nsukka, Ilorin, and Lagos) for which data are available in the year 2012, and present a further review of the differences/similarities observed between them. Since a major interest in this work is to use the GPS measurements to improve the predictions of the IRI model for the region, we present a detailed regression analysis of differences between the two sources in a manner that will benefit this application.

  6. 7 CFR 400.209 - Electronic transmission and receiving system.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 6 2011-01-01 2011-01-01 false Electronic transmission and receiving system. 400.209... Contract-Standards for Approval § 400.209 Electronic transmission and receiving system. Any Contractor...; (b) Maintain an electronic system which must be tested and approved by the Corporation; (c)...

  7. 7 CFR 400.209 - Electronic transmission and receiving system.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 6 2012-01-01 2012-01-01 false Electronic transmission and receiving system. 400.209... Contract-Standards for Approval § 400.209 Electronic transmission and receiving system. Any Contractor... Corporation approval of the electronic system as a condition to the electronic transmission and reception...

  8. 7 CFR 400.209 - Electronic transmission and receiving system.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 6 2013-01-01 2013-01-01 false Electronic transmission and receiving system. 400.209... Contract-Standards for Approval § 400.209 Electronic transmission and receiving system. Any Contractor... Corporation approval of the electronic system as a condition to the electronic transmission and reception...

  9. 7 CFR 400.209 - Electronic transmission and receiving system.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 6 2014-01-01 2014-01-01 false Electronic transmission and receiving system. 400.209... Contract-Standards for Approval § 400.209 Electronic transmission and receiving system. Any Contractor... Corporation approval of the electronic system as a condition to the electronic transmission and reception...

  10. An Investigation of Multipath Effects on the GPS System During Auto-Rendezvous and Capture

    NASA Technical Reports Server (NTRS)

    Richie, James E.; Forest, Francis W.

    1995-01-01

    The proposed use of a Cargo Transport Vehicle (CTV) to carry hardware to the Space Station Freedom (SSF) during the construction phase of the SSF project requires remote maneuvering of the CTV. The CTV is not a manned vehicle. Obtaining the relative positions of the CTV and SSF for remote auto-rendezvous and capture (AR&C) scenarios will rely heavily on the Global Positioning System (GPS). The GPS system is expected to guide the CTV up to a distance of 100 to 300 meters from the SSF. At some point within this range, an optical docking system will take over the remote guidance for capture. During any remote guidance by GPS it is possible that significant multipath signals may be caused by large objects in the vicinity of the module being remotely guided. This could alter the position obtained by the GPS system from the actual position. Due to the nature of the GPS signals, it has been estimated that if the difference in distance between the Line of Sight (LOS) path and the multipath is greater than 300 meters, the GPS system is capable of discriminating between the direct signal and the reflected (or multipath) signal. However, if the path difference is less than 300 meters, one must be concerned. This report details the work accomplished by the Electromagnetic Simulations Laboratory at Marquette University over the period December 1993 to May 1995. This work is an investigation of the strength and phase of a multipath signal arriving at the CTV relative to the direct or line of sight (LOS) signal. The signal originates at a GPS satellite in half geo-stationary orbit and takes two paths to the CTV: (1) the direct or LOS path from the GPS satellite to the CTV; and (2) a scattered path from the GPS satellite to the SSF module and then to the CTV. The scattering from a cylinder has been computed using the physical optics approximation for the current. No other approximations or assumptions have been made including no assumptions regarding the far field or Fresnel field

  11. Autonomous reconfigurable GPS/INS navigation and pointing system for rendezvous and docking

    NASA Technical Reports Server (NTRS)

    Upadhyay, Triveni M.

    1991-01-01

    The briefing describes work using the Global Positioning System to determine position of spacecraft and the development of computer tools to utilize these position determinations to enable autonomous rendezvous. Using GPS data in conjunction with Inertial Navigation Systems (INS) provides the capability for absolute spacecraft navigation, navigation of one spacecraft relative to another, and attitude determination. Some results presented are based on limited observations, though simulation results are documented. A GPS/INS navigation flight experiment could provide a platform for evaluating approaches for autonomous operation and reconfigurability of the navigation and attitude determination subsystem for future space vehicles. Current emphasis is on the development and demonstration of an Onboard Mission Manager (OMM) and a Multi-Mode Navigation Kalman filter. Sensor data will be handed over to the OMM, which will determine the appropriate response and generate commands for the Kalman filter to use to reconfigure itself. Global Positioning System measurements and INS data will be processed in the integrated navigation filter and used to compute errors in position, velocity, and attitude. Inertial Navigation Systems instrument errors (biases, scale factors, etc.) also can be estimated. The OMM then will use a knowledge base to determine appropriate system response. The GPS is good for missions that have attitude pointing accuracy requirements within the 100 to 200 arcsecond range.

  12. A Self-Tuning Kalman Filter for Autonomous Navigation Using the Global Positioning System (GPS)

    NASA Technical Reports Server (NTRS)

    Truong, Son H.

    1999-01-01

    Most navigation systems currently operated by NASA are ground-based, and require extensive support to produce accurate results. Recently developed systems that use Kalman filter and GPS (Global Positioning Systems) data for orbit determination greatly reduce dependency on ground support, and have potential to provide significant economies for NASA spacecraft navigation. These systems, however, still rely on manual tuning from analysts. A sophisticated neuro-fuzzy component fully integrated with the flight navigation system can perform the self-tuning capability for the Kalman filter and help the navigation system recover from estimation errors in real time.

  13. Precise GPS orbit determination results from 1985 field tests

    NASA Technical Reports Server (NTRS)

    Lichten, S. M.; Border, J. S.; Wu, S.-C.; Williams, B. G.; Yunck, T. P.

    1986-01-01

    Data from three different receiver types have been used to obtain precise orbits for the satellites of the Global Positioning System (GPS). The data were collected during the 1985 March-April GPS experiment to test and validate GPS techniques for precision orbit determination and geodesy. A new software package developed at the Jet Propulsion Laboratory (JPL), GIPSY (GPS Inferred Positioning SYstem), was used to process the data. To assess orbit accuracy, solutions are compared using integrated doppler data from various different receiver types, different fiducial sites, and independent data arcs, including one spanning six days. From these intercomparisons, orbit accuracy for a well-tracked GPS satellite of three meters in altitude and about five meters in each of down and cross-track components are inferred.

  14. Autonomous Navigation Improvements for High-Earth Orbiters Using GPS

    NASA Technical Reports Server (NTRS)

    Long, Anne; Kelbel, David; Lee, Taesul; Garrison, James; Carpenter, J. Russell; Bauer, F. (Technical Monitor)

    2000-01-01

    The Goddard Space Flight Center is currently developing autonomous navigation systems for satellites in high-Earth orbits where acquisition of the GPS signals is severely limited This paper discusses autonomous navigation improvements for high-Earth orbiters and assesses projected navigation performance for these satellites using Global Positioning System (GPS) Standard Positioning Service (SPS) measurements. Navigation performance is evaluated as a function of signal acquisition threshold, measurement errors, and dynamic modeling errors using realistic GPS signal strength and user antenna models. These analyses indicate that an autonomous navigation position accuracy of better than 30 meters root-mean-square (RMS) can be achieved for high-Earth orbiting satellites using a GPS receiver with a very stable oscillator. This accuracy improves to better than 15 meters RMS if the GPS receiver's signal acquisition threshold can be reduced by 5 dB-Hertz to track weaker signals.

  15. Development of a new Tsunami Monitoring System Using a GPS Buoy

    NASA Astrophysics Data System (ADS)

    Kato, T.; Terada, Y.; Nagai, T.; Shimizu, K.; Tomita, T.; Koshimura, S.

    2008-12-01

    A tsunami monitoring system using a GPS buoy has been developed for more than ten years. Real-time kinematic (RTK) GPS technology was used for this purpose. After a series of preliminary experimental studies, the third experiment was conducted offshore Ofunato city, northern Tohoku, Japan. GPS antenna was set at the top of the buoy and the 1-sec sampling data were transmitted to the ground base of about 1.6km distance together with other ancillary data. The data was processed at the ground base and the estimated 3D positions were disseminated through internet. This system operated for about three years of 2001-2003 and succeeded to detect two tsunamis of about 10cm amplitude; 2001 Peru earthquake and 2003 Tokachi earthquake, by applying a simple filtering technique. After this successful experiment, the fourth system was newly designed and was established about 12km south of Muroto Promontory, southwestern Japan in early April 2004. The buoy has experienced nearby passages of several typhoons with a maximum wave of about 20meter and has shown a total integrity for an operational use. On September 5th 2004, a large earthquake of Mw7.4 occurred about 200km east of the buoy. The GPS buoy successfully recorded the tsunami with about 10cm amplitude at the first peak arrival of about 10 minutes before its arrival at the nearest coast of Muroto Promontory. The simulated record has shown excellent consistency with the observed tsunami, suggesting high potential for predicting tsunami height at the coast before its arrival, if the record is efficiently implemented in the tsunami warning system. The system has been adopted as a national sea-surface monitoring project and has been deployed at several locations around the Japanese coasts for monitoring also wind-waves.

  16. Determination of locational error associated with global positioning system (GPS) radio collars in relation to vegetation and topography in north-central New Mexico

    SciTech Connect

    Bennett, K.; Biggs, J.; Fresquez, P.R.

    1997-02-01

    In 1996, a study was initiated to assess seasonal habitat use and movement patterns of Rocky Mountain elk (Cervus elaphus nelsoni) using global positioning system (GPS) radio collars. As part of this study, the authors attempted to assess the accuracies of GPS (non-differentially corrected) positions under various vegetation canopies and terrain conditions with the use of a GPS ``test`` collar. The test collar was activated every twenty minutes to obtain a position location and continuously uplinked to Argos satellites to transfer position data files. They used a Telonics, Inc. uplink receiver to intercept the transmission and view the results of the collar in real time. They placed the collar on a stand equivalent to the neck height of an adult elk and then placed the stand within three different treatment categories: (1) topographical influence (canyon and mesa tops), (2) canopy influence (open and closed canopy), and (3) vegetation type influence (ponderosa pine and pinion pine-juniper). The collar was kept at each location for one hour (usually obtaining three fixes). In addition, the authors used a hand-held GPS to obtain a position of the test collar at the same time and location.

  17. Recent GPS Results at SLAC

    SciTech Connect

    Behrend, Dirk; Imfeld, Hans L.; /SLAC

    2005-08-17

    The Alignment Engineering Group (AEG) makes use of GPS technology for fulfilling part of its above ground surveying tasks at SLAC since early 2002. A base station (SLAC M40) has been set up at a central location of the SLAC campus serving both as master station for real-time kinematic (RTK) operations and as datum point for local GPS campaigns. The Leica RS500 system is running continuously and the GPS data are collected both externally (logging PC) and internally (receiver flashcard). The external logging is facilitated by a serial to Ethernet converter and an Ethernet connection at the station. Internal logging (ring buffer) is done for data security purposes. The weatherproof boxes for the instrumentation are excellent shelters against rain and wind, but do heat up considerably in sun light. Whereas the GPS receiver showed no problems, the Pacific Crest PDL 35 radio shut down several times due to overheating disrupting the RTK operations. In order to prevent heat-induced shutdowns, a protection against direct sun exposure (shading) and a constant air circulation system (ventilation) were installed. As no further shutdowns have occurred so far, it appears that the two measures successfully mended the heat problem.

  18. Precise estimation of tropospheric path delays with GPS techniques

    NASA Technical Reports Server (NTRS)

    Lichten, S. M.

    1990-01-01

    Tropospheric path delays are a major source of error in deep space tracking. However, the tropospheric-induced delay at tracking sites can be calibrated using measurements of Global Positioning System (GPS) satellites. A series of experiments has demonstrated the high sensitivity of GPS to tropospheric delays. A variety of tests and comparisons indicates that current accuracy of the GPS zenith tropospheric delay estimates is better than 1-cm root-mean-square over many hours, sampled continuously at intervals of six minutes. These results are consistent with expectations from covariance analyses. The covariance analyses also indicate that by the mid-1990s, when the GPS constellation is complete and the Deep Space Network is equipped with advanced GPS receivers, zenith tropospheric delay accuracy with GPS will improve further to 0.5 cm or better.

  19. GPS and GPRS Based Telemonitoring System for Emergency Patient Transportation.

    PubMed

    Satyanarayana, K; Sarma, A D; Sravan, J; Malini, M; Venkateswarlu, G

    2013-01-01

    Telemonitoring during the golden hour of patient transportation helps to improve medical care. Presently there are different physiological data acquisition and transmission systems using cellular network and radio communication links. Location monitoring systems and video transmission systems are also commercially available. The emergency patient transportation systems uniquely require transmission of data pertaining to the patient, vehicle, time of the call, physiological signals (like ECG, blood pressure, a body temperature, and blood oxygen saturation), location information, a snap shot of the patient, and voice. These requirements are presently met by using separate communication systems for voice, physiological data, and location that result in a lot of inconvenience to the technicians, maintenance related issues, in addition to being expensive. This paper presents design, development, and implementation of such a telemonitoring system for emergency patient transportation employing ARM 9 processor module. This system is found to be very useful for the emergency patient transportation being undertaken by organizations like the Emergency Management Research Institute (EMRI). PMID:27019844

  20. GPS and GPRS Based Telemonitoring System for Emergency Patient Transportation

    PubMed Central

    Satyanarayana, K.; Sarma, A. D.; Sravan, J.; Malini, M.; Venkateswarlu, G.

    2013-01-01

    Telemonitoring during the golden hour of patient transportation helps to improve medical care. Presently there are different physiological data acquisition and transmission systems using cellular network and radio communication links. Location monitoring systems and video transmission systems are also commercially available. The emergency patient transportation systems uniquely require transmission of data pertaining to the patient, vehicle, time of the call, physiological signals (like ECG, blood pressure, a body temperature, and blood oxygen saturation), location information, a snap shot of the patient, and voice. These requirements are presently met by using separate communication systems for voice, physiological data, and location that result in a lot of inconvenience to the technicians, maintenance related issues, in addition to being expensive. This paper presents design, development, and implementation of such a telemonitoring system for emergency patient transportation employing ARM 9 processor module. This system is found to be very useful for the emergency patient transportation being undertaken by organizations like the Emergency Management Research Institute (EMRI). PMID:27019844

  1. The REFSAT approach to low-cost GPS terminals

    NASA Technical Reports Server (NTRS)

    Sennott, J. W.; Choudhury, A. K.; Taylor, R. E.

    1979-01-01

    A concept utilizing a geostationary reference satellite (REFSAT) that broadcasts navigation aiding signals to low cost civil user terminals which employ the constellation of 24 NAVSTAR Global Positioning System (GPS) satellites for position determination is described. The signal acquisition, tracking and position fixing properties of such low cost, dual channel, L-band, civil user receiver designed to receive both GPS navigation and REFSAT navigation aiding signals is presented. REFSAT reduces the cost of user equipment.

  2. A Self-Tuning Kalman Filter for Autonomous Navigation using the Global Positioning System (GPS)

    NASA Technical Reports Server (NTRS)

    Truong, S. H.

    1999-01-01

    Most navigation systems currently operated by NASA are ground-based, and require extensive support to produce accurate results. Recently developed systems that use Kalman filter and GPS data for orbit determination greatly reduce dependency on ground support, and have potential to provide significant economies for NASA spacecraft navigation. These systems, however, still rely on manual tuning from analysts. A sophisticated neuro-fuzzy component fully integrated with the flight navigation system can perform the self-tuning capability for the Kalman filter and help the navigation system recover from estimation errors in real time.

  3. A simple method to improve autonomous GPS positioning for tractors.

    PubMed

    Gomez-Gil, Jaime; Alonso-Garcia, Sergio; Gómez-Gil, Francisco Javier; Stombaugh, Tim

    2011-01-01

    Error is always present in the GPS guidance of a tractor along a desired trajectory. One way to reduce GPS guidance error is by improving the tractor positioning. The most commonly used ways to do this are either by employing more precise GPS receivers and differential corrections or by employing GPS together with some other local positioning systems such as electronic compasses or Inertial Navigation Systems (INS). However, both are complex and expensive solutions. In contrast, this article presents a simple and low cost method to improve tractor positioning when only a GPS receiver is used as the positioning sensor. The method is based on placing the GPS receiver ahead of the tractor, and on applying kinematic laws of tractor movement, or a geometric approximation, to obtain the midpoint position and orientation of the tractor rear axle more precisely. This precision improvement is produced by the fusion of the GPS data with tractor kinematic control laws. Our results reveal that the proposed method effectively reduces the guidance GPS error along a straight trajectory. PMID:22163917

  4. A Simple Method to Improve Autonomous GPS Positioning for Tractors

    PubMed Central

    Gomez-Gil, Jaime; Alonso-Garcia, Sergio; Gómez-Gil, Francisco Javier; Stombaugh, Tim

    2011-01-01

    Error is always present in the GPS guidance of a tractor along a desired trajectory. One way to reduce GPS guidance error is by improving the tractor positioning. The most commonly used ways to do this are either by employing more precise GPS receivers and differential corrections or by employing GPS together with some other local positioning systems such as electronic compasses or Inertial Navigation Systems (INS). However, both are complex and expensive solutions. In contrast, this article presents a simple and low cost method to improve tractor positioning when only a GPS receiver is used as the positioning sensor. The method is based on placing the GPS receiver ahead of the tractor, and on applying kinematic laws of tractor movement, or a geometric approximation, to obtain the midpoint position and orientation of the tractor rear axle more precisely. This precision improvement is produced by the fusion of the GPS data with tractor kinematic control laws. Our results reveal that the proposed method effectively reduces the guidance GPS error along a straight trajectory. PMID:22163917

  5. An integrated GPS-FID system for airborne gas detection of pipeline right-of-ways

    SciTech Connect

    Gehue, H.L.; Sommer, P.

    1996-12-31

    Pipeline integrity, safety and environmental concerns are of prime importance in the Canadian natural gas industry. Terramatic Technology Inc. (TTI) has developed an integrated GPS/FID gas detection system known as TTI-AirTrac{trademark} for use in airborne gas detection (AGD) along pipeline right-of-ways. The Flame Ionization Detector (FID), which has traditionally been used to monitor air quality for gas plants and refineries, has been integrated with the Global Positioning System (GPS) via a 486 DX2-50 computer and specialized open architecture data acquisition software. The purpose of this technology marriage is to be able to continuously monitor air quality during airborne pipeline inspection. Event tagging from visual surveillance is used to determine an explanation of any delta line deviations (DLD). These deviations are an indication of hydrocarbon gases present in the plume that the aircraft has passed through. The role of the GPS system is to provide mapping information and coordinate data for ground inspections. The ground based inspection using a handheld multi gas detector will confirm whether or not a leak exists.

  6. Implementation of a GPS-RO data processing system for the KIAPS-LETKF data assimilation system

    NASA Astrophysics Data System (ADS)

    Kwon, H.; Kang, J.-S.; Jo, Y.; Kang, J. H.

    2015-03-01

    The Korea Institute of Atmospheric Prediction Systems (KIAPS) has been developing a new global numerical weather prediction model and an advanced data assimilation system. As part of the KIAPS package for observation processing (KPOP) system for data assimilation, preprocessing, and quality control modules for bending-angle measurements of global positioning system radio occultation (GPS-RO) data have been implemented and examined. The GPS-RO data processing system is composed of several steps for checking observation locations, missing values, physical values for Earth radius of curvature, and geoid undulation. An observation-minus-background check is implemented by use of a one-dimensional observational bending-angle operator, and tangent point drift is also considered in the quality control process. We have tested GPS-RO observations utilized by the Korean Meteorological Administration (KMA) within KPOP, based on both the KMA global model and the National Center for Atmospheric Research Community Atmosphere Model with Spectral Element dynamical core (CAM-SE) as a model background. Background fields from the CAM-SE model are incorporated for the preparation of assimilation experiments with the KIAPS local ensemble transform Kalman filter (LETKF) data assimilation system, which has been successfully implemented to a cubed-sphere model with unstructured quadrilateral meshes. As a result of data processing, the bending-angle departure statistics between observation and background show significant improvement. Also, the first experiment in assimilating GPS-RO bending angle from KPOP within KIAPS-LETKF shows encouraging results.

  7. Implementation of a GPS-RO data processing system for the KIAPS-LETKF data assimilation system

    NASA Astrophysics Data System (ADS)

    Kwon, H.; Kang, J.-S.; Jo, Y.; Kang, J. H.

    2014-11-01

    The Korea Institute of Atmospheric Prediction Systems (KIAPS) has been developing a new global numerical weather prediction model and an advanced data assimilation system. As part of the KIAPS Package for Observation Processing (KPOP) system for data assimilation, preprocessing and quality control modules for bending angle measurements of global positioning system radio occultation (GPS-RO) data have been implemented and examined. GPS-RO data processing system is composed of several steps for checking observation locations, missing values, physical values for Earth radius of curvature, and geoid undulation. An observation-minus-background check is implemented by use of a one-dimensional observational bending angle operator and tangent point drift is also considered in the quality control process. We have tested GPS-RO observations utilized by the Korean Meteorological Administration (KMA) within KPOP, based on both the KMA global model and the National Center for Atmospheric Research (NCAR) Community Atmosphere Model-Spectral Element (CAM-SE) as a model background. Background fields from the CAM-SE model are incorporated for the preparation of assimilation experiments with the KIAPS-LETKF data assimilation system, which has been successfully implemented to a cubed-sphere model with fully unstructured quadrilateral meshes. As a result of data processing, the bending angle departure statistics between observation and background shows significant improvement. Also, the first experiment in assimilating GPS-RO bending angle resulting from KPOP within KIAPS-LETKF shows encouraging results.

  8. On principles, methods and recent advances in studies towards a GPS-based control system for geodesy and geodynamics

    NASA Technical Reports Server (NTRS)

    Delikaraoglou, Demitris

    1989-01-01

    Although Very Long Baseline Interferometry (VLBI) and Satellite Laser Ranging (SLR) are becoming increasingly important tools for geodynamic studies, their future role may well be fulfilled by using alternative techniques such as those utilizing the signals from the Global Positioning System (GPS). GPS, without the full implementation of the system, already offers a favorable combination of cost and accuracy and has consistently demonstrated the capability to provide high precision densification control in the regional and local areas of the VLBI and SLR networks. This report reviews VLBI and SLR vis-a-vis GPS and outlines the capabilities and limitations of each technique and how their complementary application can be of benefit to geodetic and geodynamic operations. It demonstrates, albeit with a limited data set, that dual-frequency GPS observations and interferometric type analysis techniques make possible the modelling of the GPS orbits for several days with an accuracy of a few meters. The use of VLBI or SLR sites as fiducial stations together with refinements in the orbit determination procedures can greatly reduce the systematic errors in the GPS satellite orbits used to compute the positions of non-fiducial locations. In general, repeatability and comparison with VLBI of the GPS determined locations are of the order of between 2 parts in 10 to the 7th power and 5 parts in 10 to the 8th power for baseline lengths less than 2000 km. This report is mainly a synthesis of problems, assumptions, methods and recent advances in the studies towards the establishment of a GPS-based system for geodesy and geodynamics and is one phase in the continuing effort for the development of such a system. To some, including the author, it seems reasonable to expect within the next few years that more evidence will show GPS to be as a powerful and reliable a tool as mobile VLBI and SLR are today, but largely more economical.

  9. The March 1985 demonstration of the fiducial network concept for GPS geodesy: A preliminary report

    NASA Technical Reports Server (NTRS)

    Davidson, J. M.; Thornton, C. L.; Dixon, T. H.; Vegos, C. J.; Young, L. E.; Yunck, T. P.

    1986-01-01

    The first field tests in preparation for the NASA Global Positioning System (GPS) Caribbean Initiative were conducted in late March and Early April of 1985. The GPS receivers were located at the POLARIS Very Long Base Interferometry (VLBI) stations at Westford, Massachusetts; Richmond, Florida; and Ft. Davis, Texas; and at the Mojave, Owens Valley, and Hat Creek VLBI stations in California. Other mobile receivers were placed near Mammoth Lakes, California; Pt. Mugu, California; Austin, Texas; and Dahlgren, Virginia. These sites were equipped with a combination of GPS receiver types, including SERIES-X, TI-4100 and AFGL dual frequency receivers. The principal objectives of these tests were the demonstration of the fiducial network concept for precise GPS geodesy, the performance assessment of the participating GPS receiver types, and to conduct the first in a series of experiments to monitor ground deformation in the Mammoth Lakes-Long Valley caldera region in California. Other objectives included the testing of the water vapor radiometers for the calibration of GPS data, the development of efficient procedures for planning and coordinating GPS field exercise, the establishment of institutional interfaces for future cooperating ventures, the testing of the GPS Data Analysis Software (GIPSY, for GPS Inferred Positioning SYstem), and the establishment of a set of calibration baselines in California. Preliminary reports of the success of the field tests, including receiver performance and data quality, and on the status of the data analysis software are given.

  10. Initial Verification of the GPS-LEO Occultation Technique of Mapping the Atmosphere with the GPS-MET Experiment

    NASA Technical Reports Server (NTRS)

    Hajj, G. A.; Kursinski, E. R.; Bertiger, W. I.; Leroy, S. S.; Romans, L. J.; Schofield, J. T.

    1995-01-01

    The radio occultation technique was first used to observe Earth's atmosphere in April 1995 when a high performance Global Positioning System (GPS) receiver was placed into a low-Earth orbit. When a signal from the GPS travels through the ionosphere and the neutral atmosphere, and is received by a low-Earth orbiter (LEO) satellite, occultation data is generated. How that data is analyzed is presented.

  11. Onset, advance and withdrawal of southwest monsoon over Indian subcontinent: A study from precipitable water measurement using ground based GPS receivers

    NASA Astrophysics Data System (ADS)

    Puviarasan, N.; Sharma, A. K.; Ranalkar, Manish; Giri, R. K.

    2015-01-01

    Southwest monsoon (SWM) normally sets over Kerala by 1st June. It subsequently advances northwards and covers the entire country by 15th July. Prior knowledge of determination of date of onset of monsoon (DOM) is vital for many applications. However, accurate determination of DOM avoiding false or 'bogus' onset still remains a challenge to meteorological community. An incorrect identification of onset may lead to declaration of early onset. India Meteorological Department (IMD) has traditionally adopted an objective method to declare onset and withdrawal of monsoon based on rainfall over some specific stations in addition to wind field and Outgoing Longwave Radiation (OLR) from a bounded region. An augmentation of existing criteria of monsoon onset using high temporal resolution tropospheric precipitable water (PW) content over a station obtained through ground based GPS receiver is proposed. It has been shown that variation of PW content is an indicator of the state of monsoon and can potentially be included in operational criteria for declaring onset and withdrawal of monsoon. In the paper, we present daily variation of PW during SWM at five stations viz. Chennai, Kolkata, Guwahati, Mumbai and Delhi. The superposed epoch analysis of PW variation for 13 days with respect to arrival and withdrawal date of SWM reveals that over Kolkata at the time of arrival of monsoon the PW (mm)/SD (Standard Deviation) increases from 48.62/2.5 (day -6) to 61.4/1.9 (day 0) and on withdrawal it decreases from 48.62/4.56 (day -6) to 22.55 mm/4.0 (day 0). Similarly in Guwahati, Mumbai and Delhi the value of PW/SD increase from 53.81/4.2, 43.10/7.2 and 44.6/5.0 mm to 62.74/1.5, 62.09/1.6 and 61.88/2.3 mm and on withdrawal it reduces to 27.12/4.2, 25.94/2.6 and 20.46/4.6 mm respectively. It is also noticed that there is a sharp variation of PW from day -2 to day 0, which indicates GPS PW can be considered as a precursor for monsoon arrival and withdrawal.

  12. Evaluation of advanced sodium receiver losses during operation of the IEA/SSPS central receiver system

    SciTech Connect

    Carmona, R.; Rosa, F.; Jacobs, H.; Sanchez, M.

    1989-02-01

    This article presents the measurements and experiments conducted on the external receiver: the so-called Advanced Sodium Receiver (ASR) of the Small Solar Power Systems (SSPS) Project of the International Energy Agency (IEA) in southern Spain. The basis of this experiment was to provide loss measurements for later use in determining receiver performance. The tests to evaluate thermal losses consisted in operating the receiver with the doors open and circulating the sodium in normal and reverse flow without providing any incident power from the heliostat field (flux-off technique). In this way, total thermal losses are calculated as the energy lost by the sodium. Radiative losses have been calculated based on theoretical calculations and some results have been compared with infrared thermography measurements. Conductive losses are small and have been estimated by flux-off experiments with the receiver doors closed. Convective losses were evaluated subtracting radiative and conductive losses from the total thermal losses. Optical losses were assessed using absorptance measurements of the receiver coating. A simplified analytical model has been developed to calculate losses and ASR efficiency during operation. In spite of the method's simplicity, the results are very similar to those found by other investigators, verified simulation programs and test results.

  13. Codeless GPS systems for positioning of offshore platforms and 3D seismic surveys

    NASA Astrophysics Data System (ADS)

    MacDoran, P. F.; Miller, R. B.; Buennagel, L. A.; Fliegel, H. F.; Tanida, L.

    The Satellite Emission Range Inferred Earth Surveying (SERIES) method was originally intended for subdecimeter accuracy measurements of the crust of the earth in search of tell-tale patterns which could be exploited for research into earthquake prediction. The present paper is concerned with a specific application of the SERIES technology, taking into account high accuracy positioning related to exploration for oil and gas reserves in the offshore environment. One of the most advanced methods of exploration for hydrocarbon resources is known as 3D seismic surveying. Morgan (1983) has discussed this method, giving attention to the possible benefits of using the Global Positioning System (GPS). The present paper presents the SERIES-GPS method. It is shown that wide civil use of the Navstar is possible to levels of accuracy well beyond the Precise Positioning Service (PPS). Such a use is feasible without the DOD for Navstar codes and orbits.

  14. The Spring 1985 high precision baseline test of the JPL GPS-based geodetic system

    NASA Technical Reports Server (NTRS)

    Davidson, John M.; Thornton, Catherine L.; Stephens, Scott A.; Blewitt, Geoffrey; Lichten, Stephen M.; Sovers, Ojars J.; Kroger, Peter M.; Skrumeda, Lisa L.; Border, James S.; Neilan, Ruth E.

    1987-01-01

    The Spring 1985 High Precision Baseline Test (HPBT) was conducted. The HPBT was designed to meet a number of objectives. Foremost among these was the demonstration of a level of accuracy of 1 to 2:10 to the 7th power, or better, for baselines ranging in length up to several hundred kilometers. These objectives were all met with a high degree of success, with respect to the demonstration of system accuracy in particular. The results from six baselines ranging in length from 70 to 729 km were examined for repeatability and, in the case of three baselines, were compared to results from colocated VLBI systems. Repeatability was found to be 5:10 to the 8th power (RMS) for the north baseline coordinate, independent of baseline length, while for the east coordinate RMS repeatability was found to be larger than this by factors of 2 to 4. The GPS-based results were found to be in agreement with those from colocated VLBI measurements, when corrected for the physical separations of the VLBI and CPG antennas, at the level of 1 to 2:10 to the 7th power in all coordinates, independent of baseline length. The results for baseline repeatability are consistent with the current GPA error budget, but the GPS-VLBI intercomparisons disagree at a somewhat larger level than expected. It is hypothesized that these differences may result from errors in the local survey measurements used to correct for the separations of the GPS and VLBI antenna reference centers.

  15. Scintillation Effects on Space Shuttle GPS Data

    NASA Technical Reports Server (NTRS)

    Goodman, John L.; Kramer, Leonard

    2001-01-01

    Irregularities in ionospheric electron density result in variation in amplitude and phase of Global Positioning System (GPS) signals, or scintillation. GPS receivers tracking scintillated signals may lose carrier phase or frequency lock in the case of phase sc intillation. Amplitude scintillation can cause "enhancement" or "fading" of GPS signals and result in loss of lock. Scintillation can occur over the equatorial and polar regions and is a function of location, time of day, season, and solar and geomagnetic activity. Mid latitude regions are affected only very rarely, resulting from highly disturbed auroral events. In the spring of 1998, due to increasing concern about scintillation of GPS signals during the upcoming solar maximum, the Space Shuttle Program began to assess the impact of scintillation on Collins Miniaturized Airborne GPS Receiver (MAGR) units that are to replace Tactical Air Control and Navigation (TACAN) units on the Space Shuttle orbiters. The Shuttle Program must determine if scintillation effects pose a threat to safety of flight and mission success or require procedural and flight rule changes. Flight controllers in Mission Control must understand scintillation effects on GPS to properly diagnose "off nominal" GPS receiver performance. GPS data from recent Space Shuttle missions indicate that the signals tracked by the Shuttle MAGR manifest scintillation. Scintillation is observed as anomalous noise in velocity measurements lasting for up to 20 minutes on Shuttle orbit passes and are not accounted for in the error budget of the MAGR accuracy parameters. These events are typically coincident with latitude and local time occurrence of previously identified equatorial spread F within about 20 degrees of the magnetic equator. The geographic and seasonal history of these events from ground-based observations and a simple theoretical model, which have potential for predicting events for operational purposes, are reviewed.

  16. Sensible heat receiver for solar dynamic space power system

    NASA Technical Reports Server (NTRS)

    Perez-Davis, Marla E.; Gaier, James R.; Petrefski, Chris

    1991-01-01

    A sensible heat receiver is considered which uses a vapor grown carbon fiber-carbon (VGCF/C) composite as the thermal storage medium and which was designed for a 7-kW Brayton engine. This heat receiver stores the required energy to power the system during eclipse in the VGCF/C composite. The heat receiver thermal analysis was conducted through the Systems Improved Numerical Differencing Analyzer and Fluid Integrator (SINDA) software package. The sensible heat receiver compares well with other latent and advanced sensible heat receivers analyzed in other studies, while avoiding the problems associated with latent heat storage salts and liquid metal heat pipes. The concept also satisfies the design requirements for a 7-kW Brayton engine system. The weight and size of the system can be optimized by changes in geometry and technology advances for this new material.

  17. Sensible heat receiver for solar dynamic space power system

    NASA Technical Reports Server (NTRS)

    Perez-Davis, Marla E.; Gaier, James R.; Petrefski, Chris

    1991-01-01

    A sensible heat receiver considered in this study uses a vapor grown carbon fiber-carbon (VGCF/C) composite as the thermal storage media and was designed for a 7 kW Brayton engine. The proposed heat receiver stores the required energy to power the system during eclipse in the VGCF/C composite. The heat receiver thermal analysis was conducted through the Systems Improved Numerical Differencing Analyzer and Fluid Integrator (SINDA) software package. The sensible heat receiver compares well with other latent and advanced sensible heat receivers analyzed in other studies while avoiding the problems associated with latent heat storage salts and liquid metal heat pipes. The concept also satisfies the design requirements for a 7 kW Brayton engine system. The weight and size of the system can be optimized by changes in geometry and technology advances for this new material.

  18. COSMIC Payload in NCAR-NASPO GPS Satellite System for Severe Weather Prediction

    NASA Astrophysics Data System (ADS)

    Lai-Chen, C.

    Severe weather, such as cyclones, heavy rainfall, outburst of cold air, etc., results in great disaster all the world. It is the mission for the scientists to design a warning system, to predict the severe weather systems and to reduce the damage of the society. In Taiwan, National Satellite Project Office (NSPO) initiated ROCSAT-3 program at 1997. She scheduled the Phase I conceptual design to determine the mission for observation weather system. Cooperating with National Center of Atmospheric Research (NCAR), NSPO involved an international cooperation research and operation program to build a 32 GPS satellites system. NCAR will offer 24 GPS satellites. The total expanse will be US 100 millions. NSPO also provide US 80 millions for launching and system engineering operation. And NCAR will be responsible for Payload Control Center and Fiducial Network. The cooperative program contract has been signed by Taiwan National Science Council, Taipei Economic Cultural Office of United States and American Institute in Taiwan. One of the payload is COSMIC, Constellation Observation System for Meteorology, Ionosphere and Climate. It is a GPS meteorology instrument system. The system will observe the weather information, e. g. electron density profiles, horizontal and vertical TEC and CFT scintillation and communication outage maps. The mission is to obtain the weather data such as vertical temperature profiles, water vapor distribution and pressure distribution over the world for global weather forecasting, especially during the severe weather period. The COSMIC Conference held on November, 1998. The export license was also issued by Department of Commerce of Unites States at November, 1998. Recently, NSPO begun to train their scientists to investigate the system. Scientists simulate the observation data to combine the existing routine satellite infrared cloud maps, radar echo and synoptic weather analysis for severe weather forecasting. It is hopeful to provide more accurate

  19. Design and flight test of a differential GPS/inertial navigation system for approach/landing guidance

    NASA Technical Reports Server (NTRS)

    Vallot, Lawrence; Snyder, Scott; Schipper, Brian; Parker, Nigel; Spitzer, Cary

    1991-01-01

    NASA-Langley has conducted a flight test program evaluating a differential GPS/inertial navigation system's (DGPS/INS) utility as an approach/landing aid. The DGPS/INS airborne and ground components are based on off-the-shelf transport aircraft avionics, namely a global positioning/inertial reference unit (GPIRU) and two GPS sensor units (GPSSUs). Systematic GPS errors are measured by the ground GPSSU and transmitted to the aircraft GPIRU, allowing the errors to be eliminated or greatly reduced in the airborne equipment. Over 120 landings were flown; 36 of these were fully automatic DGPS/INS landings.

  20. ProSEDS Telemetry System Utilization of GPS Position Data for Transmitter Cycling

    NASA Technical Reports Server (NTRS)

    Kennedy, Paul; Sims, Herb

    2000-01-01

    NASA Marshall Space Flight Center will launch the Propulsive Small Expendable Deployer System (ProSEDS) space experiment in late 2000. ProSEDS will demonstrate the use of an electrodynamic tether propulsion system and will utilize a conducting wire tether to generate limited spacecraft power. This paper will provide an overview of the ProSEDS mission and will discuss the design, development and test of the spacecraft telemetry system which utilizes a custom designed GPS subsystem to determine spacecraft position relative to ground station location and to control transmitter on/off cycling based on spacecraft state vector and ground station visibility.

  1. Low cost airborne microwave landing system receiver, task 3

    NASA Technical Reports Server (NTRS)

    Hager, J. B.; Vancleave, J. R.

    1979-01-01

    Work performed on the low cost airborne Microwave Landing System (MLS) receiver is summarized. A detailed description of the prototype low cost MLS receiver is presented. This detail includes block diagrams, schematics, board assembly drawings, photographs of subassemblies, mechanical construction, parts lists, and microprocessor software. Test procedures are described and results are presented.

  2. Digital image georeferencing from a multiple camera system by GPS/INS

    NASA Astrophysics Data System (ADS)

    Mostafa, Mohamed M. R.; Schwarz, Klaus-Peter

    In this paper, the development and testing of an airborne fully digital multi-sensor system for digital mapping data acquisition is presented. The system acquires two streams of data, namely, navigation (georeferencing) data and imaging data. The navigation data are obtained by integrating an accurate strapdown inertial navigation system with a differential GPS system (DGPS). The imaging data are acquired by two low-cost digital cameras, configured in such a way so as to reduce their geometric limitations. The two cameras capture strips of overlapping nadir and oblique images. The GPS/INS-derived trajectory contains the full translational and rotational motion of the carrier aircraft. Thus, image exterior orientation information is extracted from the trajectory, during post-processing. This approach eliminates the need for ground control (GCP) when computing 3D positions of objects that appear in the field of view of the system imaging component. Two approaches for calibrating the system are presented, namely, terrestrial calibration and in-flight calibration. Test flights were conducted over the campus of The University of Calgary. Testing the system showed that best ground point positioning accuracy at 1:12,000 average image scale is 0.2 m (RMS) in easting and northing and 0.3 m (RMS) in height. Preliminary results indicate that major applications of such a system in the future are in the field of digital mapping, at scales of 1:5000 and smaller, and in the generation of digital elevation models for engineering applications.

  3. Operational GPS Imaging System at Multiple Scales for Earth Science and Monitoring of Geohazards

    NASA Astrophysics Data System (ADS)

    Blewitt, Geoffrey; Hammond, William; Kreemer, Corné

    2016-04-01

    Toward scientific targets that range from slow deep Earth processes to geohazard rapid response, our operational GPS data analysis system produces smooth, yet detailed maps of 3-dimensional land motion with respect to our Earth's center of mass at multiple spatio-temporal scales with various latencies. "GPS Imaging" is implemented operationally as a back-end processor to our GPS data processing facility, which uses JPL's GIPSY OASIS II software to produce positions from 14,000 GPS stations in ITRF every 5 minutes, with coordinate precision that gradually improves as latency increases upward from 1 hour to 2 weeks. Our GPS Imaging system then applies sophisticated signal processing and image filtering techniques to generate images of land motion covering our Earth's continents with high levels of robustness, accuracy, spatial resolution, and temporal resolution. Techniques employed by our GPS Imaging system include: (1) similarity transformation of polyhedron coordinates to ITRF with optional common-mode filtering to enhance local transient signal to noise ratio, (2) a comprehensive database of ~100,000 potential step events based on earthquake catalogs and equipment logs, (3) an automatic, robust, and accurate non-parametric estimator of station velocity that is insensitive to prevalent step discontinuities, outliers, seasonality, and heteroscedasticity; (4) a realistic estimator of velocity error bars based on subsampling statistics; (5) image processing to create a map of land motion that is based on median spatial filtering on the Delauney triangulation, which is effective at despeckling the data while faithfully preserving edge features; (6) a velocity time series estimator to assist identification of transient behavior, such as unloading caused by drought, and (7) a method of integrating InSAR and GPS for fine-scale seamless imaging in ITRF. Our system is being used to address three main scientific focus areas, including (1) deep Earth processes, (2

  4. The GPS Topex/Poseidon precise orbit determination experiment - Implications for design of GPS global networks

    NASA Technical Reports Server (NTRS)

    Lindqwister, Ulf J.; Lichten, Stephen M.; Davis, Edgar S.; Theiss, Harold L.

    1993-01-01

    Topex/Poseidon, a cooperative satellite mission between United States and France, aims to determine global ocean circulation patterns and to study their influence on world climate through precise measurements of sea surface height above the geoid with an on-board altimeter. To achieve the mission science aims, a goal of 13-cm orbit altitude accuracy was set. Topex/Poseidon includes a Global Positioning System (GPS) precise orbit determination (POD) system that has now demonstrated altitude accuracy better than 5 cm. The GPS POD system includes an on-board GPS receiver and a 6-station GPS global tracking network. This paper reviews early GPS results and discusses multi-mission capabilities available from a future enhanced global GPS network, which would provide ground-based geodetic and atmospheric calibrations needed for NASA deep space missions while also supplying tracking data for future low Earth orbiters. Benefits of the enhanced global GPS network include lower operations costs for deep space tracking and many scientific and societal benefits from the low Earth orbiter missions, including improved understanding of ocean circulation, ocean-weather interactions, the El Nino effect, the Earth thermal balance, and weather forecasting.

  5. Hybrid sodium heat pipe receivers for dish/Stirling systems

    SciTech Connect

    Laing, D.; Reusch, M.

    1997-12-31

    The design of a hybrid solar/gas heat pipe receiver for the SBP 9 kW dish/Stirling system using a United Stirling AB V160 Stirling engine and the results of on-sun testing in alternative and parallel mode will be reported. The receiver is designed to transfer a thermal power of 35 kW. The heat pipe operates at around 800 C, working fluid is sodium. Operational options are solar-only, gas augmented and gas-only mode. Also the design of a second generation hybrid heat pipe receiver currently developed under a EU-funded project, based on the experience gained with the first hybrid receiver, will be reported. This receiver is designed for the improved SPB/L. and C.-10 kW dish/Stirling system with the reworked SOLO V161 Stirling engine.

  6. A comparison between different error modeling of MEMS applied to GPS/INS integrated systems.

    PubMed

    Quinchia, Alex G; Falco, Gianluca; Falletti, Emanuela; Dovis, Fabio; Ferrer, Carles

    2013-01-01

    Advances in the development of micro-electromechanical systems (MEMS) have made possible the fabrication of cheap and small dimension accelerometers and gyroscopes, which are being used in many applications where the global positioning system (GPS) and the inertial navigation system (INS) integration is carried out, i.e., identifying track defects, terrestrial and pedestrian navigation, unmanned aerial vehicles (UAVs), stabilization of many platforms, etc. Although these MEMS sensors are low-cost, they present different errors, which degrade the accuracy of the navigation systems in a short period of time. Therefore, a suitable modeling of these errors is necessary in order to minimize them and, consequently, improve the system performance. In this work, the most used techniques currently to analyze the stochastic errors that affect these sensors are shown and compared: we examine in detail the autocorrelation, the Allan variance (AV) and the power spectral density (PSD) techniques. Subsequently, an analysis and modeling of the inertial sensors, which combines autoregressive (AR) filters and wavelet de-noising, is also achieved. Since a low-cost INS (MEMS grade) presents error sources with short-term (high-frequency) and long-term (low-frequency) components, we introduce a method that compensates for these error terms by doing a complete analysis of Allan variance, wavelet de-nosing and the selection of the level of decomposition for a suitable combination between these techniques. Eventually, in order to assess the stochastic models obtained with these techniques, the Extended Kalman Filter (EKF) of a loosely-coupled GPS/INS integration strategy is augmented with different states. Results show a comparison between the proposed method and the traditional sensor error models under GPS signal blockages using real data collected in urban roadways. PMID:23887084

  7. A Comparison between Different Error Modeling of MEMS Applied to GPS/INS Integrated Systems

    PubMed Central

    Quinchia, Alex G.; Falco, Gianluca; Falletti, Emanuela; Dovis, Fabio; Ferrer, Carles

    2013-01-01

    Advances in the development of micro-electromechanical systems (MEMS) have made possible the fabrication of cheap and small dimension accelerometers and gyroscopes, which are being used in many applications where the global positioning system (GPS) and the inertial navigation system (INS) integration is carried out, i.e., identifying track defects, terrestrial and pedestrian navigation, unmanned aerial vehicles (UAVs), stabilization of many platforms, etc. Although these MEMS sensors are low-cost, they present different errors, which degrade the accuracy of the navigation systems in a short period of time. Therefore, a suitable modeling of these errors is necessary in order to minimize them and, consequently, improve the system performance. In this work, the most used techniques currently to analyze the stochastic errors that affect these sensors are shown and compared: we examine in detail the autocorrelation, the Allan variance (AV) and the power spectral density (PSD) techniques. Subsequently, an analysis and modeling of the inertial sensors, which combines autoregressive (AR) filters and wavelet de-noising, is also achieved. Since a low-cost INS (MEMS grade) presents error sources with short-term (high-frequency) and long-term (low-frequency) components, we introduce a method that compensates for these error terms by doing a complete analysis of Allan variance, wavelet de-nosing and the selection of the level of decomposition for a suitable combination between these techniques. Eventually, in order to assess the stochastic models obtained with these techniques, the Extended Kalman Filter (EKF) of a loosely-coupled GPS/INS integration strategy is augmented with different states. Results show a comparison between the proposed method and the traditional sensor error models under GPS signal blockages using real data collected in urban roadways. PMID:23887084

  8. 80. Survivable lowfrequency communications system receiver, teletypewriter set, radio, teleprinter, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    80. Survivable low-frequency communications system receiver, teletypewriter set, radio, teleprinter, south side - Ellsworth Air Force Base, Delta Flight, Launch Control Facility, County Road CS23A, North of Exit 127, Interior, Jackson County, SD

  9. Ionospheric Profiling using GPS/MET Data

    NASA Technical Reports Server (NTRS)

    Hajj, George; Romans, Larry

    1996-01-01

    A report on ionospheric profiling using GPS and MET data is presented. A description of the GPS occultation technique, some examples of GPS/MET data products, the data processing system and a preliminary validation of ionospheric profiles is discussed.

  10. GPS Integrity Channel RTCA Working Group recommendations

    NASA Astrophysics Data System (ADS)

    Kalafus, Rudolph M.

    Recommendations made by a working group established by the Radio Technical Commission for Aeronautics are presented for the design of a wide-area broadcast service to provide indications on the status of GPS satellites. The integrity channel requirements and operational goals are outlined. Six integrity channel system concepts are considered and system design and time-to-alarm considerations are examined. The recommended system includes the broadcast of a coarse range measurement for each satellite which will enable the on-board GPS receiver to determine whether or not the navigation accuracy is within prescribed limits.

  11. 9. Water Purification System and Instrument Air Receiver Tank, view ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    9. Water Purification System and Instrument Air Receiver Tank, view to the south. The water purification system is visible in the right foreground of the photograph and the instrument air receiver tank is visible in the right background of the photograph. - Washington Water Power Clark Fork River Cabinet Gorge Hydroelectric Development, Powerhouse, North Bank of Clark Fork River at Cabinet Gorge, Cabinet, Bonner County, ID

  12. Solar central receiver reformer system for ammonia plants

    NASA Astrophysics Data System (ADS)

    1980-07-01

    An overview of a study to retrofit the Valley Nitrogen Producers, Inc., El Centro, California 600 ST/SD Ammonia Plant with Solar Central Receiver Technology is presented. The retrofit system consists of a solar central receiver reformer (SCRR) operating in parallel with the existing fossil fired reformer. Steam and hydrocarbon react in the catalyst filled tubes of the inner cavity receiver to form a hydrogen rich mixture which is the syngas feed for the ammonia production. The SCRR system will displace natural gas presently used in the fossil reformer combustion chamber.

  13. Observability Analysis of a MEMS INS/GPS Integration System with Gyroscope G-Sensitivity Errors

    PubMed Central

    Fan, Chen; Hu, Xiaoping; He, Xiaofeng; Tang, Kanghua; Luo, Bing

    2014-01-01

    Gyroscopes based on micro-electromechanical system (MEMS) technology suffer in high-dynamic applications due to obvious g-sensitivity errors. These errors can induce large biases in the gyroscope, which can directly affect the accuracy of attitude estimation in the integration of the inertial navigation system (INS) and the Global Positioning System (GPS). The observability determines the existence of solutions for compensating them. In this paper, we investigate the observability of the INS/GPS system with consideration of the g-sensitivity errors. In terms of two types of g-sensitivity coefficients matrix, we add them as estimated states to the Kalman filter and analyze the observability of three or nine elements of the coefficient matrix respectively. A global observable condition of the system is presented and validated. Experimental results indicate that all the estimated states, which include position, velocity, attitude, gyro and accelerometer bias, and g-sensitivity coefficients, could be made observable by maneuvering based on the conditions. Compared with the integration system without compensation for the g-sensitivity errors, the attitude accuracy is raised obviously. PMID:25171122

  14. A pilot study using global positioning systems (GPS) devices and surveys to ascertain older adults' travel patterns.

    PubMed

    Yen, Irene H; Leung, Cindy W; Lan, Mars; Sarrafzadeh, Majid; Kayekjian, Karen C; Duru, O Kenrik

    2015-04-01

    Some studies indicate that older adults lead active lives and travel to many destinations including those not in their immediate residential neighborhoods. We used global positioning system (GPS) devices to track the travel patterns of 40 older adults (mean age: 69) in San Francisco and Los Angeles. Study participants wore the GPS devices for 7 days in fall 2010 and winter 2011. We collected survey responses concurrently about travel patterns. GPS data showed a mean of four trips/day, and a mean trip distance of 7.6 km. Survey data indicated that older adults commonly made trips for four activities (e.g., volunteering, work, visiting friends) at least once each week. Older adults regularly travel outside their residential neighborhoods. GPS can document the mode of travel, the path of travel, and the destinations. Surveys can document the purpose of the travel and the impressions or experiences in the specific locations. PMID:24652872

  15. GPS-aided inertial technology and navigation-based photogrammetry for aerial mapping the San Andreas fault system

    USGS Publications Warehouse

    Sanchez, Richard D.; Hudnut, Kenneth W.

    2004-01-01

    Aerial mapping of the San Andreas Fault System can be realized more efficiently and rapidly without ground control and conventional aerotriangulation. This is achieved by the direct geopositioning of the exterior orientation of a digital imaging sensor by use of an integrated Global Positioning System (GPS) receiver and an Inertial Navigation System (INS). A crucial issue to this particular type of aerial mapping is the accuracy, scale, consistency, and speed achievable by such a system. To address these questions, an Applanix Digital Sensor System (DSS) was used to examine its potential for near real-time mapping. Large segments of vegetation along the San Andreas and Cucamonga faults near the foothills of the San Bernardino and San Gabriel Mountains were burned to the ground in the California wildfires of October-November 2003. A 175 km corridor through what once was a thickly vegetated and hidden fault surface was chosen for this study. Both faults pose a major hazard to the greater Los Angeles metropolitan area and a near real-time mapping system could provide information vital to a post-disaster response.

  16. Precise Real-Time Low-Earth-Orbiter Navigation With the Global Positioning System (GPS)

    NASA Astrophysics Data System (ADS)

    Bertiger, W.; Haines, B.; Kuang, D.; Lough, M.; Lichten, S.; Muellerschoen, R. J.; Vigue-Rodi, Y.; Wu, S.

    1999-01-01

    Technology currently is available to support real-time onboard knowledge of the position of a low Earth orbiter at the 5- to 15-m level using the civilian broadcast Global Positioning System (GPS) signal with sophisticated models and filtering techniques onboard the spacecraft. Without these techniques, the standard positioning service yields 50 to 100 m with the current level of selective availability (SA). Proposed augmentations and/or enhancements to the GPS system will make rms accuracies of from 10 centimeters to a few decimeters available to the real-time onboard user. Presently, near-real-time processing of GPS tracking data can routinely provide low-Earth-orbit determination accuracy at the level of 5 cm. Such processing systems can, in fact, be fully automated; recent results from the Jet Propulsion Laboratory (JPL), where ongoing daily processing of low Earth GPS tracking data has been undertaken for several years, are presented in this article, showing orbit determination accuracies at the sub-10-cm level. At the present time, such solutions can be produced with about a 10-h delay after real time, but recent improvements in JPL's processing system soon will enable turnaround at the 1-h level or better for such precise orbit determination. We anticipate that orbit determination at the 1-cm-accuracy level will be demonstrated, with some refinements to the current system, in the not too distant future. Continuing enhancements in the automation of data retrieval and precise orbit processing will result in continuing decreases in latency for ground-based generation of precise orbit products for Earth orbiters. Such ephemerides can be propagated slightly ahead to provide real-time knowledge. However, there are advantages to an onboard, real-time orbit-determination capability. These include unique mission requirements (military, strategic, and scientific), as well as the potential to dramatically lower navigation operations costs through the enabling of a

  17. Autonomous Integrated Receive System (AIRS) requirements definition. Volume 4: Functional specification for the prototype Automated Integrated Receive System (AIRS)

    NASA Technical Reports Server (NTRS)

    Chie, C. M.

    1984-01-01

    The functional requirements for the performance, design, and testing for the prototype Automated Integrated Receive System (AIRS) to be demonstrated for the TDRSS S-Band Single Access Return Link are presented.

  18. An improvement of the GPS buoy system for detecting tsunami at far offshore

    NASA Astrophysics Data System (ADS)

    Kato, T.; Terada, Y.; Nagai, T.; Kawaguchi, K.; Koshimura, S.; Matsushita, Y.

    2012-12-01

    We have developed a GPS buoy system for detecting a tsunami before its arrival at coasts and thereby mitigating tsunami disaster. The system was first deployed in 1997 for a short period in the Sagami bay, south of Tokyo, for basic experiments, and then deployed off Ofunato city, northeastern part of Japan, for the period 2001-2004. The system was then established at about 13km south of Cape Muroto, southwestern part of Japan, since 2004. Five tsunamis of about 10cm have been observed in these systems, including 2001 Peru earthquake (Mw8.3), 2003 Tokachi-oki earthquake (Mw8.3), 2004 Off Kii Peninsula earthquake (Mw7.4), 2010 Chile earthquake (Mw8.8), and 2011 Tohoku-Oki earthquake (Mw9.0). These experiments clearly showed that GPS buoy is capable of detecting tsunami with a few centimeter accuracy and can be monitored in near real time by applying an appropriate filter, real-time data transmission using radio and dissemination of obtained records of sea surface height changes through internet. Considering that the system is a powerful tool to monitor sea surface variations due to wind as well as tsunami, the Ministry of Land, Infrastructure, Transport and Tourism implemented the system in a part of the Nationwide Ocean Wave information network for Ports and HArbourS (NOWPHAS) system and deployed the system at 15 sites along the coasts around the Japanese Islands. The system detected the tsunami due to the 11th March 2011 Tohoku-Oki earthquake with higher than 6m of tsunami height at the site Off South Iwate (Kamaishi). The Japan Meteorological Agency that was monitoring the record updated the level of the tsunami warning to the greatest value due to the result. Currently, the GPS buoy system uses a RTK-GPS which requires a land base for obtaining precise location of the buoy by a baseline analysis. This algorithm limits the distance of the buoy to, at most, 20km from the coast as the accuracy of positioning gets much worse as the baseline distance becomes longer

  19. Solar Central Receiver Hybrid Power Systems sodium-cooled receiver concept. Final report. Volume III. Appendices

    SciTech Connect

    1980-01-01

    The overall, long term objective of the Solar Central Receiver Hybrid Power System is to identify, characterize, and ultimately demonstrate the viability and cost effectiveness of solar/fossil, steam Rankine cycle, hybrid power systems that: (1) consist of a combined solar central receiver energy source and a nonsolar energy source at a single, common site, (2) may operate in the base, intermediate, and peaking capacity modes, (3) produce the rated output independent of variations in solar insolation, (4) provide a significant savings (50% or more) in fuel consumpton, and (5) produce power at the minimum possible cost in mills/kWh. It is essential that these hybrid concepts be technically feasible and economically competitive with other systems in the near to mid-term time period (1985-1990) on a commercial scale. The program objective for Phase I is to identify and conceptually characterize solar/fossil steam Rankine cycle, commercial-scale, power plant systems that are economically viable and technically feasible. This volume contains appendices to the conceptual design and systems analysis studies gien in Volume II, Books 1 and 2. (WHK)

  20. The Effects of L2C Signal Tracking on High-Precision Carrier Phase GPS Positioning: Implications for the Next Generation of GNSS Systems

    NASA Astrophysics Data System (ADS)

    Blume, F.; Berglund, H.; Estey, L.

    2012-12-01

    In December 2005, the L2C signal was introduced to improve the accuracy, tracking and redundancy of the GPS system for civilian users. The L2C signal also provides improved SNR data when compared with the L2P(Y) legacy signal. However, GNSS network operators have been hesitant to use the new signal as it is not well determined how positions derived from L2 carrier phase measurements are affected. L2C carrier phase is in quadrature with L2P(Y); some manufacturers correct for this when logging L2C phase while others do not. In cases where both L2C and L2P(Y) are logged simultaneously, translation software must be used carefully in order to select which phase is used in positioning. Modifications were made to UNAVCO's teqc pre-processing software to eliminate confusion, however GNSS networks such as the IGS still suffer occasional data loss due to improperly configured GPS receivers or data flow routines. To date L2C analyses have been restricted to special applications such as snow depth and soil moisture using SNR data, as some high-precision data analysis packages are not compatible with L2C. We use several different methods to determine the effect that tracking and logging L2C has on carrier phase measurements and positioning for various receiver models and configurations. Twenty-four hour zero-length baseline solutions using L2 show sub- millimeter differences in mean positions for both horizontal and vertical components. Direct comparisons of the L2 phase observable from RINEX files with and without the L2C observable show sub-millicycle differences. The magnitude of the variations increased at low elevations. The behavior of the L2P(Y) phase observations or positions from a given receiver were not affected by the enabling of L2C tracking. We find that the use of the L2C-derived carrier phase in real-time applications can be disastrous in cases where receiver brands are mixed between those that correct for quadrature and those that do not (Figure 1). Until

  1. An automated test system for terahertz receiver characterization

    NASA Astrophysics Data System (ADS)

    Kuenzi, Linda C.; Groppi, Christopher E.; Wheeler, Caleb H.; Mani, Hamdi

    2014-07-01

    An automated test system was developed to characterize detectors for the Kilopixel Array Pathfinder Project (KAPPa), a 16-pixel 2D integrated heterodyne focal plane array. Although primarily designed for KAPPa, the system can be used with other instruments to automate tests that might be tedious and time-consuming by hand. Mechanical components include an adjustable structure of aluminum t-slot framing that supports a rotating chopper. Driven by a stepper motor, the wheel alternates between blackbodies at room temperature and 77 K. The cold load consists of absorbing material submerged in liquid nitrogen in an open Styrofoam cooler. Python scripts control the mechanical system, interface with receiver components, and process data. Test system operation was verified by sweeping the local oscillator frequency with a Virginia Diodes room temperature receiver. The system was then integrated with the KAPPa receiver to allow complete and automated testing of all array pixels with minimal user intervention.

  2. Estimating Effects of Multipath Propagation on GPS Signals

    NASA Technical Reports Server (NTRS)

    Byun, Sung; Hajj, George; Young, Lawrence

    2005-01-01

    Multipath Simulator Taking into Account Reflection and Diffraction (MUSTARD) is a computer program that simulates effects of multipath propagation on received Global Positioning System (GPS) signals. MUSTARD is a very efficient means of estimating multipath-induced position and phase errors as functions of time, given the positions and orientations of GPS satellites, the GPS receiver, and any structures near the receiver as functions of time. MUSTARD traces each signal from a GPS satellite to the receiver, accounting for all possible paths the signal can take, including all paths that include reflection and/or diffraction from surfaces of structures near the receiver and on the satellite. Reflection and diffraction are modeled by use of the geometrical theory of diffraction. The multipath signals are added to the direct signal after accounting for the gain of the receiving antenna. Then, in a simulation of a delay-lock tracking loop in the receiver, the multipath-induced range and phase errors as measured by the receiver are estimated. All of these computations are performed for both right circular polarization and left circular polarization of both the L1 (1.57542-GHz) and L2 (1.2276-GHz) GPS signals.

  3. Development of a GPS/INS/MAG navigation system and waypoint navigator for a VTOL UAV

    NASA Astrophysics Data System (ADS)

    Meister, Oliver; Mönikes, Ralf; Wendel, Jan; Frietsch, Natalie; Schlaile, Christian; Trommer, Gert F.

    2007-04-01

    Unmanned aerial vehicles (UAV) can be used for versatile surveillance and reconnaissance missions. If a UAV is capable of flying automatically on a predefined path the range of possible applications is widened significantly. This paper addresses the development of the integrated GPS/INS/MAG navigation system and a waypoint navigator for a small vertical take-off and landing (VTOL) unmanned four-rotor helicopter with a take-off weight below 1 kg. The core of the navigation system consists of low cost inertial sensors which are continuously aided with GPS, magnetometer compass, and a barometric height information. Due to the fact, that the yaw angle becomes unobservable during hovering flight, the integration with a magnetic compass is mandatory. This integration must be robust with respect to errors caused by the terrestrial magnetic field deviation and interferences from surrounding electronic devices as well as ferrite metals. The described integration concept with a Kalman filter overcomes the problem that erroneous magnetic measurements yield to an attitude error in the roll and pitch axis. The algorithm provides long-term stable navigation information even during GPS outages which is mandatory for the flight control of the UAV. In the second part of the paper the guidance algorithms are discussed in detail. These algorithms allow the UAV to operate in a semi-autonomous mode position hold as well an complete autonomous waypoint mode. In the position hold mode the helicopter maintains its position regardless of wind disturbances which ease the pilot job during hold-and-stare missions. The autonomous waypoint navigator enable the flight outside the range of vision and beyond the range of the radio link. Flight test results of the implemented modes of operation are shown.

  4. The application of NAVSTAR Differential GPS to civil helicopter operations

    NASA Technical Reports Server (NTRS)

    Beser, J.; Parkinson, B. W.

    1981-01-01

    Principles concerning the operation of the NAVSTAR Global Positioning Systems (GPS) are discussed. Selective availability issues concerning NAVSTAR GPS and differential GPS concepts are analyzed. Civil support and market potential for differential GPS are outlined. It is concluded that differential GPS provides a variation on the baseline GPS system, and gives an assured, uninterrupted level of accuracy for the civilian community.

  5. Financial study of commercialization of solar central receiver power systems

    NASA Astrophysics Data System (ADS)

    1981-03-01

    Commercialization requires that central receiver (CR) systems meet the economic criteria used by industry to select systems for capital ventures. Quantitative estimates are given of the investment required by government, utilities, and the manufacturing sector to meet the energy displacement goals for central receiver technology. Initial solar repowering and stand-alone electric utility plants will not have economic comparability with competitive energy sources. A major factor for this is that initial (first of a kind) heliostat costs will be high. As heliostat costs are reduced due to automated manufacturing economies, learning, and high volume production, central receiver technology will become more competitive. Under this task, several scenarios (0.1, 0.5, and 1.0 quad/y) were evaluated to determine the effect on commercial attractiveness and to determine the cost to government to bring about commercialization of solar central receivers.

  6. Airborne Digital Sensor System and GPS-aided inertial technology for direct geopositioning in rough terrain

    USGS Publications Warehouse

    Sanchez, Richard D.

    2004-01-01

    High-resolution airborne digital cameras with onboard data collection based on the Global Positioning System (GPS) and inertial navigation systems (INS) technology may offer a real-time means to gather accurate topographic map information by reducing ground control and eliminating aerial triangulation. Past evaluations of this integrated system over relatively flat terrain have proven successful. The author uses Emerge Digital Sensor System (DSS) combined with Applanix Corporation?s Position and Orientation Solutions for Direct Georeferencing to examine the positional mapping accuracy in rough terrain. The positional accuracy documented in this study did not meet large-scale mapping requirements owing to an apparent system mechanical failure. Nonetheless, the findings yield important information on a new approach for mapping in Antarctica and other remote or inaccessible areas of the world.

  7. Robust Real-Time Wide-Area Differential GPS Navigation

    NASA Technical Reports Server (NTRS)

    Yunck, Thomas P. (Inventor); Bertiger, William I. (Inventor); Lichten, Stephen M. (Inventor); Mannucci, Anthony J. (Inventor); Muellerschoen, Ronald J. (Inventor); Wu, Sien-Chong (Inventor)

    1998-01-01

    The present invention provides a method and a device for providing superior differential GPS positioning data. The system includes a group of GPS receiving ground stations covering a wide area of the Earth's surface. Unlike other differential GPS systems wherein the known position of each ground station is used to geometrically compute an ephemeris for each GPS satellite. the present system utilizes real-time computation of satellite orbits based on GPS data received from fixed ground stations through a Kalman-type filter/smoother whose output adjusts a real-time orbital model. ne orbital model produces and outputs orbital corrections allowing satellite ephemerides to be known with considerable greater accuracy than from die GPS system broadcasts. The modeled orbits are propagated ahead in time and differenced with actual pseudorange data to compute clock offsets at rapid intervals to compensate for SA clock dither. The orbital and dock calculations are based on dual frequency GPS data which allow computation of estimated signal delay at each ionospheric point. These delay data are used in real-time to construct and update an ionospheric shell map of total electron content which is output as part of the orbital correction data. thereby allowing single frequency users to estimate ionospheric delay with an accuracy approaching that of dual frequency users.

  8. Sound broadcasting satellite systems for individual reception by mobile receivers

    NASA Technical Reports Server (NTRS)

    Park, Y. H.

    1982-01-01

    In this paper, the feasibility of a multi-channel sound broadcasting satellite system for operation in a band between 0.5 and 2.0 GHz is investigated. Considered are sound broadcasting satellite systems that provide conventional FM sound broadcasting for individual receivers in a wide geographical area. Comparative weight estimation of sound broadcasting satellites is carried out for various sizes of coverage area and spacecraft antenna, and for different carrier frequencies in the band from 0.5 to 2.0 GHz. It is concluded that relatively light (1200 to about 1500 lbs) spacecraft are feasible, even with low-cost portable or mobile receiving systems.

  9. Integrated inertial navigation system/Global Positioning System (INS/GPS) for manned return vehicle autoland application

    NASA Astrophysics Data System (ADS)

    Braden, Kevin; Browning, Clint; Gelderloos, Hendrik; Smith, Fred; Marttila, Chuck

    It is noted that with the development of the International Space Station Freedom, people will permanently live in space and require routine access and an assured crew return capability in case of emergencies in space. The extended duration in space requires a manned return vehicle that is less demanding on the crew and provides an autonomous deorbit, entry, and autoland capability. The authors discuss an autoland capability with an integrated differential GPS/INS that provides the required position and velocity accuracies without the need for tactical aircraft navigation (TACAN) and Microwave Landing System (MLS) navigation aides. Simulation results are used to demonstrate the feasibility of autoland using differential GPS aided with a high-precision altimeter. This concept applies to several manned space applications, such as Assured Crew Return Vehicle (ACRV), Assured Shuttle Availability (ASA), Advanced Manned Launch System (AMLS), and National Aerospace Plane (NASP), and to unmanned return vehicles such as the Propulsion Avionics Module (P/AM).

  10. Time determination for spacecraft users of the Navstar Global Positioning System /GPS/

    NASA Technical Reports Server (NTRS)

    Grenchik, T. J.; Fang, B. T.

    1977-01-01

    Global Positioning System (GPS) navigation is performed by time measurements. A description is presented of a two body model of spacecraft motion. Orbit determination is the process of inferring the position, velocity, and clock offset of the user from measurements made of the user motion in the Newtonian coordinate system. To illustrate the effect of clock errors and the accuracy with which the user spacecraft time and orbit may be determined, a low-earth-orbit spacecraft (Seasat) as tracked by six Phase I GPS space vehicles is considered. The obtained results indicate that in the absence of unmodeled dynamic parameter errors clock biases may be determined to the nanosecond level. There is, however, a high correlation between the clock bias and the uncertainty in the gravitational parameter GM, i.e., the product of the universal gravitational constant and the total mass of the earth. It is, therefore, not possible to determine clock bias to better than 25 nanosecond accuracy in the presence of a gravitational error of one part per million.

  11. Proposed lidar receiver architecture for the CZMIL system

    NASA Astrophysics Data System (ADS)

    Payment, Andy; Feygels, Viktor; Fuchs, Eran

    2010-04-01

    The Coastal Zone Mapping and Imaging Lidar (CZMIL)1 system is a new generation airborne remote sensing system. The multi-sensor system integrates a lidar system, hyperspectral camera, digital camera, and a positioning system together to seamlessly record data over topographic and bathymetric environments. The recorded data is post-processed using data fusion algorithms to generate image products. In order to amplify the amount of information contained within the data fed to the algorithms, the architecture of the lidar receiver is designed using numerous techniques to maximize the quality of the recorded data. The receiver architecture employs commercial photomultiplier tubes operated in a logarithmic mode coupled to 10bit, 1GHz analog to digital converters. This architecture achieves sufficient dynamic range to support operating the system in both terrestrial and ocean environments. The multi-channel design of the lidar system requires the digitization of 9 channels of optical return signal data. The resulting large data volume necessitated design of a novel data reduction strategy. These important aspects of the lidar receiver's design are presented. The strategies illustrate how the receiver's architecture is designed to optimize the fidelity of the recorded data.

  12. SDR implementation of the receiver of adaptive communication system

    NASA Astrophysics Data System (ADS)

    Skarzynski, Jacek; Darmetko, Marcin; Kozlowski, Sebastian; Kurek, Krzysztof

    2016-04-01

    The paper presents software implementation of a receiver forming a part of an adaptive communication system. The system is intended for communication with a satellite placed in a low Earth orbit (LEO). The ability of adaptation is believed to increase the total amount of data transmitted from the satellite to the ground station. Depending on the signal-to-noise ratio (SNR) of the received signal, adaptive transmission is realized using different transmission modes, i.e., different modulation schemes (BPSK, QPSK, 8-PSK, and 16-APSK) and different convolutional code rates (1/2, 2/3, 3/4, 5/6, and 7/8). The receiver consists of a software-defined radio (SDR) module (National Instruments USRP-2920) and a multithread reception software running on Windows operating system. In order to increase the speed of signal processing, the software takes advantage of single instruction multiple data instructions supported by x86 processor architecture.

  13. High temperature helical tubular receiver for concentrating solar power system

    NASA Astrophysics Data System (ADS)

    Hossain, Nazmul

    In the field of conventional cleaner power generation technology, concentrating solar power systems have introduced remarkable opportunity. In a solar power tower, solar energy concentrated by the heliostats at a single point produces very high temperature. Falling solid particles or heat transfer fluid passing through that high temperature region absorbs heat to generate electricity. Increasing the residence time will result in more heat gain and increase efficiency. A novel design of solar receiver for both fluid and solid particle is approached in this paper which can increase residence time resulting in higher temperature gain in one cycle compared to conventional receivers. The helical tubular solar receiver placed at the focused sunlight region meets the higher outlet temperature and efficiency. A vertical tubular receiver is modeled and analyzed for single phase flow with molten salt as heat transfer fluid and alloy625 as heat transfer material. The result is compared to a journal paper of similar numerical and experimental setup for validating our modeling. New types of helical tubular solar receivers are modeled and analyzed with heat transfer fluid turbulent flow in single phase, and granular particle and air plug flow in multiphase to observe the temperature rise in one cyclic operation. The Discrete Ordinate radiation model is used for numerical analysis with simulation software Ansys Fluent 15.0. The Eulerian granular multiphase model is used for multiphase flow. Applying the same modeling parameters and boundary conditions, the results of vertical and helical receivers are compared. With a helical receiver, higher temperature gain of heat transfer fluid is achieved in one cycle for both single phase and multiphase flow compared to the vertical receiver. Performance is also observed by varying dimension of helical receiver.

  14. Modeling of GPS velocities across the Ganges-Brahmaputra Delta - Burma Arc oblique subduction system

    NASA Astrophysics Data System (ADS)

    Steckler, M. S.; Mondal, D. R.; Akhter, S. H.; Seeber, L.; Feng, L.; Gale, J.; Howe, M.; Masson, F.; Maurin, T.; Rangin, C.

    2014-12-01

    The Burma Arc is the northward continuation of the Sumatra-Anadaman subduction zone that gave rise to the 2004 M9.3 earthquake and tsunami. Near its northern end, it is colliding with the thick sediments of the Bengal Basin. The sediments of the Ganges-Brahmaputra Delta are folded and faulted, creating a subaerial 250-km wide accretionary prism. The deformation front is blind and reaches ½ way across the delta. Whether subduction is still occurring at this highly oblique plate boundary has been hotly debated. To investigate this, we combined our 25 continuous GPS receivers in Bangladesh with the campaign network in Myanmar, processing them together with GAMIT/GLOBK. We combined this data with 28 mostly campaign GPS sites in India (Gahalaut et al., 2012) by processing using the same IGS sites and performing a Helmert transformation to place all the data in same reference frame within ITRF2008. Published Indian plate poles yield a systematic residual for Bangladeshi sites believed to be on stable India. We estimated a new pole by combining 13 Indian stations (Mahesh et al., 2013) with 2 of our stations. Due to the rapid growth of the accretionary prism and the overthrusting by the Shillong Plateau, the Burma Arc changes shape from the backstop to the front folds. To project the GPS velocities into a profile, we have experimented with several projections that vary across the foldbelt, using the arc of the earthquakes and the topography as a guide. Strike-slip is mostly absorbed by the Sagaing and CMF faults, and some additional shear is distributed over the region. The best fitting suite of models for the shortening component yield 13-15 mm/y of shortening across the arc on a shallow-dipping megathrust. Additional shortening of ~4 mm/y is absorbed in the vicinity of the Kabaw Fault, where coverage is sparse. The dip of the megathrust and the depth of its downdip end trade off with one another in the different projections. The low range of dips of 6-10° is consistent

  15. The Inter- and Intra-Unit Variability of a Low-Cost GPS Data Logger/Receiver to Study Human Outdoor Walking in View of Health and Clinical Studies

    PubMed Central

    Abraham, Pierre; Noury-Desvaux, Bénédicte; Gernigon, Marie; Mahé, Guillaume; Sauvaget, Thomas; Leftheriotis, Georges; Le Faucheur, Alexis

    2012-01-01

    Purpose The present study evaluates the intra- and inter-unit variability of the GlobalSat® DG100 GPS data logger/receiver (DG100) when estimating outdoor walking distances and speeds. Methods Two experiments were performed using healthy subjects walking on a 400 m outdoor synthetic track. The two experiments consisted of two different outdoor prescribed walking protocols with distances ranging from 50 to 400 m. Experiment 1 examined the intra-unit variability of the DG100 (test-retest reproducibility) when estimating walking distances. Experiment 2 examined the inter-unit variability of four DG100 devices (unit to unit variability) when estimating walking distances and speeds. Results The coefficient of variation [95% confidence interval], for the reliability of estimating walking distances, was 2.8 [2.5–3.2] %. The inter-unit variability among the four DG100 units tested ranged from 2.8 [2.5–3.2] % to 3.9 [3.5–4.4] % when estimating distances and from 2.7 [2.4–3.0] % to 3.8 [3.4–4.2] % when estimating speeds. Conclusion The present study indicates that the DG100, an economical and convenient GPS data logger/receiver, can be reliably used to study human outdoor walking activities in unobstructed conditions. This device let facilitate the use of GPS in studies of health and disease. PMID:22363623

  16. Aircraft landing using GPS

    NASA Astrophysics Data System (ADS)

    Lawrence, David Gary

    The advent of the Global Positioning System (GPS) is revolutionizing the field of navigation. Commercial aviation has been particularly influenced by this worldwide navigation system. From ground vehicle guidance to aircraft landing applications, GPS has the potential to impact many areas of aviation. GPS is already being used for non-precision approach guidance; current research focuses on its application to more critical regimes of flight. To this end, the following contributions were made: (1) Development of algorithms and a flexible software architecture capable of providing real-time position solutions accurate to the centimeter level with high integrity. This architecture was used to demonstrate 110 automatic landings of a Boeing 737. (2) Assessment of the navigation performance provided by two GPS-based landing systems developed at Stanford, the Integrity Beacon Landing System, and the Wide Area Augmentation System. (3) Preliminary evaluation of proposed enhancements to traditional techniques for GPS positioning, specifically, dual antenna positioning and pseudolite augmentation. (4) Introduction of a new concept for positioning using airport pseudolites. The results of this research are promising, showing that GPS-based systems can potentially meet even the stringent requirements of a Category III (zero visibility) landing system. Although technical and logistical hurdles still exist, it is likely that GPS will soon provide aircraft guidance in all phases of flight, including automatic landing, roll-out, and taxi.

  17. INS/GPS/LiDAR Integrated Navigation System for Urban and Indoor Environments Using Hybrid Scan Matching Algorithm

    PubMed Central

    Gao, Yanbin; Liu, Shifei; Atia, Mohamed M.; Noureldin, Aboelmagd

    2015-01-01

    This paper takes advantage of the complementary characteristics of Global Positioning System (GPS) and Light Detection and Ranging (LiDAR) to provide periodic corrections to Inertial Navigation System (INS) alternatively in different environmental conditions. In open sky, where GPS signals are available and LiDAR measurements are sparse, GPS is integrated with INS. Meanwhile, in confined outdoor environments and indoors, where GPS is unreliable or unavailable and LiDAR measurements are rich, LiDAR replaces GPS to integrate with INS. This paper also proposes an innovative hybrid scan matching algorithm that combines the feature-based scan matching method and Iterative Closest Point (ICP) based scan matching method. The algorithm can work and transit between two modes depending on the number of matched line features over two scans, thus achieving efficiency and robustness concurrently. Two integration schemes of INS and LiDAR with hybrid scan matching algorithm are implemented and compared. Real experiments are performed on an Unmanned Ground Vehicle (UGV) for both outdoor and indoor environments. Experimental results show that the multi-sensor integrated system can remain sub-meter navigation accuracy during the whole trajectory. PMID:26389906

  18. INS/GPS/LiDAR Integrated Navigation System for Urban and Indoor Environments Using Hybrid Scan Matching Algorithm.

    PubMed

    Gao, Yanbin; Liu, Shifei; Atia, Mohamed M; Noureldin, Aboelmagd

    2015-01-01

    This paper takes advantage of the complementary characteristics of Global Positioning System (GPS) and Light Detection and Ranging (LiDAR) to provide periodic corrections to Inertial Navigation System (INS) alternatively in different environmental conditions. In open sky, where GPS signals are available and LiDAR measurements are sparse, GPS is integrated with INS. Meanwhile, in confined outdoor environments and indoors, where GPS is unreliable or unavailable and LiDAR measurements are rich, LiDAR replaces GPS to integrate with INS. This paper also proposes an innovative hybrid scan matching algorithm that combines the feature-based scan matching method and Iterative Closest Point (ICP) based scan matching method. The algorithm can work and transit between two modes depending on the number of matched line features over two scans, thus achieving efficiency and robustness concurrently. Two integration schemes of INS and LiDAR with hybrid scan matching algorithm are implemented and compared. Real experiments are performed on an Unmanned Ground Vehicle (UGV) for both outdoor and indoor environments. Experimental results show that the multi-sensor integrated system can remain sub-meter navigation accuracy during the whole trajectory. PMID:26389906

  19. Tropospheric corrections to GPS measurements using locally measured meteorological parameters compared with general tropospheric corrections

    NASA Technical Reports Server (NTRS)

    Kirchner, D.; Lentz, C.; Ressler, H.

    1994-01-01

    At the Technical University Graz (TUG), Austria, the Global Positioning System (GPS) has been used for time transfer purposes since the early 80's and from that time on local meteorological parameters have been recorded together with each measurement (satellite track). The paper compares the tropospheric corrections (delays) obtained from models usually employed in GPS receivers and those using locally measured meteorological parameters.

  20. GPS Data Analysis for Earth Orientation at the Jet Propulsion Laboratory

    NASA Technical Reports Server (NTRS)

    Zumberge, J.; Webb, F.; Lindqwister, U.; Lichten, S.; Jefferson, D.; Ibanez-Meier, R.; Heflin, M.; Freedman, A.; Blewitt, G.

    1994-01-01

    Beginning June 1992 and continuing indefinitely as part of our contribution to FLINN (Fiducial Laboratories for an International Natural Science Network), DOSE (NASA's Dynamics of the Solid Earth Program), and the IGS (International GPS Geodynamics Service), analysts at the Jet Propulsion Laboratory (JPL) have routinely been reducing data from a globally-distributed network of Rogue Global Positioning System (GPS) receivers.

  1. Solar central receiver reformer system for ammonia plants

    NASA Astrophysics Data System (ADS)

    1980-07-01

    Details of the conceptual design, economic analysis, and development plan for a solar central receiver system for retrofitting the Valley Nitrogen Producers, Inc., El Centro, California 600 ST/SD Ammonia Plant are presented. The retrofit system consists of a solar central receiver reformer (SCRR) operating in parallel with the existing fossil fired reformer. Steam and hydrocarbon react in the catalyst filled tubes of the inner cavity receiver to form a hydrogen rich mixture which is the syngas feed for the ammonia production. The SCRR system displaces natural gas presently used in the fossil reformer combustion chamber. The solar reformer retrofit system characteristics and its interface with the existing plant are simple, incorporating state of the art components with proven technology. A northfield composed of one thousand forty second generation heliostats provides solar energy to the receiver which is positioned on top of a 90 meter high steel tower. The overall economics of this system can provide over 20% discount cash flow rate of return with proper investment and market conditions.

  2. Towards evaluating the intensity of convective systems by using GPS radio occultation profiles

    NASA Astrophysics Data System (ADS)

    Biondi, Riccardo; Steiner, Andrea K.; Kirchengast, Gottfried

    2015-04-01

    Deep convective systems, also more casually often just called storms, are destructive weather phenomena causing every year many deaths, injuries and damages and accounting for major economic losses in several countries. The number and intensity of such phenomena increased over the last decades in some areas of the globe, including Europe. Damages are mostly caused by strong winds and heavy rain and these parameters are strongly connected to the structure of the storm. Convection over land is usually stronger and deeper than over the ocean and some convective systems, known as supercells, also develop tornadoes through processes which are still mostly unclear. The intensity forecast and monitoring of convective systems is one of the major challenges for meteorology because in-situ measurements during extreme events are too sparse or not reliable and most ongoing satellite missions do not provide suitable time/space coverage. With this study we propose a new method for detecting the convection intensity in terms of rain rate and surface wind speed by using meteorological surface measurements in combination with atmospheric profiles from Global Positioning System (GPS) radio occultation observations, which are available in essentially all weather conditions and with global coverage. The analysis of models indicated a relationship between the cloud top altitude and the intensity of a storm. We thus use GPS radio occultation bending angle profiles for detecting the storm's cloud top altitude and we correlate this value to the rain rate and wind speed measured by meteorological station networks in two different regions, the WegenerNet climate station network (South-Eastern Styria, Austria) and the Atmospheric Radiation Measurement site (ARM, Southern Great Plains, USA), respectively. The results show a good correlation between the cloud top altitude and the maximum rain rate in the monitored areas, while this is not found for maximum wind speed. We conclude from this

  3. Optimal on-airport monitoring of the integrity of GPS-based landing systems

    NASA Astrophysics Data System (ADS)

    Xie, Gang

    2004-11-01

    The Global Positioning System (GPS) is a satellite-based radio navigation system. The Local Area Augmentation System (LAAS) is a version of Differential GPS (DGPS) designed to reliably support aircraft precision approaches. The Integrity Monitor Testbed (IMT) is a prototype of the LAAS Ground Facility (LGF) that is used to evaluate whether the LGF can meet system integrity requirements. To insure high integrity, the IMT has a variety of monitors to detect all possible failures. It also contains a failure-handling logic, known as Executive Monitoring (EXM), to exclude faulty measurements and recover once the failure disappears. Spatial ionospheric gradients are major threats to the LAAS. One focus of this thesis is exploring methods to quickly detect ionospheric gradients given the required low probability of false alarms. The first part of the thesis introduces GPS, LAAS, and the IMT and explains the algorithms and functionalities of IMT integrity monitors in detail. It then analyzes the failure responses of the integrity monitors under the most general measurement failure model. This analysis not only qualitatively maps the integrity monitors into the entire failure space, but also provides a tool to quantitatively compare the performance of different integrity monitors. In addition, the analysis examines the limitations of the existing monitors in detecting small but hazardous ionospheric gradients. The divergence Cumulative Sum (CUSUM) method is then derived and assessed. It can reduce the time required to detect marginal ionospheric gradients by about 30%. With the divergence CUSUM method implemented in the IMT, system integrity and performance are greatly improved. Different monitors can respond to the same failures. The last part of this thesis shows that the combination of these different monitors can detect certain failures more quickly than any individual monitor. This idea leads to a new method, called failure-specific testing, which can significantly

  4. Dual RF Astrodynamic GPS Orbital Navigator Satellite

    NASA Technical Reports Server (NTRS)

    Kanipe, David B.; Provence, Robert Steve; Straube, Timothy M.; Reed, Helen; Bishop, Robert; Lightsey, Glenn

    2009-01-01

    Dual RF Astrodynamic GPS Orbital Navigator Satellite (DRAGONSat) will demonstrate autonomous rendezvous and docking (ARD) in low Earth orbit (LEO) and gather flight data with a global positioning system (GPS) receiver strictly designed for space applications. ARD is the capability of two independent spacecraft to rendezvous in orbit and dock without crew intervention. DRAGONSat consists of two picosatellites (one built by the University of Texas and one built by Texas A and M University) and the Space Shuttle Payload Launcher (SSPL); this project will ultimately demonstrate ARD in LEO.

  5. Multi-user satellite communications system using an innovative compressive receiver

    NASA Technical Reports Server (NTRS)

    Staples, Edward J.

    1992-01-01

    There is a need for an onboard simultaneous multi-channel demodulation system for a satellite communications system. Studies indicate that Convolve Multiply Convolve (CMC) filtering with surface acoustic wave (SAW) dispersive delay lines will eliminate the necessity of onboard satellite channelized filters of complex fourier transform processors. The reason for choosing the CMC technique is its ability to perform Fourier transformations in a shorter time with less space and power consumption than digital Fourier transform processors. Each ground terminal in this multi-users communications system is remotely located and operates independently; hence, a method of synchronizing the transmission of these users is presented which utilizes the existing Global Positioning System (GPS) system. Each ground user is equipped with a low cost ground terminal that has a synchronization subsystem attached to it. The system design of an onboard Multi-channel Receiver and Demodulator utilizes Quadrature Phase Shift Keying (QPSK) as the modulation technique. This technique provides the best figure of merit, i.e., the lowest transmitter power requirement per communication channel.

  6. Sea Ice Remote Sensing Using Surface Reflected GPS Signals

    NASA Technical Reports Server (NTRS)

    Komjathy, Attila; Maslanik, James; Zavorotny, Valery U.; Axelrad, Penina; Katzberg, Stephen J.

    2000-01-01

    This paper describes a new research effort to extend the application of Global Positioning System (GPS) signal reflections, received by airborne instruments, to cryospheric remote sensing. Our experimental results indicate that reflected GPS signals have potential to provide information on the presence and condition of sea and freshwater ice as well as the freeze/thaw state of frozen ground. In this paper we show results from aircraft experiments over the ice pack near Barrow, Alaska indicating correlation between forward-scattered GPS returns and RADARSAT backscattered measurements.

  7. Evaluation of GPS Coverage for the X-33 Michael-6 Trajectory

    NASA Technical Reports Server (NTRS)

    Lundberg, John B.

    1998-01-01

    The onboard navigational system for the X-33 test flights will be based on the use of measurements collected from the Embedded Global Positioning System (GPS)/INS system. Some of the factors which will affect the quality of the GPS contribution to the navigational solution will be the number of pseudorange measurements collected at any instant in time, the distribution of the GPS satellites within the field of view, and the inherent noise level of the GPS receiver. The distribution of GPS satellites within the field of view of the receiver's antenna will depend on the receiver's position, the time of day, pointing direction of the antenna, and the effective cone angle of the antenna. The number of pseudorange measurements collected will depend upon these factors as well as the time required to lock onto a GPS satellite signal once the GPS satellite comes into the field of view of the antenna and the number of available receiver channels. The objective of this study is to evaluate the GPS coverage resulting from the proposed antenna pointing directions, the proposed antenna cone angles, and the effects due to the time of day for the X-33 Michael-6 trajectory from launch at Edwards AFB, California, to the start of the Terminal Area Energy Management (TAEM) phase on approach to Michael AAF, Utah.

  8. Snow Depth with GPS: Case Study from Minnesota 2010-2011

    NASA Astrophysics Data System (ADS)

    Bilich, A. L.; Slater, A. G.; Larson, K. M.

    2011-12-01

    Although originally designed to enable accurate positioning and time transfer, the Global Positioning System (GPS) has also proved useful for remote sensing applications. In this study, GPS signals are used to measure snow depth via GPS interferometric reflectometry (GPS-IR). In GPS-IR, a GPS antenna receives the desired direct signal as well as an indirect signal which reflects off of the ground or snow surface. These two signals interfere, and the composite signal recorded by the GPS receiver can be post-processed to yield the distance between the antenna and the reflecting surface, that is, distance to the snow surface. We present the results of a new snow depth product for the state of Minnesota over the winter of 2010-2011. Although single-station examples of GPS snow depth measurements can be found in the literature, this is one of the first studies to compute GPS snow depth over a large regional-scale network. We chose Minnesota because the state Department of Transportation runs a network of continuously operating reference stations (CORS) with many desired characteristics: freely available data, good GPS station distribution with good proximity to COOP weather stations, GPS stations located adjacent to farm fields with few sky obstructions, and receiver models known to have sufficient data quality for GPS-IR. GPS-IR with CORS has many advantages over traditional snow depth measurements. First, because we leverage existing CORS, no new equipment installations are required and data are freely available via the Internet. Second, GPS-IR with CORS measures a large area, approximately 100 m2 around the station and 20 m2 per satellite. We present snow depth results for over 30 GPS stations distributed across the state. We compare the GPS-IR snow depth product to COOP observations and SNODAS modeled estimates. GPS-IR snow depth is one of the few independent data sources available for assessment of SNODAS. Ideally snow depth via GPS-IR will be available for

  9. Potential GPS user architecture for the NASA Space Station based on Landsat 4/5 experience

    NASA Technical Reports Server (NTRS)

    Korenstein, David A.

    1987-01-01

    A Landsat 4/5 GPS system is described which uses an inertial reference attitude control system and precision real-time ephemeris generation to achieve precision earth pointing. The system has application to the validation of the use of GPS for the low earth orbit navigation of the Space Station. The present system consists of a receiver/processor assembly (R/PA), an L-band GPS antenna, a precision oscillator, and the Landsat computer. The R/PA is integrated with a GPS receiver which selects, acquires, tracks, times, and decodes navigation signals from GPS satellites in order to derive ephemerides. Ephemeris estimates were found to be accurate to better than 50 meters.

  10. A heat receiver design for solar dynamic space power systems

    NASA Technical Reports Server (NTRS)

    Baker, Karl W.; Dustin, Miles O.; Crane, Roger

    1990-01-01

    An advanced heat pipe receiver designed for a solar dynamic space power system is described. The power system consists of a solar concentrator, solar heat receiver, Stirling heat engine, linear alternator and waste heat radiator. The solar concentrator focuses the sun's energy into a heat receiver. The engine and alternator convert a portion of this energy to electric power and the remaining heat is rejected by a waste heat radiator. Primary liquid metal heat pipes transport heat energy to the Stirling engine. Thermal energy storage allows this power system to operate during the shade portion of an orbit. Lithium fluoride/calcium fluoride eutectic is the thermal energy storage material. Thermal energy storage canisters are attached to the midsection of each heat pipe. The primary heat pipes pass through a secondary vapor cavity heat pipe near the engine and receiver interface. The secondary vapor cavity heat pipe serves three important functions. First, it smooths out hot spots in the solar cavity and provides even distribution of heat to the engine. Second, the event of a heat pipe failure, the secondary heat pipe cavity can efficiently transfer heat from other operating primary heat pipes to the engine heat exchanger of the defunct heat pipe. Third, the secondary heat pipe vapor cavity reduces temperature drops caused by heat flow into the engine. This unique design provides a high level of reliability and performance.

  11. Note: Optical receiver system for 152-channel magnetoencephalography

    NASA Astrophysics Data System (ADS)

    Kim, Jin-Mok; Kwon, Hyukchan; Yu, Kwon-kyu; Lee, Yong-Ho; Kim, Kiwoong

    2014-11-01

    An optical receiver system composing 13 serial data restore/synchronizer modules and a single module combiner converted optical 32-bit serial data into 32-bit synchronous parallel data for a computer to acquire 152-channel magnetoencephalography (MEG) signals. A serial data restore/synchronizer module identified 32-bit channel-voltage bits from 48-bit streaming serial data, and then consecutively reproduced 13 times of 32-bit serial data, acting in a synchronous clock. After selecting a single among 13 reproduced data in each module, a module combiner converted it into 32-bit parallel data, which were carried to 32-port digital input board in a computer. When the receiver system together with optical transmitters were applied to 152-channel superconducting quantum interference device sensors, this MEG system maintained a field noise level of 3 fT/√Hz @ 100 Hz at a sample rate of 1 kSample/s per channel.

  12. Note: Optical receiver system for 152-channel magnetoencephalography

    SciTech Connect

    Kim, Jin-Mok; Kwon, Hyukchan; Yu, Kwon-kyu; Lee, Yong-Ho; Kim, Kiwoong

    2014-11-15

    An optical receiver system composing 13 serial data restore/synchronizer modules and a single module combiner converted optical 32-bit serial data into 32-bit synchronous parallel data for a computer to acquire 152-channel magnetoencephalography (MEG) signals. A serial data restore/synchronizer module identified 32-bit channel-voltage bits from 48-bit streaming serial data, and then consecutively reproduced 13 times of 32-bit serial data, acting in a synchronous clock. After selecting a single among 13 reproduced data in each module, a module combiner converted it into 32-bit parallel data, which were carried to 32-port digital input board in a computer. When the receiver system together with optical transmitters were applied to 152-channel superconducting quantum interference device sensors, this MEG system maintained a field noise level of 3 fT/√Hz @ 100 Hz at a sample rate of 1 kSample/s per channel.

  13. Testing of CMA-2000 Microwave Landing System (MLS) airborne receiver

    NASA Astrophysics Data System (ADS)

    Labreche, L.; Murfin, A. J.

    1989-09-01

    Microwave landing system (MLS) is a precision approach and landing guidance system which provides position information and various air to ground data. Position information is provided on a wide coverage sector and is determined by an azimuth angle measurement, an elevation angle measurement, and a range measurement. MLS performance standards and testing of the MLS airborne receiver is mainly governed by Technical Standard Order TSO-C104 issued by the Federal Aviation Administration. This TSO defines detailed test procedures for use in determining the required performance under standard and stressed conditions. It also imposes disciplines on software development and testing procedures. Testing performed on the CMA-2000 MLS receiver and methods used in its validation are described. A computer automated test system has been developed to test for compliance with RTCA/DO-177 Minimum Operation Performance Standards. Extensive software verification and traceability tests designed to ensure compliance with RTCA/DO-178 are outlined.

  14. Application of GPS for transportation related engineering surveys

    NASA Astrophysics Data System (ADS)

    Merrell, Roger L.

    1986-09-01

    The Texas State Department of Highways and Public Transportation (SDHPT) has been using GPS for over two years to establish primary geodetic reference points for engineering projects and mapping control. In accordance with a Five Year GPS Implementation Plant developed in 1982, four GPS, unmanned, automatic Regional Reference Point (RRP) stations will be installed by September 1, 1986. Five additional stations are planned as justified. Each RRP will consist of a dual frequency GPS receiver that will ultimately track the satellites continuously. Operation of the receiver, telecommunications and other station keeping chores will be handled by a microcomputer. The RRP station network will be controlled through another centrally located microcomputer which is also interfaced with a larger mainframe system. Each RRP is designed to service an area bounded by a 200 KM radius and will act as the “other” receiver for roving field units operating in a GPS differential measurement mode. In order to meet the installation schedule, early decisions are being made concerning satellite tracking rates, operational scenarios, and telecommunications to facilitate development of the basic hardware and software systems. A period of continual enhancement to hardware, software and RRP operational procedures is expected as GPS technology expands.

  15. Receiver autonomous integrity monitoring (RAIM) - Techniques, performance and potential

    NASA Technical Reports Server (NTRS)

    Farrell, James L.; Van Graas, Frank

    1991-01-01

    The goal of receiver autonomous integrity monitoring (RAIM) for the Global Positioning System (GPS) is to provide a sufficient level of navigation integrity for all phases of flight based on the signals transmitted by the GPS satellites only. Integrity requirements for airborne use of GPS are reviewed. This is followed by the description of a baseline fault detection algorithm which is shown to be capable of satisfying tentative integrity requirements. The related issue of testing the fault detection algorithm is also briefly addressed. Preliminary performance results for the baseline fault detection algorithm are presented, along with the potential of RAIM techniques for achieving GPS integrity.

  16. Present-day crustal deformation along the Magallanes-Fagnano Fault System in Tierra del Fuego from repeated GPS observations

    NASA Astrophysics Data System (ADS)

    Mendoza, L.; Perdomo, R.; Hormaechea, J. L.; Del Cogliano, D.; Fritsche, M.; Richter, A.; Dietrich, R.

    2011-03-01

    The present-day deformation of the earth crust in the Argentine part of Tierra del Fuego main island (southernmost South America) is here investigated based on repeated geodetic GPS observations. The island is traversed by the active transform boundary between the South American and Scotia tectonic plates, represented by the Magallanes-Fagnano fault system. Since 1993 a regional network comprising to date 29 GPS sites has been observed almost every year. The complete set of accumulated observations was processed using the Bernese GPS software and state-of-the-art processing strategies and models. The utilization of homogeneous GPS products resulting from a reprocessing of the global IGS network warrants a stable realization of a global reference frame. For each GPS site 3-D positions and linear velocities with error estimates were obtained. A strain analysis of the horizontal velocity components revealed the zones of major deformation activity. A 30-km-wide deformation belt centred on the main trace of the fault system was identified. This belt is bordered to the north (South America) and south (Scotia) by geodynamically stable zones, which move horizontally with a relative average velocity of 4.4 ± 0.6 (east) and -0.3 ± 0.4 (north) mm a-1. Within the deformation belt a maximum strain rate in the order of 0.25 μstrain per year has been detected. A pronounced change in the deformation style from transtension (east) to transpression (west) is observed. The area of predominating shortening of the crust coincides with a local rotation minimum and relative uplift. Throughout the period covered by the GPS observations the displacements and deformations occurred to be linear with time.

  17. Flight test evaluation of the E-systems Differential GPS category 3 automatic landing system

    NASA Technical Reports Server (NTRS)

    Kaufmann, David N.; Mcnally, B. David

    1995-01-01

    Test flights were conducted to evaluate the capability of Differential Global Positioning System (DGPS) to provide the accuracy and integrity required for International Civil Aviation Organization (ICAO) Category (CAT) III precision approach and landings. These test flights were part of a Federal Aviation Administration (FAA) program to evaluate the technical feasibility of using DGPS based technology for CAT III precision approach and landing applications. An IAI Westwind 1124 aircraft (N24RH) was equipped with DGPS receiving equipment and additional computing capability provided by E-Systems. The test flights were conducted at NASA Ames Research Center's Crows Landing Flight Facility, Crows Landing, California. The flight test evaluation was based on completing 100 approaches and landings. The navigation sensor error accuracy requirements were based on ICAO requirements for the Microwave Landing System (MLS). All of the approaches and landings were evaluated against ground truth reference data provided by a laser tracker. Analysis of these approaches and landings shows that the E-Systems DGPS system met the navigation sensor error requirements for a successful approach and landing 98 out of 100 approaches and landings, based on the requirements specified in the FAA CAT III Level 2 Flight Test Plan. In addition, the E-Systems DGPS system met the integrity requirements for a successful approach and landing or stationary trial for all 100 approaches and landings and all ten stationary trials, based on the requirements specified in the FAA CAT III Level 2 Flight Test Plan.

  18. GLORI (GLObal navigation satellite system Reflectometry Instrument): A New Airborne GNSS-R receiver for land surface applications

    NASA Astrophysics Data System (ADS)

    Motte, Erwan; Zribi, Mehrez; Fanise, Pascal

    2015-04-01

    GLORI (GLObal navigation satellite system Reflectometry Instrument) is a new receiver dedicated to the airborne measurement of surface parameters such as soil moisture and biomass above ground and sea state (wave height and direction) above oceans. The instrument is based on the PARIS concept [Martin-Neira, 1993] using both the direct and surface-reflected L-band signals from the GPS constellation as a multistatic radar source. The receiver is based on one up-looking and one down-looking dual polarization hemispherical active antennas feeding a low-cost 4-channel SDR direct down-conversion receiver tuned to the GPS L1 frequency. The raw measurements are sampled at 16.368MHz and stored as 2-bit, IQ binary files. In post-processing, GPS acquisition and tracking are performed on the direct up-looking signal while the down-looking signal is processed blindly using tracking parameters from the direct signal. The obtained direct and reflected code-correlation waveforms are the basic observables for geophysical parameters inversion. The instrument was designed to be installed aboard the ATR42 experimental aircraft from the French SAFIRE fleet as a permanent payload. The long term goal of the project is to provide real-time continuous surface information for every flight performed. The aircraft records attitude information through its Inertial Measurement Unit and a commercial GPS receiver records additional information such as estimated doppler and code phase, receiver location, satellites azimuth and elevation. A series of test flights were performed over both the Toulouse and Gulf of Lion (Mediterranean Sea) regions during the period 17-21 Nov 2014 together with the KuROS radar [Hauser et al., 2014]. Using processing methods from the literature [Egido et al., 2014], preliminary results demonstrate the instrument sensitivity to both ground and ocean surface parameters estimation. A dedicated scientific flight campaign is planned at the end of second quarter 2015 with

  19. Analyzing radio interferometric positioning systems with undersampling receivers

    NASA Astrophysics Data System (ADS)

    Shinotsuka, Marie; Wang, Yiyin; Ma, Xiaoli; Zhou, G. Tong

    2015-12-01

    Radio interferometric positioning systems are developed for localization in wireless sensor networks (WSNs), and they have the potential to yield highly accurate location information at low computational cost and implementation complexity. In the radio interferometric positioning system (RIPS), two transmitters transmit sinusoidal signals at slightly different frequencies, and two receivers pass the received signals through square-law devices to produce low-frequency differential signals. However, a squaring operation increases the noise power, leading to performance loss. To avoid this problem, a receiver for the RIPS using undersampling techniques (RIPS-u) has been proposed. In this paper, we investigate the performance of the RIPS with a square-law device (RIPS-sq) and the performance of the RIPS-u through theoretical and experimental analyses. Specifically, we compute Cramér-Rao lower bounds (CRLBs) of the range and location estimates in both systems and show that the RIPS-u has lower CRLBs than the RIPS-sq. Furthermore, we have carried out experimental tests by implementing both systems on National Instruments (NI) Universal Software Radio Peripherals (USRPs). From both the theoretical and experimental results, the effectiveness of the RIPS-u over the RIPS-sq is confirmed.

  20. A 200kW central receiver CPV system

    SciTech Connect

    Lasich, John Thomas, Ian Hertaeg, Wolfgang; Shirley, David; Faragher, Neil; Erenstrom, Neil; Carter, Sam; Cox, Brian; Zuo, Xinyi

    2015-09-28

    Raygen Resources has recently completed a Central Receiver CPV (CSPV) pilot plant in Central Victoria, Australia. The system is under final commissioning and initial operation is expected in late April 2015. The pilot demonstrates a full scale CSPV repeatable unit in a form that is representative of a commercial product and provides a test bed to prove out performance and reliability of the CSPV technology. Extensive testing of the system key components: dense array module, wireless solar powered heliostat and control system has been performed in the laboratory and on sun. Results from this key component testing are presented herein.

  1. A 200kW central receiver CPV system

    NASA Astrophysics Data System (ADS)

    Lasich, John; Thomas, Ian; Hertaeg, Wolfgang; Shirley, David; Faragher, Neil; Erenstrom, Neil; Carter, Sam; Cox, Brian; Zuo, Xinyi

    2015-09-01

    Raygen Resources has recently completed a Central Receiver CPV (CSPV) pilot plant in Central Victoria, Australia. The system is under final commissioning and initial operation is expected in late April 2015. The pilot demonstrates a full scale CSPV repeatable unit in a form that is representative of a commercial product and provides a test bed to prove out performance and reliability of the CSPV technology. Extensive testing of the system key components: dense array module, wireless solar powered heliostat and control system has been performed in the laboratory and on sun. Results from this key component testing are presented herein.

  2. GPS-Like Phasing Control of the Space Solar Power System Transmission Array

    NASA Technical Reports Server (NTRS)

    Psiaki, Mark L.

    2003-01-01

    The problem of phasing of the Space Solar Power System's transmission array has been addressed by developing a GPS-like radio navigation system. The goal of this system is to provide power transmission phasing control for each node of the array that causes the power signals to add constructively at the ground reception station. The phasing control system operates in a distributed manner, which makes it practical to implement. A leader node and two radio navigation beacons are used to control the power transmission phasing of multiple follower nodes. The necessary one-way communications to the follower nodes are implemented using the RF beacon signals. The phasing control system uses differential carrier phase relative navigation/timing techniques. A special feature of the system is an integer ambiguity resolution procedure that periodically resolves carrier phase cycle count ambiguities via encoding of pseudo-random number codes on the power transmission signals. The system is capable of achieving phasing accuracies on the order of 3 mm down to 0.4 mm depending on whether the radio navigation beacons operate in the L or C bands.

  3. A Low-Cost GPS GSM/GPRS Telemetry System: Performance in Stationary Field Tests and Preliminary Data on Wild Otters (Lutra lutra)

    PubMed Central

    Quaglietta, Lorenzo; Martins, Bruno Herlander; de Jongh, Addy; Mira, António; Boitani, Luigi

    2012-01-01

    Background Despite the increasing worldwide use of global positioning system (GPS) telemetry in wildlife research, it has never been tested on any freshwater diving animal or in the peculiar conditions of the riparian habitat, despite this latter being one of the most important habitat types for many animal taxa. Moreover, in most cases, the GPS devices used have been commercial and expensive, limiting their use in low-budget projects. Methodology/Principal Findings We have developed a low-cost, easily constructed GPS GSM/GPRS (Global System for Mobile Communications/General Packet Radio Service) and examined its performance in stationary tests, by assessing the influence of different habitat types, including the riparian, as well as water submersion and certain climatic and environmental variables on GPS fix-success rate and accuracy. We then tested the GPS on wild diving animals, applying it, for the first time, to an otter species (Lutra lutra). The rate of locations acquired during the stationary tests reached 63.2%, with an average location error of 8.94 m (SD = 8.55). GPS performance in riparian habitats was principally affected by water submersion and secondarily by GPS inclination and position within the riverbed. Temporal and spatial correlations of location estimates accounted for some variation in the data sets. GPS-tagged otters also provided accurate locations and an even higher GPS fix-success rate (68.2%). Conclusions/Significance Our results suggest that GPS telemetry is reliably applicable to riparian and even diving freshwater animals. They also highlight the need, in GPS wildlife studies, for performing site-specific pilot studies on GPS functioning as well as for taking into account eventual spatial and temporal correlation of location estimates. The limited price, small dimensions, and high performance of the device presented here make it a useful and cost-effective tool for studies on otters and other aquatic or terrestrial medium

  4. Single Cell Analysis of a Bacterial Sender-Receiver System.

    PubMed

    Ramalho, Tiago; Meyer, Andrea; Mückl, Andrea; Kapsner, Korbinian; Gerland, Ulrich; Simmel, Friedrich C

    2016-01-01

    Monitoring gene expression dynamics on the single cell level provides important information on cellular heterogeneity and stochasticity, and potentially allows for more accurate quantitation of gene expression processes. We here study bacterial senders and receivers genetically engineered with components of the quorum sensing system derived from Aliivibrio fischeri on the single cell level using microfluidics-based bacterial chemostats and fluorescence video microscopy. We track large numbers of bacteria over extended periods of time, which allows us to determine bacterial lineages and filter out subpopulations within a heterogeneous population. We quantitatively determine the dynamic gene expression response of receiver bacteria to varying amounts of the quorum sensing inducer N-3-oxo-C6-homoserine lactone (AHL). From this we construct AHL response curves and characterize gene expression dynamics of whole bacterial populations by investigating the statistical distribution of gene expression activity over time. The bacteria are found to display heterogeneous induction behavior within the population. We therefore also characterize gene expression in a homogeneous bacterial subpopulation by focusing on single cell trajectories derived only from bacteria with similar induction behavior. The response at the single cell level is found to be more cooperative than that obtained for the heterogeneous total population. For the analysis of systems containing both AHL senders and receiver cells, we utilize the receiver cells as 'bacterial sensors' for AHL. Based on a simple gene expression model and the response curves obtained in receiver-only experiments, the effective AHL concentration established by the senders and their 'sending power' is determined. PMID:26808777

  5. Single Cell Analysis of a Bacterial Sender-Receiver System

    PubMed Central

    Mückl, Andrea; Kapsner, Korbinian; Gerland, Ulrich; Simmel, Friedrich C.

    2016-01-01

    Monitoring gene expression dynamics on the single cell level provides important information on cellular heterogeneity and stochasticity, and potentially allows for more accurate quantitation of gene expression processes. We here study bacterial senders and receivers genetically engineered with components of the quorum sensing system derived from Aliivibrio fischeri on the single cell level using microfluidics-based bacterial chemostats and fluorescence video microscopy. We track large numbers of bacteria over extended periods of time, which allows us to determine bacterial lineages and filter out subpopulations within a heterogeneous population. We quantitatively determine the dynamic gene expression response of receiver bacteria to varying amounts of the quorum sensing inducer N-3-oxo-C6-homoserine lactone (AHL). From this we construct AHL response curves and characterize gene expression dynamics of whole bacterial populations by investigating the statistical distribution of gene expression activity over time. The bacteria are found to display heterogeneous induction behavior within the population. We therefore also characterize gene expression in a homogeneous bacterial subpopulation by focusing on single cell trajectories derived only from bacteria with similar induction behavior. The response at the single cell level is found to be more cooperative than that obtained for the heterogeneous total population. For the analysis of systems containing both AHL senders and receiver cells, we utilize the receiver cells as ‘bacterial sensors’ for AHL. Based on a simple gene expression model and the response curves obtained in receiver-only experiments, the effective AHL concentration established by the senders and their ‘sending power’ is determined. PMID:26808777

  6. Novel Calibration System with Sparse Wires for CMB Polarization Receivers

    NASA Astrophysics Data System (ADS)

    Tajima, O.; Nguyen, H.; Bischoff, C.; Brizius, A.; Buder, I.; Kusaka, A.

    2012-06-01

    A curl competent (also known as B-modes) in the cosmic microwave background (CMB) polarization is a smoking gun signature of the inflationary universe. To achieve better sensitivity to this faint signal, CMB polarization experiments aim to maximize the number of detector elements, resulting in a large focal plane receiver. Detector calibration of the polarization response becomes essential. It is extremely useful to be able to calibrate "simultaneously" all detectors on the large focal plane. We developed a novel calibration system that rotates a large "sparse" grid of metal wires, in front of and fully covering the field of view of the focal plane receiver. Polarized radiation is created via the reflection of ambient temperature photons from the wire surface. Since the detector has a finite beam size, the observed signal is convolved with the beam property. The intensity of the of the calibrator is reasonable (a few Kelvin or less) compared to sky temperature for typical observing conditions (˜10 K). The system played a successful role for receiver calibration of QUIET, a CMB polarization experiment located in the Atacama desert in Chile. The successful performance revealed that this system is applicable to other experiments based on different technologies, e.g. TES bolometers.

  7. Novel calibration system with sparse wires for CMB polarization receivers

    SciTech Connect

    Tajima, O.; Nguyen, H.; Bischoff, C.; Brizius, A.; Buder, I.; Kusaka, A. /Chicago U., KICP

    2011-07-01

    B-modes in the cosmic microwave background (CMB) polarization is a smoking gun signature of the inflationary universe. To achieve better sensitivity to this faint signal, CMB polarization experiments aim to maximize the number of detector elements, resulting in a large focal plane receiver. Detector calibration of the polarization response becomes essential. It is extremely useful to be able to calibrate 'simultaneously' all detectors on the large focal plane. We developed a novel calibration system that rotates a large 'sparse' grid of metal wires, in front of and fully covering the field of view of the focal plane receiver. Polarized radiation is created via the reflection of ambient temperature from the wire surface. Since the detector has a finite beam size, the observed signal is smeared according to the beam property. The resulting smeared polarized radiation has a reasonable intensity (a few Kelvin or less) compared to the sky temperature ({approx}10 K observing condition). The system played a successful role for receiver calibration of QUIET, a CMB polarization experiment located in the Atacama desert in Chile. The successful performance revealed that this system is applicable to other experiments based on different technologies, e.g. TES bolometers.

  8. Evaluating home range techniques: use of Global Positioning System (GPS) collar data from chacma baboons.

    PubMed

    Pebsworth, Paula A; Morgan, Hanna R; Huffman, Michael A

    2012-10-01

    Global Positioning System (GPS) collars have revolutionized the field of spatial ecology, but to date, few primate studies have used them. We fitted a free-ranging, semi-habituated, juvenile male chacma baboon (Papio hamadryas ursinus) with an automatic self-releasing GPS collar and tracked his movements for 359 days. The collar captured 4254 fixes out of 5719 programmed opportunities, a 74.4 % acquisition rate, suggesting that the collar effectively tracked this baboon in a variety of habitat types. Of the data points captured, 73.7 % were three-dimensional fixes, and of these fixes, 66.9 % were highly accurate, having a dilution of precision of less than four. We calculated home range using three protocols with three estimation methods: minimum convex polygon, fixed kernel-density estimation (KDE), and fixed r local convex hull. Using all data points and the 95 % contour, these methods created home range estimations ranging from 10.8 to 23.1 km(2) for this baboon troop. Our results indicate that the KDE output using all data locations most accurately represented our data set, as it created a continuous home range boundary that excluded unused areas and outlying, potentially exploratory data points while including all seven sleeping sites and a movement corridor. However, home range estimations generated from KDE varied from 15.4 to 18.8 km(2) depending on the smoothing parameter used. Our results demonstrated that the ad hoc smoothing parameter selection technique was a better method for our data set than either the least squares cross-validation or biased cross-validation techniques. Our results demonstrate the need for primatologists to develop a standardized reporting method which documents the tool, screening protocol, and smoothing parameter used in the creation of home range estimations in order to make comparisons that are meaningful. PMID:22476515

  9. Processing GPS Occultation Data To Characterize Atmosphere

    NASA Technical Reports Server (NTRS)

    Hajj, George; Kursinski, Emil; Leroy, Stephen; Lijima, Byron; de la Torre Juarez, Manuel; Romans, Larry; Ao, Chi

    2005-01-01

    GOAS [Global Positioning System (GPS) Occultation Analysis System] is a computer program that accepts signal-occultation data from GPS receivers aboard low-Earth-orbiting satellites and processes the data to characterize the terrestrial atmosphere and, in somewhat less comprehensive fashion, the ionosphere. GOAS is very robust and can be run in an unattended semi-operational processing mode. It features sophisticated retrieval algorithms that utilize the amplitudes and phases of the GPS signals. It incorporates a module that, using an assumed atmospheric refractivity profile, simulates the effects of the retrieval processing system, including the GPS receiver. GOAS utilizes the GIPSY software for precise determination of orbits as needed for calibration. The GOAS output for the Earth s troposphere and mid-to-lower stratosphere consists of high-resolution (<1 km) profiles of density, temperature, pressure, atmospheric refractivity, bending angles of signals, and water-vapor content versus altitude from the Earth s surface to an altitude of 30 km. The GOAS output for the ionosphere consists of electron-density profiles from an altitude of about 50 km to the altitude of a satellite, plus parameters related to the rapidly varying structure of the electron density, particularly in the E layer of the ionosphere.

  10. Novel receiver scheme for optical packet ultradense WDM systems

    NASA Astrophysics Data System (ADS)

    Aida, Kazuo

    2001-10-01

    We propose a scheme for reduction of cross-talk arising form stop-band rejection limitation of optical band-pas filters in a wavelength-division multiplexing receiver. Experiment confirms high selectivity of the receiver and reveals feasibility of optical packet ultra dense WDM systems spaced by several GHz. The receiver consists of optical switches at input and output ports of a fiber loop, which contains fiber delay line, tunable optical band-pass filters, an erbium-doped fiber amplifier, and an optical switch. Target packet is selected from input optical packet WDM signals by time and wavelength windows realized by the optical switches at the input and output ports of the fiber loop, and the tunable filters in the loss compensated fiber loop, respectively. The selectivity is measured by using pulsed lightwave sweep frequency, which contains 7 frequencies in 500MHz step. The results show 11dB suppression for signals 2 GH apart from the target channel after 10 circulation, and 12dB suppression for signals 1.5 GHz apart from the target channel after 18 circulation. Details of the receiver configuration, pulsed lightwave sweep frequency generator and experimental results are discussed.

  11. Method to measure the Stokes parameters of GPS signals

    NASA Astrophysics Data System (ADS)

    Benton, C. J.; Mitchell, C. N.

    2014-01-01

    As Global Positioning System (GPS) signals travel to the ground, they are affected by the medium through which they propagate. Consequently, measurements of signal amplitude and phase are used in a variety of remote sensing applications. A limitation of current receiver systems is that they do not measure polarization. While GPS signals are transmitted with right-hand circular polarization, the same cannot necessarily be said for the signal reaching the antenna, and this difference will contain further information about the propagation path. This paper describes a method for combining two GPS receivers into a device that is capable of measuring the Stokes parameters of the signal. A mathematical procedure for converting the receiver data into the Stokes parameters is derived, and the results of proof-of-concept experiments are presented.

  12. Single Frequency GPS Orbit Determination for Low Earth Orbiters

    NASA Technical Reports Server (NTRS)

    Bertiger, Willy; Wu, Sien-Chong

    1996-01-01

    A number of missions in the future are planning to use GPS for precision orbit determination. Cost considerations and receiver availability make single frequency GPS receivers attractive if the orbit accuracy requirements can be met.

  13. Architecture and performance of a real time differential GPS ground station

    NASA Technical Reports Server (NTRS)

    Turner, R. N.; Van Graas, F.; Van Dierendonck, A. J.; Hua, Q. D.

    1986-01-01

    The NAVSTAR Global Positioning System (GPS) is a satellite based navigation system that can be operated in a differential mode. The basic concept of differential GPS is to have a local ground station at a known location. The ground station continuously determines bias corrections based on the received satellite signals and transmits these corrections to local users. This allows the user to improve significantly their estimate of position. The architecture of a real time differential GPS ground station based on two STI (Stanford Telecommunications, Inc.) single-channel GPS receivers is presented. Receiver requirements are described, together with the receiver architectures. Real time operation results are presented for recent data collected from six satellites.

  14. Atmospheric Profiling using GPS Radio Occultation over the Australian and Antarctic regions

    NASA Astrophysics Data System (ADS)

    Norman, R.; Le Marshall, J.; Carter, B. A.; Kirchengast, G.; Alexander, S.; Wang, C. S.; Zhang, K.

    2014-12-01

    The space-based Global Positioning System (GPS) Radio Occultation (RO) technique is ideal for sounding the Earth's atmosphere. The GPS RO technique uses GPS receiver's on-board Low Earth Orbit (LEO) satellites to measure the received radio signals from GPS satellites. Atmospheric parameter profiles of electron density, temperature, pressure and water vapor can then be obtained using well defined and robust retrieval processes. In this study atmospheric parameter profiles were retrieved from Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) GPS RO measurements for the years 2007 to 2013 over Australia, Antarctica and their surrounding oceans. The yearly and bi-monthly tropopause height and temperature and climatic trends are investigated and co-located GPS RO and radiosonde atmospheric profiles are compared. Forecast skill scores with and without GPS RO data over the Australian and Antarctic regions are also assessed. Finally, a 3-D ray tracing technique was developed to investigate and improve the GPS RO technique. Simulated results from a tropospheric storm event on GPS RO signal propagation are investigated.

  15. Developing a Fundamental Model for an Integrated GPS/INS State Estimation System with Kalman Filtering

    NASA Technical Reports Server (NTRS)

    Canfield, Stephen

    1999-01-01

    This work will demonstrate the integration of sensor and system dynamic data and their appropriate models using an optimal filter to create a robust, adaptable, easily reconfigurable state (motion) estimation system. This state estimation system will clearly show the application of fundamental modeling and filtering techniques. These techniques are presented at a general, first principles level, that can easily be adapted to specific applications. An example of such an application is demonstrated through the development of an integrated GPS/INS navigation system. This system acquires both global position data and inertial body data, to provide optimal estimates of current position and attitude states. The optimal states are estimated using a Kalman filter. The state estimation system will include appropriate error models for the measurement hardware. The results of this work will lead to the development of a "black-box" state estimation system that supplies current motion information (position and attitude states) that can be used to carry out guidance and control strategies. This black-box state estimation system is developed independent of the vehicle dynamics and therefore is directly applicable to a variety of vehicles. Issues in system modeling and application of Kalman filtering