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1

Global digital topography mapping using a scanning radar altimeter  

NASA Technical Reports Server (NTRS)

The conceptual design of a Scanning Radar Altimeter system capable of collecting less than 300-m spatial and less than 3-m height resolution digital topography data for the entire globe, from an orbital platform, is presented. A 37-GHz frequency SRA system is used to achieve the requisite resolution while reducing antenna length in the along-track dimension. Near-global coverage in a short time period is obtained by scanning the antenna beam cross-track, in a swath of about 100 km. Attention is given to the algorithm that will be used to retrieve pixel height from the return waveform.

Elachi, C.; Im, K. E.; Li, F.; Rodriguez, E.

1987-01-01

2

Global digital topography mapping with a synthetic aperture scanning radar altimeter  

NASA Technical Reports Server (NTRS)

Global digital topography data of the land surface is of importance in a variety of geoscientific and application disciplines. Such a database, with a spatial resolution of 150 to 500 m and height accuracy of 5 m or better can be acquired from an orbiting platform using a synthetic aperture scanning radar altimeter. Near-global coverage can be achieved within 14 days from an orbiting platform in a polar or near-polar orbit.

Elachi, C.; Im, K. E.; Rodriguez, E.

1990-01-01

3

Estimating Water Slope in Amazon River Tributaries Using the Shuttle Radar Topography Mission Digital Elevation Model  

Microsoft Academic Search

Extracting river height from the Shuttle Radar Topography Mission digital elevation model (SRTM DEM) for four Amazon River tributaries found water surface elevation standard deviations of 6.16 m for the Madeira River, 7.47 m for the Purus River, 5.28 m for the Negro River, and 5.35 m for the Branco River. Standard deviations and slopes were found for the Madeira,

J. Hamski; G. Lefavour; D. Alsdorf; T. Pavelsky

2006-01-01

4

Analysis and characterization of the vertical accuracy of digital elevation models from the Shuttle Radar Topography Mission  

Microsoft Academic Search

The first near-global high-resolution digital elevation model (DEM) of the Earth has recently been released following the successful Shuttle Radar Topography Mission (SRTM) of 2000. This data set will have applications in a wide range of fields and will be especially valuable in the Earth sciences. Prior to widespread dissemination and use, it is important to acquire knowledge regarding the

Giacomo Falorni; Vanessa Teles; Enrique R. Vivoni; Rafael L. Bras; Kevin S. Amaratunga

2005-01-01

5

Estimating Water Slope in Amazon River Tributaries Using the Shuttle Radar Topography Mission Digital Elevation Model  

NASA Astrophysics Data System (ADS)

Extracting river height from the Shuttle Radar Topography Mission digital elevation model (SRTM DEM) for four Amazon River tributaries found water surface elevation standard deviations of 6.16 m for the Madeira River, 7.47 m for the Purus River, 5.28 m for the Negro River, and 5.35 m for the Branco River. Standard deviations and slopes were found for the Madeira, Purus, and Branco rivers by fitting a simple, straight line to the SRTM heights with ~1000 km of flow distance. A second order polynomial was used for the Negro River. Resulting water surface slopes are 3.63 cm/km for the Madeira, 2.83 cm/km for the Purus, and 6.95 cm/km for the Branco whereas a range in slope from 7.00 to 2.10 cm/km was found for the Negro. Using a conservative, annual minimum water slope estimate of 2 cm/km for each tributary leads to reach length requirements of 616 km for the Madiera, 747 km for the Purus, 528 km for the Negro, and 535 km for the Branco to clearly delineate slope. The Global Rain Forest Mapping project's synthetic aperture radar mosaics (GRFM SAR) provide river width. Channel width is computed at each GRFM SAR pixel along a center line obtained by thresholding the Laplacian of an image containing the distance from each channel pixel to the nearest bank pixel. For the Purus River a depth estimate of 15 m and a Manning's n of 0.03 are assumed in calculating river flow velocities using Manning's equation. Using the estimated velocity of 1.04 m/s, the calculated Purus River discharge is 8500 m3/s. state.edu/water/

Hamski, J.; Lefavour, G.; Alsdorf, D.; Pavelsky, T.

2006-12-01

6

The Shuttle Radar Topography Mission  

NASA Technical Reports Server (NTRS)

On February 22, 2000 Space Shuttle Endeavour landed at Kennedy Space Center, completing the highly successful 11-day flight of the Shuttle Radar Topography Mission (SRTM). Onboard were over 300 high-density tapes containing data for the highest resolution, most complete digital topographic map of Earth ever made. SRTM is a cooperative project between NASA and the National Imagery and Mapping Agency (NIMA) of the U.S. Department of Defense. The mission was designed to use a single-pass radar interferometer to produce a digital elevation model (DEM) of the Earth's land surface between about 60 deg north and 56 deg south latitude. When completed, the DEM will have 30 m pixel spacing and about 15 m vertical accuracy. Two orthorectified image mosaics (one from the ascending passes with illumination from the southeast and one from descending passes with illumination from the southwest) will also be produced.

Farr, Tom G.; Kobrick, Mike

2000-01-01

7

RADAR Reveals Titan Topography  

NASA Technical Reports Server (NTRS)

The Cassini Titan RADAR Mapper is a K(sub u)-band (13.78 GHz, lambda = 2.17 cm) linear polarized RADAR instrument capable of operating in synthetic aperture (SAR), scatterometer, altimeter and radiometer modes. During the first targeted flyby of Titan on 26 October, 2004 (referred to as Ta) observations were made in all modes. Evidence for topographic relief based on the Ta altimetry and SAR data are presented here. Additional SAR and altimetry observations are planned for the T3 encounter on 15 February, 2005, but have not been carried out at this writing. Results from the T3 encounter relevant to topography will be included in our presentation. Data obtained in the Ta encounter include a SAR image swath

Kirk, R. L.; Callahan, P.; Seu, R.; Lorenz, R. D.; Paganelli, F.; Lopes, R.; Elachi, C.

2005-01-01

8

Water slope and discharge in the Amazon River estimated using the shuttle radar topography mission digital elevation model  

Microsoft Academic Search

We find that the standard deviation, hence error, of the water surface elevation data from the Shuttle Radar Topography Mission (SRTM) is 5.51 m for basin-wide, regional and local Amazon mainstem reaches. This error implies a minimum reach length of 733km in order to calculate a reliable water-surface slope. Resulting slopes are 1.92 +\\/- 0.19 cm\\/km for Manacapuru, 2.86 +\\/-

Gina LeFavour; Doug Alsdorf

2005-01-01

9

Vegetation height estimation from Shuttle Radar Topography Mission and National Elevation Datasets  

Microsoft Academic Search

A study was conducted to determine the feasibility of obtaining estimates of vegetation canopy height from digital elevation data collected during the 2000 Shuttle Radar Topography Mission (SRTM). The SRTM sensor mapped 80% of the Earth's land mass with a C-band Interferometric Synthetic Aperture Radar (InSAR) instrument, producing the most complete digital surface map of Earth. Due to the relatively

Josef Kellndorfer; Wayne Walker; Leland Pierce; Craig Dobson; Jo Ann Fites; Carolyn Hunsaker; John Vona; Michael Clutter

2004-01-01

10

Radar Measurements of Martian Topography.  

National Technical Information Service (NTIS)

During the 1967 opposition, the planet Mars was observed with the Haystack radar, operated at a frequency of 7840 MHz (3.8-cm wavelength). Sufficient sensitivity was available to measure for the first time, in terms of round-trip echo delay, the variation...

G. H. Pettengill L. P. Rainville C. C. Counselman I. I. Shapiro

1968-01-01

11

Radar interferometry studies of the earth's topography  

NASA Technical Reports Server (NTRS)

Digital elevation models (DEMs) which have been acquired using the TOPSAR interferometric radar sensor are directly applicable to geological and geophysical studies. Attention is presently given to three illustrative examples of the use of DEMs: the correction of remote-sensing observations for local slope and topographic effects, topographic expressions of erosion and uplift in alluvial fans, and volcanology. The greatest advantages of TOPSAR over conventional photogrammetry include rapidity of data collection, high spatial and vertical resolution, and the ability to obtain contiguous data independent of cloud cover.

Evans, Diane L.; Farr, Tom G.; Zebker, Howard A.; Van Zyl, Jakob J.; Mouginis-Mark, Peter J.

1992-01-01

12

Topography estimation with interferometric synthetic aperture radar using fringe detection  

NASA Technical Reports Server (NTRS)

Methods are presented for using Synthetic Aperture Radar (SAR) interferometry data to estimate surface topography. An expression is given to relate the elevation of a ground point to the phase difference of SAR images received from two spatially separated antennas. An iterative algorithm which solves for the position and elevation of each point in the image simultaneously is developed. One of the critical issues that determines the accuracy of the terrain mapping is the phase unwrapping. An approach to the problem by fringe line detection is proposed. The algorithms are tested with two Seasat SAR images of terrain near Yellowstone National Park. The resultant elevation map is compared with a USGS terrain elevation model. The error of the SAR elevation with respect to the digital terrain map is about 8.2 percent of the total terrain variation.

Lin, Qian; Vesecky, John F.; Zebker, Howard A.

1991-01-01

13

Accuracy and resolution of shuttle radar topography mission data  

Microsoft Academic Search

We assess the accuracy and resolution of topography data provided by the Shuttle Radar Topography Mission (SRTM) through spectral comparisons with the National Elevation Dataset (NED) and a high-resolution laser data set of the 1999 Hector Mine earthquake rupture. We find that SRTM and the NED are coherent for wavelengths greater than 200 m, however the spatial resolution of the

Bridget Smith; David Sandwell

2003-01-01

14

Digital LPI Radar Detector.  

National Technical Information Service (NTIS)

The function of a Low Probability of Intercept (LPI) radar is to prevent its interception by an Electronic Support (ES) receiver. This objective is generally achieved through the use of a radar waveform that is mismatched to those waveforms for which an E...

P. G. Ong H. K. Teng

2001-01-01

15

Shuttle Radar Topography Mission: A Global DEM.  

National Technical Information Service (NTIS)

Digital topographic data are critical for a variety of civilian, commercial, and military applications. Scientists use Digital Elevation Models (DEM) to map drainage patterns and ecosystems, and to monitor land surface changes over time. The mountain-buil...

T. G. Farr M. Kobrick

2000-01-01

16

High spatial resolution radar altimetry for global Earth topography mapping  

Microsoft Academic Search

This paper summarises the work performed by Alenia Aerospazio in the design of new radar altimeter systems suitable for high spatial resolution Earth topography observation. The instrument concept proposed is based on the application of synthetic aperture processing and interferometric techniques to a conventional Ku band pulse limited system. The major design features and expected performance are briefly presented

G. Angino; F. Impagnatiello; C. Zelli

1997-01-01

17

Macromolecular Topography Leaps into the Digital Age  

NASA Technical Reports Server (NTRS)

A low-cost, real-time digital topography system is under development which will replace x-ray film and nuclear emulsion plates. The imaging system is based on an inexpensive surveillance camera that offers a 1000x1000 array of 8 im square pixels, anti-blooming circuitry, and very quick read out. Currently, the system directly converts x-rays to an image with no phosphor. The system is small and light and can be easily adapted to work with other crystallographic equipment. Preliminary images have been acquired of cubic insulin at the NSLS x26c beam line. NSLS x26c was configured for unfocused monochromatic radiation. Six reflections were collected with stills spaced from 0.002 to 0.001 degrees apart across the entire oscillation range that the reflections were in diffracting condition. All of the reflections were rotated to the vertical to reduce Lorentz and beam related effects. This particular CCD is designed for short exposure applications (much less than 1 sec) and so has a relatively high dark current leading to noisy raw images. The images are processed to remove background and other system noise with a multi-step approach including the use of wavelets, histogram, and mean window filtering. After processing, animations were constructed with the corresponding reflection profile to show the diffraction of the crystal volume vs. the oscillation angle as well as composite images showing the parts of the crystal with the strongest diffraction for each reflection. The final goal is to correlate features seen in reflection profiles captured with fine phi slicing to those seen in the topography images. With this development macromolecular topography finally comes into the digital age.

Lovelace, J.; Bellamy, H.; Snell, E. H.; Borgstahl, G.

2003-01-01

18

Customizable Digital Receivers for Radar  

NASA Technical Reports Server (NTRS)

Compact, highly customizable digital receivers are being developed for the system described in 'Radar Interferometer for Topographic Mapping of Glaciers and Ice Sheets' (NPO-43962), NASA Tech Briefs, Vol. 31, No. 7 (August 2007), page 72. The receivers are required to operate in unison, sampling radar returns received by the antenna elements in a digital beam-forming (DBF) mode. The design of these receivers could also be adapted to commercial radar systems. At the time of reporting the information for this article, there were no commercially available digital receivers capable of satisfying all of the operational requirements and compact enough to be mounted directly on the antenna elements. A provided figure depicts the overall system of which the digital receivers are parts. Each digital receiver includes an analog-to-digital converter (ADC), a demultiplexer (DMUX), and a field-programmable gate array (FPGA). The ADC effects 10-bit band-pass sampling of input signals having frequencies up to 3.5 GHz. The input samples are demultiplexed at a user-selectable rate of 1:2 or 1:4, then buffered in part of the FPGA that functions as a first-in/first-out (FIFO) memory. Another part of the FPGA serves as a controller for the ADC, DMUX, and FIFO memory and as an interface between (1) the rest of the receiver and (2) a front-panel data port (FPDP) bus, which is an industry-standard parallel data bus that has a high data-rate capability and multichannel configuration suitable for DBF. Still other parts of the FPGA in each receiver perform signal-processing functions. The digital receivers can be configured to operate in a stand-alone mode, or in a multichannel mode as needed for DBF. The customizability of the receiver makes it applicable to a broad range of system architectures. The capability for operation of receivers in either a stand-alone or a DBF mode enables the use of the receivers in an unprecedentedly wide variety of radar systems.

Moller, Delwyn; Heavey, Brandon; Sadowy, Gregory

2008-01-01

19

Satellite remote sensing of landscape freeze/thaw state dynamics for complex Topography and Fire Disturbance Areas Using multi-sensor radar and SRTM digital elevation models  

NASA Technical Reports Server (NTRS)

We characterize differences in radar-derived freeze/thaw state, examining transitions over complex terrain and landscape disturbance regimes. In areas of complex terrain, we explore freezekhaw dynamics related to elevation, slope aspect and varying landcover. In the burned regions, we explore the timing of seasonal freeze/thaw transition as related to the recovering landscape, relative to that of a nearby control site. We apply in situ biophysical measurements, including flux tower measurements to validate and interpret the remotely sensed parameters. A multi-scale analysis is performed relating high-resolution SAR backscatter and moderate resolution scatterometer measurements to assess trade-offs in spatial and temporal resolution in the remotely sensed fields.

Podest, Erika; McDonald, Kyle; Kimball, John; Randerson, James

2003-01-01

20

Drainage basin morphometry: a global snapshot from the shuttle radar topography mission  

NASA Astrophysics Data System (ADS)

A suite of 42 morphometric parameters for each of 26 272 drainage basins larger than 100 km2 from the Hydrosheds Shuttle Radar Topography digital elevation model shows the global distribution of Strahler order for streams and drainage basins. At the scale of 15 arc s spacing (232 to 464 m) the largest basins are order 9. Many common parameters depend both on the size of the basin, and the scale of the digital elevation model used for the computations. These drainage basins display the typical longitudinal stream profiles, but the major basins tend to be generally more concave than the smaller basins.

Guth, P. L.

2011-07-01

21

Fault growth and propagation during incipient continental rifting: Insights from a combined aeromagnetic and Shuttle Radar Topography Mission digital elevation model investigation of the Okavango Rift Zone, northwest Botswana  

NASA Astrophysics Data System (ADS)

Digital Elevation Models (DEM) extracted from the Shuttle Radar Topography Mission (SRTM) data and high-resolution aeromagnetic data are used to characterize the growth and propagation of faults associated with the early stages of continental extension in the Okavango Rift Zone (ORZ), northwest Botswana. Significant differences in the height of fault scarps and the throws across the faults in the basement indicate extended fault histories accompanied by sediment accumulation within the rift graben. Faults in the center of the rift either lack topographic expressions or are interpreted to have become inactive, or have large throws and small scarp heights indicating waning activity. Faults on the outer margins of the rift exhibit either (1) large throws or significant scarp heights and are considered older and active or (2) throws and scarp heights that are in closer agreement and are considered young and active. Fault linkages between major fault systems through a process of "fault piracy" have combined to establish an immature border fault for the ORZ. Thus, in addition to growing in length (by along-axis linkage of segments), the rift is also growing in width (by transferring motion to younger faults along the outer margins while abandoning older faults in the middle). Finally, utilization of preexisting zones of weakness allowed the development of very long faults (>100 km) at a very early stage of continental rifting, explaining the apparent paradox between the fault length versus throw for this young rift. This study clearly demonstrates that the integration of the SRTM DEM and aeromagnetic data provides a 3-D view of the faults and fault systems, providing new insight into fault growth and propagation during the nascent stages of continental rifting.

Kinabo, B. D.; Hogan, J. P.; Atekwana, E. A.; Abdelsalam, M. G.; Modisi, M. P.

2008-06-01

22

Titan : Topography Results from Cassini RADAR  

NASA Astrophysics Data System (ADS)

In addition to mapping with SAR imaging, the Cassini RADAR instrument provides a number of other quantitative datasets that are yielding new insights into Titan and the processes that shape it. New topographic results include the recent altimetry profile across Ontario Lacus, a hydrocarbon lake, showing that it is in a topographic low, very flat and very reflective, consistent with a very smooth liquid surface. Another emerging result is an estimate of the global shape from combined altimetry and SARtopo, indicating that the polar radius is smaller than the equatorial, perhaps a factor in the prevalence of lakes at high latitudes. On the smaller scale, topographic measurements are allowing the quantification of the shape of the few observed craters and their ejecta, and of the relationship between topographic and albedo features and the deflection of dune- forming winds. This invited talk summarizes some of these new results.

Lorenz, R. D.; Cassiniradarteam, T. H. E.

2009-04-01

23

On the detection of underwater bottom topography by imaging radars  

NASA Technical Reports Server (NTRS)

A theoretical model which explains basic properties of radar imaging of underwater bottom topography in tidal channels is presented. The surface roughness modulation is described by weak hydrodynamic interaction theory in the relaxation time approximation. In contrast to previous theories on short wave modulation by long ocean waves, a different approximation is used to describe short wave modulation by tidal flow over underwater bottom topography. The modulation depth is proportional to the relaxation time of the Bragg waves. The large modulation of radar reflectivity observed in SEASAT-SAR imagery of sand banks in the Southern Bight of the North Sea are explained by assuming that the relaxation time of 34 cm Bragg waves is of the order of 30-40 seconds.

Alpers, W.

1984-01-01

24

Digital modules for phased array radar  

Microsoft Academic Search

The architecture for a digital transmit\\/receive module for phased array radars is described. The module is a true digital component: control and data inputs and outputs are sequences of numbers. Direct digital synthesis for frequency generation and a digital receiver provide the core of the digital module, and these two items are discussed separately. A wide range of system performance

A. Garrod

1996-01-01

25

Digital modules for phased array radar  

Microsoft Academic Search

The architecture for a digital transmit\\/receive module for phased array radars is described. The module is a true digital component: control and data inputs and outputs are sequences of numbers. Direct digital synthesis for frequency generation and a digital receiver provide the core of the digital module, and these two items are discussed separately. A wide range of system performance

Adrian Garrod

1995-01-01

26

Topography of Titan from Cassini RADAR Stereo Data  

NASA Astrophysics Data System (ADS)

The RADAR instrument onboard the NASA/ESA Cassini spacecraft uses 2.17 cm microwaves to see through the hazy atmosphere of Saturn's giant satellite Titan, forming a synthetic aperture image strip up to 5000 km long with 300-1400 m resolution during a single flyby. To date, 14 such image strips have been acquired, covering a total of 22% of the surface and revealing a strikingly diverse surface shaped by many of the same processes as Earth. Since late 2006, each new image has overlapped previous coverage, providing a stereoscopic view of 5% of Titan's surface. These image overlaps can be analyzed to provide information about Titan's topography at a resolution of a few km horizontally and one hundred to several hundred meters vertically, yielding more detail than any other available source except radarclinometry (shape from shading). Stereo analysis is made challenging by speckle noise and by the link between viewing geometry and illumination: image pairs with the greatest stereo convergence angle would give the most precise height measurements but differ most in illumination and are hardest to compare. We have therefore applied a combination of both manual feature measurements and automated image matching to produce both spot estimates of local relief and digital topographic models (DTMs) of areas where the image quality is suitable. Work to improve the efficiency and geometric rigor of these methods is ongoing at both USGS and JPL. Results to date reveal relief of 1 to1.5 km between the large hydrocarbon seas of the north polar region and surrounding mountains, and 300 to 600 m in caldera-like features containing smaller lakes. These stereo heights agree closely with collocated "SARTopo" elevation estimates obtained by comparison of the overlap between neighboring beams in a single image (Stiles, et al., this conference). The relief near the lakes and seas provides an indirect constraint on the probable depth of those bodies, and hence of Titan's reserves of liquid hydrocarbons (Mitchell et al., this conference). Topography of the extensive longitudinal dunes at low latitudes, and of the presumptive topographic obstacles that divert the dunes, is more subtle and has been difficult to quantify with stereo.

Kirk, R. L.; Howington-Kraus, E.; Stiles, B. W.; Hensley, S.; Mitchell, K. L.; Cassini RADAR Team

2007-12-01

27

A theory of the imaging mechanism of underwater bottom topography by real and synthetic aperture radar  

Microsoft Academic Search

A simple theoretical model of the imaging mechanism of underwater bottom topography in tidal channels by real and by synthetic aperture radar (SAR) is presented. The imaging is attributed to surface effects induced by current variations over bottom topography. The current modulates the short-scale surface roughness, which in turn gives rise to changes in radar reflectivity. The bottom topography-current interaction

Werner Alpers; Ingo Hennings

1984-01-01

28

New Orleans Topography, Radar Image with Colored Height  

NASA Technical Reports Server (NTRS)

[figure removed for brevity, see original site] Click on the image for the animation

About the animation: This simulated view of the potential effects of storm surge flooding on Lake Pontchartrain and the New Orleans area was generated with data from the Shuttle Radar Topography Mission. Although it is protected by levees and sea walls against storm surges of 18 to 20 feet, much of the city is below sea level, and flooding due to storm surges caused by major hurricanes is a concern. The animation shows regions that, if unprotected, would be inundated with water. The animation depicts flooding in one-meter increments.

About the image: The city of New Orleans, situated on the southern shore of Lake Pontchartrain, is shown in this radar image from the Shuttle Radar Topography Mission (SRTM). In this image bright areas show regions of high radar reflectivity, such as from urban areas, and elevations have been coded in color using height data also from the SRTM mission. Dark green colors indicate low elevations, rising through yellow and tan, to white at the highest elevations.

New Orleans is near the center of this scene, between the lake and the Mississippi River. The line spanning the lake is the Lake Pontchartrain Causeway, the world's longest overwater highway bridge. Major portions of the city of New Orleans are actually below sea level, and although it is protected by levees and sea walls that are designed to protect against storm surges of 18 to 20 feet, flooding during storm surges associated with major hurricanes is a significant concern.

Data used in this image were acquired by the Shuttle Radar Topography Mission aboard the Space Shuttle Endeavour, launched on Feb. 11, 2000. SRTM used the same radar instrument that comprised the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR) that flew twice on the Space Shuttle Endeavour in 1994. SRTM was designed to collect 3-D measurements of the Earth's surface. To collect the 3-D data, engineers added a 60-meter (approximately 200-foot) mast, installed additional C-band and X-band antennas, and improved tracking and navigation devices. The mission is a cooperative project between NASA, the National Geospatial-Intelligence Agency (NGA) of the U.S. Department of Defense and the German and Italian space agencies. It is managed by NASA's Jet Propulsion Laboratory, Pasadena, Calif., for NASA's Science Mission Directorate, Washington, D.C.

Location: 30.2 degrees North latitude, 90.1 degrees East longitude Orientation: North toward the top, Mercator projection Size: 80.3 by 68.0 kilometers (49.9 by 42.3 miles) Image Data: Radar image and colored Shuttle Radar Topography Mission elevation model Date Acquired: February 2000

2005-01-01

29

Global Topography of Titan from Cassini RADAR Data (Invited)  

NASA Astrophysics Data System (ADS)

Cassini RADAR data are used to construct a global, albeit sparsely-sampled, topography map, and to generate a hypsometric profile to compare with other planetary bodies. Titan’s hypsogram is unimodal and strikingly narrow compared with the terrestrial planets. To investigate topographic extremes, a novel variant on the classic hypsogram is introduced, with a logarithmic abscissa to highlight mountainous terrain. In such a plot, the top of the terrestrial hypsogram is quite distinct from those of Mars and Venus due to the ‘glacial buzz-saw’ that clips terrestrial topography above the snowline. In contrast to the positive skew seen in other hypsograms, with a long tail of positive relief due to mountains, there is an indication (weak, given the limited data for Titan so far) that the Titan hypsogram appears slightly negatively skewed, suggesting a significant population of unfilled depressions. Limited data permit only a simplistic comparison of Titan topography with other icy satellites but we find that the standard deviation of terrain height (albeit at different scales) is similar to those of Ganymede and Europa. The topography of terrestrial planets is sampled with the same coverage that we have for Titan to gauge what as-yet-undiscovered topographic surprises may yet be hidden by Titan’s haze.

Lorenz, R. D.; Cassini RADAR Team

2010-12-01

30

The Utilization of Side Looking Airborne Radar (SLAR) in the Analysis of Karst Topography.  

National Technical Information Service (NTIS)

Characteristics of mechanical and synthetic radar systems are reviewed. Signature elements of karst topography such as a vertical drainage pattern, knobs, and sinkholes are identified for Side Looking Airborne Radar (SLAR) imagery. SLAR imagery of the Ken...

C. L. Smith A. P. Tribble

1977-01-01

31

Estimating Titan Surface Topography from Cassini Synthetic Aperture RADAR Data  

NASA Astrophysics Data System (ADS)

One of the more vexing dilemmas for RADAR remote sensing is the necessity to choose between altimetry and SAR imaging of a surface. Coincident surface height estimates are very useful in aiding the analysis of the unique surface features observed in the SAR imagery of Titan. Radar altimetry is optimally obtained from nadir observations, whereas SAR requires off-nadir observation in order to construct an image. Co-located nadir altimetry and SAR only occur when observations taken at different times happen to overlap. Stereo techniques can also be used to estimate topography in SAR images, but they also require multiple overlapping observations. Here we discuss a technique, SARTopo, for obtaining 10 km horizontal resolution and 75 m vertical resolution surface height estimates along each SAR swath. The height estimates comprise 1-3 cuts in each SAR pass that are 10 km wide by thousands of km long and extend along the entire long dimension of the SAR image strips. Because we obtain co-located topography along each SAR pass rather than only in regions with overlapping observations, the new technique extends the area over which we have colocated topography and SAR imagery by a couple orders of magnitude. The method is based upon Amplitude Monopulse Comparison, a technique for resolving RADAR targets developed prior to the advent of SAR. The technique requires: 1) accurate spacecraft pointing, 2) accurate spacecraft ephemeris, 3) precise knowledge of the antenna pattern of the RADAR, and 4) downlinked echo data covering the entire antenna footprint. The fourth requirement is met through synergy with Cassini SAR coverage requirements. Cassini SAR commanding and pointing is designed to utilize as much of the antenna footprint as possible in order to maximize cross-track coverage. We describe the technique and present the results for several SAR passes. We validate the technique through comparison with known features such as mountain ranges and dry lakes, and by comparison with colocated nadir altimetry and SAR stereo. In particular, we examine a strip of nadir altimetry obtained along a 1000 km strip observed by SAR a month earlier. The SARTopo height track is within 5-10 km of the nadir altimetry track for a 200 km long section. In this area, the two independent techniques agree closely. Furthermore the region contains prominent high spatial resolution topography, so it provides an excellent test of the resolution and accuracy of both techniques. SARTopo heights are also co-located and agree well with SAR stereo observations. The research described here was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.

Stiles, B. W.; Hensley, S.; Gim, Y.; Kirk, R. L.; Zebker, H. A.; Janssen, M. A.; Johnson, W. T.; West, R. D.

2007-12-01

32

Architecture for a 1-GHz Digital RADAR  

NASA Technical Reports Server (NTRS)

An architecture for a Direct RF-digitization Type Digital Mode RADAR was developed at GSFC in 2008. Two variations of a basic architecture were developed for use on RADAR imaging missions using aircraft and spacecraft. Both systems can operate with a pulse repetition rate up to 10 MHz with 8 received RF samples per pulse repetition interval, or at up to 19 kHz with 4K received RF samples per pulse repetition interval. The first design describes a computer architecture for a Continuous Mode RADAR transceiver with a real-time signal processing and display architecture. The architecture can operate at a high pulse repetition rate without interruption for an infinite amount of time. The second design describes a smaller and less costly burst mode RADAR that can transceive high pulse repetition rate RF signals without interruption for up to 37 seconds. The burst-mode RADAR was designed to operate on an off-line signal processing paradigm. The temporal distribution of RF samples acquired and reported to the RADAR processor remains uniform and free of distortion in both proposed architectures. The majority of the RADAR's electronics is implemented in digital CMOS (complementary metal oxide semiconductor), and analog circuits are restricted to signal amplification operations and analog to digital conversion. An implementation of the proposed systems will create a 1-GHz, Direct RF-digitization Type, L-Band Digital RADAR--the highest band achievable for Nyquist Rate, Direct RF-digitization Systems that do not implement an electronic IF downsample stage (after the receiver signal amplification stage), using commercially available off-the-shelf integrated circuits.

Mallik, Udayan

2011-01-01

33

Interferometric aligment of the X-SAR antenna system on the space shuttle radar topography mission  

NASA Technical Reports Server (NTRS)

The on-orbit alignment of the antenna beams of both the X-band and C-band radar systems during operations of the shuttle radar topography mission/X-band synthetic aperture radar (SRTM/X-SAR)was a key requirement for achieving best interferometric performance.

Geudtner, D.; Zink, M.; Gierull, C.; Shaffer, S.

2002-01-01

34

High-precision Ice Surface Topography Mapping Using Radar Interferometry  

NASA Astrophysics Data System (ADS)

In May 2009 a new radar technique for mapping ice surface topography was demonstrated in a Greenland campaign as part of the NASA International Polar Year activities. This was achieved with the airborne Glacier and Ice Surface Topography Interferometer (GLISTIN-A): a 35.6 GHz single-pass interferometer. Although the technique of using radar interferometry for mapping terrain has been demonstrated before, this is the first such application at millimeter-wave frequencies. Instrument performance indicates swath widths over the ice between 5-7km, with height precisions ranging from 30cm-3m at a posting of 3m x 3m. However, for this application the electromagnetic wave will penetrate an unknown amount into the snow cover thus producing an effective bias that must be calibrated. To evaluate this, GLISTIN-A flew a coordinated collection with the NASA Wallops Airborne Topographic Mapper (ATM) on a transect from Greenland’s Summit to its West coast. Two field calibration sites were established at Colorado Institute for Research in Environmental Science’s Swiss Camp and the National Science Foundation’s Summit station. Additional collections entailed flying a mosaic over Jakobshavn glacier which was repeated after 6 days to reveal surface dynamics. Through detailed calibration and inter-sensor comparisons we were able to observe penetration biases and compare them with theoretical expectations. We also demonstrated GLISTIN-A’s capability to measure the topography of large glacier systems in a seamless fashion and accurately measuring volume changes with a high level of spatial detail. In particular, repeating the airborne campaigns to observe elevation changes over time will allow very accurate volume change measurements. Not only is this very important for mass balance studies to have a precise mass-loss estimate, but the spatial pattern can reveal ice dynamics effects and surface mass balance effects. In this manner a high resolution, high-precision topographic mapping capability is an ideal complement to the ICESat, ICESat II and Cryosat altimeters. Interpolating between the high-accuracy elevation profiles from altimeters such as the ATM or ICESat II with the high-resolution GLISTIN-A swath will enable detailed ice-surface topography maps and extended spatial coverage. The result is the potential for higher fidelity mass-balance estimates and improved observational coverage. Upgrades are currently underway to improve the performance and portability of GLISTIN-A such that, onboard a long-range aircraft this radar can map Greenland’s significant glaciers in a few days. The upgraded GLISTIN-A will be compatible with GlobalHawk installation making, Antarctica basin and coastal mapping feasible. GLISTIN will make more topographic products available to glaciologists, initially through dedicated airborne campaigns or ultimately, perhaps, as a satellite mission.

Moller, D.; Hensley, S.; Michel, T.; Rignot, E. J.; Simard, M.; Krabill, W. B.; Sonntag, J. G.

2010-12-01

35

Digital Earth Workbench: 3D Topography  

NSDL National Science Digital Library

The Digital Earth Workbench is an interactive application that runs on a SGI Onyx Infinite Reality system and is controlled by an Immersive Workbench, tracked stereo glasses, and a tracked wand. The application allows an unprecedented freedom to roam georeferenced datasets at multiple resolutions and timescales. This animation is one of a series of direct creen captures of the application in operation. The occasional menu appearance denotes direct intervention by the operator to add or delete data or to activate a new control option.

Maher, Steve

1999-11-12

36

STS-99 Shuttle Radar Topography Mission Stability and Control  

NASA Technical Reports Server (NTRS)

The Shuttle Radar Topography Mission (SRTM) flew aboard Space Shuttle Endeavor February 2000 and used interferometry to map 80% of the Earth's landmass. SRTM employed a 200-foot deployable mast structure to extend a second antenna away from the main antenna located in the Shuttle payload bay. Mapping requirements demanded precision pointing and orbital trajectories from the Shuttle on-orbit Flight Control System (PCS). Mast structural dynamics interaction with the FCS impacted stability and performance of the autopilot for attitude maneuvers and pointing during mapping operations. A damper system added to ensure that mast tip motion remained with in the limits of the outboard antenna tracking system while mapping also helped to mitigate structural dynamic interaction with the FCS autopilot. Late changes made to the payload damper system, which actually failed on-orbit, required a redesign and verification of the FCS autopilot filtering schemes necessary to ensure rotational control stability. In-flight measurements using three sensors were used to validate models and gauge the accuracy and robustness of the pre-mission notch filter design.

Hamelin, Jennifer L.; Jackson, Mark C.; Kirchwey, Christopher B.; Pileggi, Roberto A.

2001-01-01

37

(abstract) Large-Scale Topography on Main-Belt Asteroids: Evidence from Arecibo Radar Spectra  

NASA Technical Reports Server (NTRS)

Arecibo lambda 13 cm radar spectra of the main belt asteroids 7 Iris, 9 Metis, 12 Victoria, 216 Kleopatra, and 654 Zelinda exhibit evidence for large-scale topography. These asteroids range in diameter from 113 to 200 km and include members of the S,C, and M classes. Radar.

Mitchell, D. L.; Ostro, S. J.; Rosma, K. D.; Campbell, D. B.; Chandler, J. F.; Shapiro, I. I.; Hudson, R. S.

1994-01-01

38

Interferometric alignment of the X-SAR antenna system on the space shuttle radar topography mission  

Microsoft Academic Search

The on-orbit alignment of the antenna beams of both the X-band and C-band radar systems during operations of the shuttle radar topography mission\\/X-band synthetic aperture radar (SRTM\\/X-SAR) was a key requirement for achieving best interferometric performance. In this paper, we consider the X-SAR antenna beam alignment in azimuth. For a single-pass cross-track SAR interferometer, we establish the relation between yaw

Dirk Geudtner; Manfred Zink; Christoph Gierull; Scott Shaffer

2002-01-01

39

Digital filters for synthetic aperture radar  

NASA Astrophysics Data System (ADS)

An organized approach is discussed for designing a set of optimal digital filters that can accommodate a wide range of synthetic-aperture radar (SAR) geometries. The basic SAR signal processing functions are reviewed since they are the basis for the filter design problems. Special digital filter optimality criteria are described that are tailored to the SAR environment. The results from recent filter design publications related to these critria are summarized and examples are included to demonstrate the effectiveness of this approach to designing filters for SAR processors.

Adams, J. W.; Medlin, G. W.; Bayma, R. W.

40

Global Land Topography and Ocean Bathymetry from Radar Altimetry  

NASA Astrophysics Data System (ADS)

A new Digital Elevation Model was compiled for ENVISAT with a 5*5' grid spacing. This Global Model was achieved by integrating a Bathymetry model built by Walter Smith from NOAA and David Sandwell from Scripps Institution of Oceanography, USA, with the Altimetry Corrected Elevations (ACE) produced by Philippa Berry of De Montfort University, UK. Both models present the advantage of associating satellite global altimetry grid with field data (depth sounding for the bathymetry and local DEM for the elevations). To take full advantage of the resolution of both input datasets, two other DEM were also produced with a respective grid spacing of 2' and 30". To obtain a final model with a full, dense and homogeneous coverage, that includes all the information from the initial models and preserves their accuracy, a merge of the data sets was performed carefully respecting the boundary between land and ocean because both original grids had different resolutions. Then, the entire dataset was divided in small geographical tiles that were separately triangulated and interpolated. Edge effects were avoided by taking in consideration an overlap boundary zone. Finally, three grids were obtained at different resolutions, 30 arcseconds, 2 arcminutes and 5 arcminutes (respectively, 1, 4 and 10 km approximately) to be used for applications requiring different scales. These grids are the first global models including essentially satellite radar altimeter measurements of land elevation and ocean bathymetry merged together, giving a unity and a complete, dense and homogeneous coverage of the world, with an unprecedented accuracy. This new global model at 5-arcminutes resolution will replace the previous model used in ENVISAT data processing and the model at 30-arcsecond resolution will be also used for MERIS and ASAR application projects.

Defrenne, D.; Benveniste, J.

41

Digital evaluation of SEASAT-SAR radar image data  

Microsoft Academic Search

The use of spaceborne digital radar image data for small scale topographic and thematic mapping was studied. The information content of digital L-band radar data were analyzed; various evaluation methods of digital image processing for filtering, edge detection, and statistical analysis were employed and tested with regard to their applicability. The tests reveal which surface types and structures can be

Berthold Pfeiffer

1988-01-01

42

Modeling of fluidized ejecta emplacement over digital topography on Venus  

NASA Astrophysics Data System (ADS)

The FLOW computer model of McEwen and Malin (1989) modified for application to the study of Venus fluidized ejecta blankets (FEBs) demonstrates that relatively low viscosities, yield strengths, and initial velocities are required to duplicate the observed flow paths of the outflow materials. The model calculates the velocities and simulated flow paths of gravity flows over Magellan topography. The model is formulated to determine flow movements from initial conditions, gravitational acceleration, and resistance to motion as described by Coulomb, viscous, and turbulent resistance forces. Successful duplication of observed FEB flow paths has been achieved for the FEB craters Addams, Isabella, and Cochran. When used as a simple energy-line model, the model requires low coefficients of friction to extend FEBs to near their observed termini in the synthetic aperture radar (SAR) imagery, although the resulting straight flow lines do not follow the observed flow paths well. For Bingham flow, the model requires low values of viscosity and yield strength which are more similar to pyroclastic or debris flows than basaltic lavas. Flows of 100-m depth require 1 to 2 orders of magnitude higher values of both viscosity and yield strength than 10-m-deep flows. The complicated nature of the flow lines for the low velocity model suggests that FEBs were probably emplaced under variably laminar and turbulent flow conditions, where underlying topography influenced both the direction and energy of flow materials.

Johnson, Jeffrey R.; Gaddis, Lisa

43

Ocean Topography Experiment (TOPEX) Radar Altimeter. Abstract Only.  

National Technical Information Service (NTIS)

A spaceflight qualified Radar Altimeter capable of achieving the TOPEX Mission measurement precision requirement of 2-centimeters, is provided and its performance (Engineering Assessment) will be evaluated after launch and continuously during its 3-year m...

L. C. Rossi D. W. Hancock G. S. Hayne

1988-01-01

44

Hybrid Optical/Digital Processor for Radar Imaging.  

National Technical Information Service (NTIS)

Essex is developing a prototype hybrid optical/digital processor for radar image formation using wideband arbitrary waveforms. The processor is called the Advanced Optical Processor (AOP) and is a hybrid acousto- optic/digital processor that generates hig...

K. Frampton P. Stover

2003-01-01

45

Fractal mapping of digitized images - Application to the topography of Arizona and comparisons with synthetic images  

Microsoft Academic Search

The concept of fractal mapping is introduced and applied to digitized topography of Arizona. It is shown that the fractal statistics satisfy the topography of the state to a good approximation. The fractal dimensions and roughness amplitudes from subregions are used to construct maps of these quantities. It is found that the fractal dimension of actual two-dimensional topography is not

J. Huang; D. L. Turcotte

1989-01-01

46

Topography Estimation With Interferometric Synthetic Aperture Radar Using Fringe Detection  

Microsoft Academic Search

We present new methods for using SAR interferometry data to estimate surface topography. To begin an expression is given to relate the elevation of a ground point to the phase difference of SAR images received from two spatially separated antennas. An iterative algorithm is developed, which solves for the position and elevation of each point in the image simultaneously. One

Qian Lin; John F. Vesecky; Howard A. Zebker

1991-01-01

47

Weighting in digital synthetic aperture radar processing  

NASA Technical Reports Server (NTRS)

Weighting is employed in synthetic aperture radar (SAR) processing to reduce the sidelobe response at the expense of peak center response height and mainlobe resolution. The weighting effectiveness in digital processing depends not only on the choice of weighting function, but on the fineness of sampling and quantization, on the time bandwidth product, on the quadratic phase error, and on the azimuth antenna pattern. The results of simulations conducted to uncover the effect of these parameters on azimuth weighting effectiveness are presented. In particular, it is shown that multilook capabilities of future SAR systems may obviate the need for consideration of the antenna pattern, and that azimuth time-bandwidth products of over 200 are probably required before the digital results begin to approach the ideal results.

Dicenzo, A.

1979-01-01

48

APQ-102 imaging radar digital image quality study  

NASA Astrophysics Data System (ADS)

A modified APQ-102 sidelooking radar collected synthetic aperture radar (SAR) data which was digitized and recorded on wideband magnetic tape. These tapes were then ground processed into computer compatible tapes (CCT's). The CCT's may then be processed into high resolution radar images by software on the CYBER computer.

Griffin, C. R.; Estes, J. M.

1982-11-01

49

Digital signal processing for target detection in FMCW radar  

Microsoft Academic Search

The paper describes a method of digital signal processing for extracting and isolating targets in the return signal of an FMCW radar. Digital filtering of the frequency spectrum of the return signal is followed by nonlinear optimization to detect the presence of multiple targets amid clutter. Results using a practical radar show that the method gives enhanced detection of weak

A. E. Carr; L. G. Cuthbert; A. D. Olver

1981-01-01

50

Digital signal processing for target detection in FMCW radar  

NASA Astrophysics Data System (ADS)

The paper describes a method of digital signal processing for extracting and isolating targets in the return signal of an FMCW radar. Digital filtering of the frequency spectrum of the return signal is followed by nonlinear optimization to detect the presence of multiple targets amid clutter. Results using a practical radar show that the method gives enhanced detection of weak return signals.

Carr, A. E.; Cuthbert, L. G.; Olver, A. D.

1981-10-01

51

Space Radar Altimetry Development from Ocean Monitoring to Land Topography.  

National Technical Information Service (NTIS)

The evolution of radar altimetry capability from monitoring of the ocean state to global coverage missions though ERS-1 and RA-2 instruments is presented. ERS-1 was launched on 17 Jul. 1991. RA-2 is scheduled for the First European Polar Mission in 1998. ...

G. Levrini F. S. Rubertone R. Somma

1992-01-01

52

Digital Beamforming Synthetic Aperture Radar (DBSAR) Polarimetric Upgrade  

NASA Technical Reports Server (NTRS)

The Digital Beamforming Synthetic Aperture Radar (DBSAR) is a state-of-the-art radar system developed at NASA/Goddard Space Flight Center for the development and implementation of digital beamforming radar techniques. DBSAR was recently upgraded to polarimetric operation in order to enhance its capability as a science instrument. Two polarimetric approaches were carried out which will be demonstrated in upcoming flight campaigns.

Rincon, Rafael F.; Perrine, Martin; McLinden, Matthew; Valett, Susan

2011-01-01

53

Compact Digital Receiver Development for Radar Based Remote Sensing  

Microsoft Academic Search

This paper is the first of a series of publications that discusses the design and implementation of an inexpensive, nearly all-digital FPGA-based radar receiver which can be used in a variety of applications including single\\/dual-polarization weather radar, sidelobe cancellation, a subarray module for a digital beam-forming phased-array radar, and other applications where a compact, low-power, low-cost receiver is needed. The

M. Yearyl; R. Kelleyl; J. Meierl; S. Ongl; R. Palmer

2008-01-01

54

The Information Content of Interferometric Synthetic Aperture Radar: Vegetation and Underlying Surface Topography  

NASA Technical Reports Server (NTRS)

This paper first gives a heuristic description of the sensitivity of Interferometric Synthetic Aperture Radar to vertical vegetation distributions and underlying surface topography. A parameter estimation scenario is then described in which the Interferometric Synthetic Aperture Radar cross-correlation amplitude and phase are the observations from which vegetation and surface topographic parameters are estimated. It is shown that, even in the homogeneous-layer model of the vegetation, the number of parameters needed to describe the vegetation and underlying topography exceeds the number of Interferometric Synthetic Aperture Radar observations for single-baseline, single-frequency, single-incidence-angle, single-polarization Interferometric Synthetic Aperture Radar. Using ancillary ground-truth data to compensate for the underdetermination of the parameters, forest depths are estimated from the INSAR data. A recently-analyzed multibaseline data set is also discussed and the potential for stand-alone Interferometric Synthetic Aperture Radar parameter estimation is assessed. The potential of combining the information content of Interferometric Synthetic Aperture Radar with that of infrared/optical remote sensing data is briefly discussed.

Treuhaft, Robert N.

1996-01-01

55

Analysis of radar images by means of digital terrain models  

NASA Technical Reports Server (NTRS)

It is pointed out that the importance of digital terrain models in the processing, analysis, and interpretation of remote sensing data is increasing. In investigations related to the study of radar images, digital terrain models can have a particular significance, because radar reflection is a function of the terrain characteristics. A procedure for the analysis and interpretation of radar images is discussed. The procedure is based on a utilization of computer simulation which makes it possible to produce simulated radar images on the basis of a digital terrain model. The simulated radar images are used for the geometric and radiometric rectification of real radar images. A description of the employed procedures is provided, and the obtained results are discussed, taking into account a test area in Northern California.

Domik, G.; Leberl, F.; Kobrick, M.

1984-01-01

56

A novel digital x-ray topography system  

NASA Astrophysics Data System (ADS)

X-ray topography (XRT) is recognized as being a powerful tool for directly imaging defects in single crystals, semiconductor wafers and epitaxially grown layers. The timely identification of defects can lead to increased yields and significant cost savings in wafer processing. The primary limitation to its general usage within the semiconductor community has been the difficulty in system use and difficulty in integration into an in-line analytical tool. We have developed a novel, high-speed digital XRT method that can be implemented on a standard high-resolution x-ray diffraction (HRXRD) system equipped with a wafer translation stage and a microfocus tube (or a small aperture in front of a standard point source). It is also appropriate for an in-line fab tool with robot loading and automated operation. In this paper, we discuss the theory and present examples from work undertaken on a variety of materials, including: silicon, compound semiconductors and ionic crystals. Reflection and transmission methods are illustrated. Data were collected on a HRXRD system with a microfocus source and a CCD detector, and an innovative software integration and processing algorithm. Algorithms for full automation of the alignment, exposure and data collection processes have been worked out. It is estimated that the dedicated XRT tool now in prototype form will be capable of scanning a full 300 mm wafer in reflection in under two hours at 50 ?m resolution and one hour at 15 ?m resolution.

Bowen, D. K.; Wormington, M.; Feichtinger, P.

2003-05-01

57

Extraction of Martian valley networks from digital topography  

NASA Technical Reports Server (NTRS)

We have developed a novel method for delineating valley networks on Mars. The valleys are inferred from digital topography by an autonomous computer algorithm as drainage networks, instead of being manually mapped from images. Individual drainage basins are precisely defined and reconstructed to restore flow continuity disrupted by craters. Drainage networks are extracted from their underlying basins using the contributing area threshold method. We demonstrate that such drainage networks coincide with mapped valley networks verifying that valley networks are indeed drainage systems. Our procedure is capable of delineating and analyzing valley networks with unparalleled speed and consistency. We have applied this method to 28 Noachian locations on Mars exhibiting prominent valley networks. All extracted networks have a planar morphology similar to that of terrestrial river networks. They are characterized by a drainage density of approx.0.1/km, low in comparison to the drainage density of terrestrial river networks. Slopes of "streams" in Martian valley networks decrease downstream at a slower rate than slopes of streams in terrestrial river networks. This analysis, based on a sizable data set of valley networks, reveals that although valley networks have some features pointing to their origin by precipitation-fed runoff erosion, their quantitative characteristics suggest that precipitation intensity and/or longevity of past pluvial climate were inadequate to develop mature drainage basins on Mars.

Stepinski, T. F.; Collier, M. L.

2004-01-01

58

Mapping Ocean Surface Topography with a Synthetic-Aperture Interferometry Radar  

NASA Technical Reports Server (NTRS)

We propose to apply the technique of synthetic aperture radar interferometry to the measurement of ocean surface topography at spatial resolution approaching 1 km. The measurement will have wide ranging applications in oceanography, hydrology. and marine geophysics. The oceanographic and related societal applications are briefly discussed in the paper. To meet the requirements for oceanographic applications, the instrument must be flown in an orbit with proper sampling of ocean tides.

Fu, Lee-Lueng; Rodriguez, Ernesto

2006-01-01

59

Minimizing interference in automotive radar using digital beamforming  

NASA Astrophysics Data System (ADS)

Millimetre wave radar is an essential part of automotive safety functions. A high interference tolerance, especially with other radar sensors, is vital. This paper gives an overview of the motivation, the boundary conditions and related activities in the MOSARIM project funded by the European Union and concerned with interference mitigation in automotive radars. Current and planned activities considering Digital Beamforming (DBF) as a method for interference mitigation are presented.

Fischer, C.; Goppelt, M.; Blöcher, H.-L.; Dickmann, J.

2011-07-01

60

Digital signal processing in FMCW radar marine tank gauging system  

Microsoft Academic Search

A marine tank gauging system based on the FMCW radar is introduced. The range measurement principle of this system is presented. The digital signal processing procedure based on the FFT is described. The experimental results are also reported

Qi GuoQing

1996-01-01

61

A digital leakage cancellation scheme for monostatic FMCW radar  

Microsoft Academic Search

A novel heterodyne scheme based on real-time digital signal processing is proposed for leakage cancellation in monostatic frequency modulated continuous wave (FMCW) radars. Compared to conventional analog implementation, the advantages of the proposed scheme include that the DC offset existing in analog mixers affecting the cancellation performance are eliminated. A radar test bed at 26 GHz has been built. The

Kaihui Lin; Razmig Hagop Messerian; Yuanxun Wang

2004-01-01

62

Applying digital VLSI technology to radar signal processing  

Microsoft Academic Search

In spite of great advances in radar signal processing related to technological progress, the present digital signal processing (DSP) capability, still falls well short of what could be specified by a radar designer. It is, therefore, necessary to pay attention to the special characteristics of VLSI circuits in order to be able to exploit silicon as fully as possible as

J. B. G. Roberts; P. Simpson; B. C. Merrifield

1986-01-01

63

Fractal mapping of digitized images - Application to the topography of Arizona and comparisons with synthetic images  

NASA Technical Reports Server (NTRS)

The concept of fractal mapping is introduced and applied to digitized topography of Arizona. It is shown that the fractal statistics satisfy the topography of the state to a good approximation. The fractal dimensions and roughness amplitudes from subregions are used to construct maps of these quantities. It is found that the fractal dimension of actual two-dimensional topography is not affected by the adding unity to the fractal dimension of one-dimensional topographic tracks. In addition, consideration is given to the production of fractal maps from synthetically derived topography.

Huang, J.; Turcotte, D. L.

1989-01-01

64

Geological Interpretations of the Topography of Selected Regions of Venus from Arecibo to Goldstone Radar Interferometry  

NASA Technical Reports Server (NTRS)

Radar interferometry using Arecibo to transmit and three antennas at the Goldstone to receive was conducted on 14 dates in Spring, 2001. This data has been used so far to generate DEMs (digital elevation models) for several of the dates with pixel resolution of 0.5-1.0 km. Additional information is contained in the original extended abstract.

Jurgens, R. F.; Margot, J-L.; Simons, M.; Pritchard, M. E.; Slade, M. A.

2002-01-01

65

Digital processing system of the radar echo-signals  

NASA Astrophysics Data System (ADS)

A PC-based system for the digital processing of radar echo signals is described. The proposed system, involving user-level interactive RSAS, is implemented on a PC-based digital processing system compatible with the IBM-XT. Both hardware and software features are considered.

Giryn, Andrzej

66

Millimetre wave FMCW radar as a tool for 3D Terrain mapping of volcanic topography  

NASA Astrophysics Data System (ADS)

Since the start of eruptive activity in 1995 the lava dome at the Soufrière Hills Volcano, Montserrat has grown and collapsed repeatedly with many of the larger rockfall collapse events producing hazardous pyroclastic flows. Monitoring the timing, direction and magnitude of these avalanches remains a major difficulty due to the fundamental problem of being able to continuously observe the changing topography of the lava dome during periods of low or zero visibility. Cloud cover can last for weeks at a time, during which the location and magnitude of significant changes (tens of metres) to the dome topography can remain undetected. Since 2002 the Millimetre Wave and High Filed ESR group in St Andrews have developed portable ground based FMCW millimetre wave radar for use as a practical field tool for the remote sensing of volcanic terrain at active lava domes. The primary aim of the All-weather Volcano Topography Imaging Sensor (AVTIS) instruments is to record 3D topography at safe ranges of up to 7km to enable round-the-clock monitoring of lava dome bulk growth, i.e. detect topographic changes on the order of meters per day. The original AVTIS prototype developed between 2002 and 2008 proved the viability of low power millimetre wave radar for remote sensing of volcanoes, combining active active and passive measurement modes to record the 3D shape, reflectivity and brightness temperature of target topography in most viewing conditions. There currently exist two instruments: AVTIS2, a long range (7km) portable rover designed for quick and practical field deployment and AVTIS3, a smaller autonomous unit deployed in 2011 under telemetered control at a fixed site at the Soufrière Hills Volcano, Montserrat. We will describe the how the AVTIS instruments are deployed in the field, the quality of the primary ranging and radiometric measurements, and the post processing techniques used to derive the geophysical products of the target terrain, surface temperature, and reflectivity. We will also discuss the estimation of volume change and lava extrusion rate from these data products.eft: AVTIS-2 rover (top) and AVTIS-3 installationat the Soufriere Hills Volcano. Centre: AVTIS-temperature image draped over an AVTIS-DEM of 2005 lava dome. Right: Photo of SHV from Windy Hill obscured by cloud (top) and contemporary AVTIS radar reflectivity image (bottom) in 2011.

Macfarlane, D.; Wadge, G.; Odbert, H. M.; Stinton, A. J.; Roberston, D.; James, M. R.; Pinkerton, H.

2012-12-01

67

Real-Time Digital Signal Processing of Phased Array Radars  

Microsoft Academic Search

With the advance of hardware and software technology, modern phased array radars are now built with commercial-off-the-shelf (COTS) components, and it opens up a new era in real-time resource scheduling of digital signal processing. This paper targets the essential issues in building a component-oriented signal processor (SP), which is one of the two major modules in modern phased array radars.

Chin-fu Kuo; Tei-wei Kuo; Cheng Chang

2003-01-01

68

Digital active-aperture phased-array radar  

Microsoft Academic Search

A digital active-aperture architecture for phased-array radars has been proposed by NRL to improve performance and reduce the life-cycle cost of future USA Navy radars. Considering various approaches, NRL has been procuring and testing various component alternatives and is implementing the design described above in order to demonstrate this technology. The simulations, analysis, and laboratory measurements that have been performed

B. H. Cantrell; J. W. De Graaf; L. M. Leibowitz

2000-01-01

69

Synthetic Aperture Radar Interferometry for Digital Elevation Model of Kuwait Desert - Analysis of Errors  

NASA Astrophysics Data System (ADS)

Using different combinations of 29 Advanced Synthetic Aperture Radar (ASAR) images, 43 Digital Elevations Models (DEM) were generated adopting SAR Interferometry (InSAR) technique. Due to sand movement in desert terrain, there is a poor phase correlation between different SAR images. Therefore, suitable methodology for generating DEMs of Kuwait desert terrain using InSAR technique were worked out. Time series analysis was adopted to derive the best DEM out of 43 DEMs. The problems related to phase de-correlation over desert terrain are discussed. Various errors associated with the DEM generation are discussed which include atmospheric effects, penetration into soil medium, sand movement. The DEM of Shuttle Radar Topography Mission (SRTM) is used as a reference. The noise levels of DEM of SRTM are presented.

Jassar, H. K. Al; Rao, K. S.

2012-07-01

70

The Glacier and Land Ice Surface Topography Interferometer (GLISTIN): A Novel Ka-band Digitally Beamformed Interferometer  

NASA Technical Reports Server (NTRS)

The estimation of the mass balance of ice sheets and glaciers on Earth is a problem of considerable scientific and societal importance. A key measurement to understanding, monitoring and forecasting these changes is ice-surface topography, both for ice-sheet and glacial regions. As such NASA identified 'ice topographic mapping instruments capable of providing precise elevation and detailed imagery data for measurements on glacial scales for detailed monitoring of ice sheet, and glacier changes' as a science priority for the most recent Instrument Incubator Program (IIP) opportunities. Funded under this opportunity is the technological development for a Ka-Band (35GHz) single-pass digitally beamformed interferometric synthetic aperture radar (InSAR). Unique to this concept is the ability to map a significant swath impervious of cloud cover with measurement accuracies comparable to laser altimeters but with variable resolution as appropriate to the differing scales-of-interest over ice-sheets and glaciers.

Moller, Delwyn K.; Heavey, Brandon; Hodges, Richard; Rengarajan, Sembiam; Rignot, Eric; Rogez, Francois; Sadowy, Gregory; Simard, Marc; Zawadzki, Mark

2006-01-01

71

Digital Processing of Meteorological Radar Signals.  

National Technical Information Service (NTIS)

The paper describes a signal processing technique which reduces the variance to an acceptale level for quantitative measurements using the log power output from the radar as the variable. The decrease in variance is a function of the number of samples tak...

D. Sirmans

1972-01-01

72

Digital Signal Processor for Doppler Radar Sensing of Vital Signs.  

National Technical Information Service (NTIS)

A digital signal processor for Doppler radar sensing of vital signs is described. A voltage waveform signal containing respiration and heartbeat signatures is low-pass filtered (0.7 Hz) for the respiration and band-pass filtered (1.0 - 3.0 Hz) for the hea...

B. Lohman O. Boric-Lubecke V. M. Lubecke P. W. Ong M. M. Sondhi

2001-01-01

73

First Results of Digital Topography Applied to Macromolecular Crystals  

NASA Technical Reports Server (NTRS)

An inexpensive digital CCD camera was used to record X-ray topographs directly from large imperfect crystals of cubic insulin. The topographs recorded were not as detailed as those which can be measured with film or emulsion plates but do show great promise. Six reflections were recorded using a set of finely spaced stills encompassing the rocking curve of each reflection. A complete topographic reflection profile could be digitally imaged in minutes. Interesting and complex internal structure was observed by this technique.The CCD chip used in the camera has anti-blooming circuitry and produced good data quality even when pixels became overloaded.

Lovelace, J.; Soares, A. S.; Bellamy, H.; Sweet, R. M.; Snell, E. H.; Borgstahl, G.

2004-01-01

74

Satellites images, digitized topography, and the recognition of the Xela Caldera, Quezaltenango Valley, Guatemala  

Microsoft Academic Search

The authors propose, based on reconnaissance geology studies and interpretation of landforms as depicted by Landsat Thematic Mapper (TM) images combined with digitized topography, that the Quezaltenango basin of Guatemala is part of a caldera. The Quezaltenango basin is an elliptical depression, about 12 by 25 km and about 500 m deep. The proposed Xela Caldera extends beyond the basin

D. Foley; A. McEwen; W. Duffield; G. Heiken

1992-01-01

75

Roundoff noise analysis for digital Doppler processors in radar scatterometers  

NASA Technical Reports Server (NTRS)

The noise due to finite word length effects for digital Doppler processors (DPP) in radar scatterometers, is analyzed. The roundoff noise-to-signal ratio in the measurement of the radar return signal power is derived. Computer simulations which validate the analytical results are presented. The results can be used in tradeoff studies of hardware design such as number of bits required at each processing stage. The results are used in the design of a DPP for the NASA scatterometer planned to be launched in 1990.

Chi, Chong-Yung; Long, D.; Fuk, K. LI

1986-01-01

76

Digital filter design for radar image formation  

NASA Technical Reports Server (NTRS)

Novel weighted-least-squares approaches to the design of digital filters for SAR applications are presented. The filters belong to three different categories according to their combinations of minimax passband, least-squares stopband, minimax stopband, and maximally-flat passband. For real-time applications, it is important to design the sets of digital filter coefficient tables in an offline environment; the appropriate precomputed filter is then selected for each SAR signal-processing function, as a function of both mode and mapping geometry during real-time processing.

Adams, John W.; Nelson, Jeffrey E.; Banh, N. D.; Moncada, John J.; Bayma, Robert W.

1989-01-01

77

The derivation of a sub-canopy digital terrain model of a flooded forest using synthetic aperture radar  

NASA Technical Reports Server (NTRS)

Synthetic aperture radar data from the Shuttle Imaging Radar-B Mission were combined with the tide surface information to create a digital terrain model for a 70-km by 40-km section of the Mouths of the Ganges forests in southern Bangladesh. The dominance of the interaction phenomenon (canopy to surface or surface to canopy reflection) in flooded forests was exploited to create sub-canopy flood boundary maps for two different tide times. The boundary maps were digitally combined in x, y, z space with tide elevation models created from tide gauge data gridding the survey site and used as input to interpolation routines to create a terrain model. The end product represents a significant step in our ability to characterize the topography and hydrology of wetland ecosystems. The model derived here can be used for simulating tidal flow and nutrient transport from the forest to the marine habitat.

Imhoff, Marc Lee; Gesch, Dean B.

1990-01-01

78

Synthetic aperture radar and digital processing: An introduction  

NASA Technical Reports Server (NTRS)

A tutorial on synthetic aperture radar (SAR) is presented with emphasis on digital data collection and processing. Background information on waveform frequency and phase notation, mixing, Q conversion, sampling and cross correlation operations is included for clarity. The fate of a SAR signal from transmission to processed image is traced in detail, using the model of a single bright point target against a dark background. Some of the principal problems connected with SAR processing are also discussed.

Dicenzo, A.

1981-01-01

79

An update on multi-channel digital receiver development for the phased array radar at the National Weather Radar Testbed  

Microsoft Academic Search

This paper describes the beginning states of a new project that will digitize radar signals coming from eight channels on the phased array antenna at the National Weather Radar Testbed (NWRT) in Norman, Oklahoma. At the current time, a single-channel digital receiver is operational to mimic the current capability. The multi-channel digital data will foster a new generation of adaptive\\/fast

M. Yeary; J. Crain; A. Zahrai; R. Palmer; M. Xue; T.-Y. Yu; G. Zhang; Y. Zhang; R. Doviak; Q. Xu; P. Chilson

2009-01-01

80

Smoothing and Differentiation of the Output of a Doppler Radar by a Digital Spectralanalytic Method.  

National Technical Information Service (NTIS)

A digital method for smoothing and differentiating the output of a Doppler radar is presented. The raw output of the radar is transformed into the frequency domain. Then the appropriate filtering and differentiation operations are performed followed by an...

F. P. Devries

1972-01-01

81

60-m delay-stabilized microwave fiber optic link for the STS-99 Shuttle Radar Topography Mission (SRTM)  

NASA Astrophysics Data System (ADS)

The STS-99 Shuttle Radar Topography Mission (SRTM) employed radar interferometry to gather high resolution imagery used to generate the most detailed 3D map of the earth's surface ever produced. Such a map has a broad range of both military and commercial uses. This 11-day mission of the Space Shuttle Endeavour took place from February 11 to 22, 2000, and covered 80% of the earth's surface. The SRTM project gathered 12.3 Terabytes of imaging data, which is equivalent to more than 20,418 compact disks, and approximately equal to the entire contents of the Library of Congress.

Horwitz, Dennis N.

2001-02-01

82

Interference-Detection Module in a Digital Radar Receiver  

NASA Technical Reports Server (NTRS)

A digital receiver in a 1.26-GHz spaceborne radar scatterometer now undergoing development includes a module for detecting radio-frequency interference (RFI) that could contaminate scientific data intended to be acquired by the scatterometer. The role of the RFI-detection module is to identify time intervals during which the received signal is likely to be contaminated by RFI and thereby to enable exclusion, from further scientific data processing, of signal data acquired during those intervals. The underlying concepts of detection of RFI and rejection of RFI-contaminated signal data are also potentially applicable in advanced terrestrial radio receivers, including software-defined radio receivers in general, receivers in cellular telephones and other wireless consumer electronic devices, and receivers in automotive collision-avoidance radar systems.

Fischman, Mark; Berkun, Andrew; Chu, Anhua; Freedman, Adam; Jourdan, Michael; McWatters, Dalia; Paller, Mimi

2009-01-01

83

Validation of Orthorectified Interferometric Radar Imagery and Digital Elevation Models  

NASA Technical Reports Server (NTRS)

This work was performed under NASA's Verification and Validation (V&V) Program as an independent check of data supplied by EarthWatch, Incorporated, through the Earth Science Enterprise Scientific Data Purchase (SDP) Program. This document serves as the basis of reporting results associated with validation of orthorectified interferometric interferometric radar imagery and digital elevation models (DEM). This validation covers all datasets provided under the first campaign (Central America & Virginia Beach) plus three earlier missions (Indonesia, Red River: and Denver) for a total of 13 missions.

Smith Charles M.

2004-01-01

84

Digital Radar-Signal Processors Implemented in FPGAs  

NASA Technical Reports Server (NTRS)

High-performance digital electronic circuits for onboard processing of return signals in an airborne precipitation- measuring radar system have been implemented in commercially available field-programmable gate arrays (FPGAs). Previously, it was standard practice to downlink the radar-return data to a ground station for postprocessing a costly practice that prevents the nearly-real-time use of the data for automated targeting. In principle, the onboard processing could be performed by a system of about 20 personal- computer-type microprocessors; relative to such a system, the present FPGA-based processor is much smaller and consumes much less power. Alternatively, the onboard processing could be performed by an application-specific integrated circuit (ASIC), but in comparison with an ASIC implementation, the present FPGA implementation offers the advantages of (1) greater flexibility for research applications like the present one and (2) lower cost in the small production volumes typical of research applications. The generation and processing of signals in the airborne precipitation measuring radar system in question involves the following especially notable steps: The system utilizes a total of four channels two carrier frequencies and two polarizations at each frequency. The system uses pulse compression: that is, the transmitted pulse is spread out in time and the received echo of the pulse is processed with a matched filter to despread it. The return signal is band-limited and digitally demodulated to a complex baseband signal that, for each pulse, comprises a large number of samples. Each complex pair of samples (denoted a range gate in radar terminology) is associated with a numerical index that corresponds to a specific time offset from the beginning of the radar pulse, so that each such pair represents the energy reflected from a specific range. This energy and the average echo power are computed. The phase of each range bin is compared to the previous echo by complex conjugate multiplication to obtain the mean Doppler shift (and hence the mean and variance of the velocity of precipitation) of the echo at that range.

Berkun, Andrew; Andraka, Ray

2004-01-01

85

Geostatistical Methods For Determination of Roughness, Topography, And Changes of Antarctic Ice Streams From SAR And Radar Altimeter Data  

NASA Technical Reports Server (NTRS)

The central objective of this project has been the development of geostatistical methods fro mapping elevation and ice surface characteristics from satellite radar altimeter (RA) and Syntheitc Aperture Radar (SAR) data. The main results are an Atlas of elevation maps of Antarctica, from GEOSAT RA data and an Atlas from ERS-1 RA data, including a total of about 200 maps with 3 km grid resolution. Maps and digital terrain models are applied to monitor and study changes in Antarctic ice streams and glaciers, including Lambert Glacier/Amery Ice Shelf, Mertz and Ninnis Glaciers, Jutulstraumen Glacier, Fimbul Ice Shelf, Slessor Glacier, Williamson Glacier and others.

Herzfeld, Ute C.

2002-01-01

86

A semi-automatic method for analysis of landscape elements using Shuttle Radar Topography Mission and Landsat ETM+ data  

NASA Astrophysics Data System (ADS)

In this paper, we demonstrate artificial neural networks—self-organizing map (SOM)—as a semi-automatic method for extraction and analysis of landscape elements in the man and biosphere reserve "Eastern Carpathians". The Shuttle Radar Topography Mission (SRTM) collected data to produce generally available digital elevation models (DEM). Together with Landsat Thematic Mapper data, this provides a unique, consistent and nearly worldwide data set. To integrate the DEM with Landsat data, it was re-projected from geographic coordinates to UTM with 28.5 m spatial resolution using cubic convolution interpolation. To provide quantitative morphometric parameters, first-order (slope) and second-order derivatives of the DEM—minimum curvature, maximum curvature and cross-sectional curvature—were calculated by fitting a bivariate quadratic surface with a window size of 9×9 pixels. These surface curvatures are strongly related to landform features and geomorphological processes. Four morphometric parameters and seven Landsat-enhanced thematic mapper (ETM+) bands were used as input for the SOM algorithm. Once the network weights have been randomly initialized, different learning parameter sets, e.g. initial radius, final radius and number of iterations, were investigated. An optimal SOM with 20 classes using 1000 iterations and a final neighborhood radius of 0.05 provided a low average quantization error of 0.3394 and was used for further analysis. The effect of randomization of initial weights for optimal SOM was also studied. Feature space analysis, three-dimensional inspection and auxiliary data facilitated the assignment of semantic meaning to the output classes in terms of landform, based on morphometric analysis, and land use, based on spectral properties. Results were displayed as thematic map of landscape elements according to form, cover and slope. Spectral and morphometric signature analysis with corresponding zoom samples superimposed by contour lines were compared in detail to clarify the role of morphometric parameters to separate landscape elements. The results revealed the efficiency of SOM to integrate SRTM and Landsat data in landscape analysis. Despite the stochastic nature of SOM, the results in this particular study are not sensitive to randomization of initial weight vectors if many iterations are used. This procedure is reproducible for the same application with consistent results.

Ehsani, Amir Houshang; Quiel, Friedrich

2009-02-01

87

Structural Analysis of Central Luzon, Philippines, Using Shuttle Radar Topography Mission DEM  

NASA Astrophysics Data System (ADS)

Central Luzon Island (13-16°N, 120-122°E), which is bounded to the east by Philippine Trench, to the west by Manila Trench, to the north by Digdig-Dingalan Fault (DDF) and to the south by Verde Island Passage Fault (VIPF), is one of the most seismically and volcanologically active regions in the Philippines. Active seismicity and violent earthquakes in the region are evidently related to the activities along the subduction zones and branches of the Philippine Fault system. Volcanic eruptions and periodic swarms of volcanic earthquakes were also observed in three active volcanoes, i.e., Pinatubo, Taal Volcano Island and Banahaw, while young calderas of Taal and Laguna de Bay are demonstrably fault-bounded. We use the Shuttle Radar Topography Mission (SRTM) data with 90 m spatial resolution to conduct regional mapping of the faults and volcanic structures in this region. Of particular interests are the NE-SW set of normal faults within the Macolod Corridor, the right-lateral Marikina Valley Fault System (MVFS), the prevalence of N-S trending structures and the series of NW-SE structures that parallel to sub-parallel the active branches of the Philippine Fault. Using ENVI software package, we processed the SRTM data into shaded relief images and examined the lineament features from different azimuth directions and angles of artificial illumination. The prominent NW-SE structures in this area revealed by SRTM data were formed as sinistral shears that parallel the seismically active DDF and VIPF. The N-S trending structures, including some segments of MVFS and N-S oriented fold axes, were apparently generated by an earlier E-W compression, but recently displayed dextral movement with localized vertical component and pull-apart zones. The overprinting of recent fault kinematics on previously formed structures suggest a dramatic shift of regional stress distribution in Central Luzon. The dextral movement along MVFS and the extensional NE-SW faults within the Macolod Corridor are consistent with the regional deformation due to coupling of DDF and VIPF movements. Similarly, the E-W to ENE-WSW and N-S to NNE-SSW structures probably formed as Riedel and anti-Riedel shears.

Torres, R.; Mouginis-Mark, P.; Garbeil, H.; Bautista, L.; Ramos, E.

2002-12-01

88

OpenTopography  

NASA Astrophysics Data System (ADS)

OpenTopography is a cyberinfrastructure-based facility for online access to high-resolution topography and tools. The project is an outcome of the Geosciences Network (GEON) project, which was a research project funded several years ago in the US to investigate the use of cyberinfrastructure to support research and education in the geosciences. OpenTopography provides online access to large LiDAR point cloud datasets along with services for processing these data. Users are able to generate custom DEMs by invoking DEM services provided by OpenTopography with custom parameter values. Users can track the progress of their jobs, and a private myOpenTopo area retains job information and job outputs. Data available at OpenTopography are provided by a variety of data acquisition groups under joint agreements and memoranda of understanding (MoU). These include national facilities such as the National Center for Airborne Lidar Mapping, as well as local, state, and federal agencies. OpenTopography is also being designed as a hub for high-resolution topography resources. Datasets and services available at other locations can also be registered here, providing a "one-stop shop" for such information. We will describe the OpenTopography system architecture and its current set of features, including the service-oriented architecture, a job-tracking database, and social networking features. We will also describe several design and development activities underway to archive and publish datasets using digital object identifiers (DOIs); create a more flexible and scalable high-performance environment for processing of large datasets; extend support for satellite-based and terrestrial lidar as well as synthetic aperture radar (SAR) data; and create a "pluggable" infrastructure for third-party services. OpenTopography has successfully created a facility for sharing lidar data. In the next phase, we are developing a facility that will also enable equally easy and successful sharing of services related to these data.

Baru, C.; Arrowsmith, R.; Crosby, C.; Nandigam, V.; Phan, M.; Cowart, C.

2012-04-01

89

Digitally tunable physicochemical coding of material composition and topography in continuous microfibres  

NASA Astrophysics Data System (ADS)

Heterotypic functional materials with compositional and topographical properties that vary spatiotemporally on the micro- or nanoscale are common in nature. However, fabricating such complex materials in the laboratory remains challenging. Here we describe a method to continuously create microfibres with tunable morphological, structural and chemical features using a microfluidic system consisting of a digital, programmable flow control that mimics the silk-spinning process of spiders. With this method we fabricated hydrogel microfibres coded with varying chemical composition and topography along the fibre, including gas micro-bubbles as well as nanoporous spindle-knots and joints that enabled directional water collection. We also explored the potential use of the coded microfibres for tissue engineering applications by creating multifunctional microfibres with a spatially controlled co-culture of encapsulated cells.

Kang, Edward; Jeong, Gi Seok; Choi, Yoon Young; Lee, Kwang Ho; Khademhosseini, Ali; Lee, Sang-Hoon

2011-11-01

90

Digital elevation models of the Moon from Earth-based radar interferometry  

Microsoft Academic Search

Three-dimensional (3D) maps of the nearside and polar regions of the Moon can be obtained with an Earth-based radar interferometer. This paper describes the theoretical background, experimental setup, and processing techniques for a sequence of observations performed with the Goldstone Solar System Radar in 1997. These data provide radar imagery and digital elevation models of the polar areas and other

Jean-Luc Margot; Donald B. Campbell; Raymond F. Jurgens; Martin A. Slade

2000-01-01

91

FPGA based IF digital receiver for the PARSAX - Polarimetric agile radar  

Microsoft Academic Search

An FPGA-based digital receiver has been developed to perform real-time processing for the PARSAX radar. It is a fully polarimetric FMCW radar with dual-orthogonal sounding signals, which has the possibility to measure all elements of the radar targets polarization scattering matrix simultaneously, in one sweep. This paper presents the design principles including the range profile interpretation, optimal parameters selection and

Zongbo Wang; Oleg A. Krasnov; Leo P. Ligthart; F. van der Zwan

2010-01-01

92

Digital filtering, calibration and correlation analysis of radar-echoes from the tropo- and stratosphere  

Microsoft Academic Search

VHF-radars have been successfully used for remote sensing of the lower and middle atmosphere. The received radar-echoes are digitized and these raw data are processed in several sequential steps. By digitally filtering the raw data which is equivalent to a compression or a coherent integration, the amount of data is reduced and at the same time the signal-to-noise ratio is

R. Ruester; R. F. Woodman

1978-01-01

93

Digital Data Acquisition for Laser Radar for Vibration Analysis.  

National Technical Information Service (NTIS)

Laser radar for vibration analysis represents a military application to develop a target identification system in the future. The problem addressed is how to analyze the vibrations of a target illuminated by the laser radar to achieve a positive identific...

F. G. Montes

1998-01-01

94

A digital elevation model of the Greenland Ice Sheet derived from combined laser and radar altimetry data  

NASA Astrophysics Data System (ADS)

When estimating elevation changes of ice-covered surfaces from radar altimetry, it is important to correct for slope-induced errors. They cause the reflecting point of the pulse to move up-slope and thus return estimates in the wrong coordinates. Slope-induced errors can be corrected for by introducing a Digital Elevation Model (DEM). In this work, such a DEM is developed for the Greenland Ice Sheet using a combination of Envisat radar and ICESat laser altimetry. If time permits, CryoSat radar altimetry will be included as well. The reference year is 2010 and the spatial resolution 2.5 x 2.5 km. This is in accordance with the results obtained in the ESA Ice Sheets CCI project showing that a 5 x 5 km grid spacing is reasonable for ice sheet-wide change detection (Levinsen et al., 2013). Separate DEMs will be created for the given data sets, and the geostatistical spatial interpolation method collocation will be used to merge them, thus adjusting for potential inter-satellite biases. The final DEM is validated with temporally and spatially agreeing airborne lidar data acquired in the NASA IceBridge and ESA CryoVex campaigns. The motivation for developing a new DEM is based on 1) large surface changes presently being observed, and mainly in margin regions, hence necessitating updated topography maps for accurately deriving and correcting surface elevation changes, and 2) although radar altimetry is subject to surface penetration of the signal into the snowpack, data is acquired continuously in time. This is not the case with e.g. ICESat, where laser altimetry data were obtained in periods of active lasers, i.e. three times a year with a 35-day repeat track. Previous DEMs e.g. have 2007 as the nominal reference year, or they are built merely from ICESat data. These have elevation errors as small as 10 cm, which is lower than for Envisat and CryoSat. The advantage of an updated DEM consisting of combined radar and laser altimetry therefore is the possibility of achieving a high spatial and temporal coverage, as well as the opportunity to continuously map surface changes relative to an updated topography and slopes. References: Levinsen, J. F., Khvorostovsky, K., Ticconi, F., Shepherd, A., Forsberg, R., Sørensen, L. S., Muir, A., Pie, N., Felikson, D., Flament, T., Hurkmans, R., Moholdt, G., Gunter, B., Lindenbergh, R. C., and Kleinherenbrink, M.: ESA's Ice Sheets CCI: validation and inter-comparison of surface elevation changes derived from laser and radar altimetry over Jakobshavn Isbræ, Greenland - Round Robin results, The Cryosphere Discuss., 7, 5433-5460, 2013.

Fredenslund Levinsen, Joanna; Smith, Ben; Sørensen, Louise S.; Forsberg, René

2014-05-01

95

A High Resolution Radar Altimeter to Measure the Topography of Ice Sheets  

NASA Technical Reports Server (NTRS)

This thesis is a reference for the Advanced Application Flight Experiment (AAFE) altimeter. The transmitter and receiver subsections are described and measurements of their current state is provided. During the 1994 NASA Greenland Experiment, the altimeter experienced several hardware malfunctions. The process of returning the radar to its fully operational state is presented in detail and necessary design modifications are explained. An updated radar user's manual is included along with various circuit designs which need to be implemented. The thesis is intended to provide an incoming graduate student with a solid foundation of the fundamentals of AAFE altimeter operation.

Pawul, Rudolf A.

1997-01-01

96

Radar seeker based autonomous navigation update system using topography feature matching techniques  

Microsoft Academic Search

The discussed navigation update system was designed for an unmanned platform with fire and forget capability. It meets the requirement due to fully autonomous operation. The system concept will be characterized by complementary use of the radar seeker for target identification as well as for navigation function. The system works in the navigation mode during preprogrammable phases where the primary

H. D. Lerche; F. Tumbreagel

1992-01-01

97

Surface features on Mars: ground-based albedo and radar compared with Mariner 9 topography  

Microsoft Academic Search

Earth-based albedo maps of Mars were compared with Mariner 9 television data and ground-based radar profiles to investigate the nature of the bright and dark albedo features. Little correlation was found except at the boundaries of classical albedo features, where some topographic control is indicated. Windblown dust models for seasonal and secular albedo variations are supported, but it is not

Herbert Frey

1974-01-01

98

The Dunes of Shangri-La : New Cassini RADAR results on patterns of aeolian features and the influence of topography  

NASA Astrophysics Data System (ADS)

Recent flybys (T43, T44 - and just prior to this meeting, T48) provide SAR imagery of northern Shangri-La, the large dark region just to the WNW of Xanadu. Previous imaging of SE Shangri-La (T13) showed that dunes there take a pronounced southward dip compared with the E-W direction seen elsewhere. The new data show rather different directions for dunes in northern Shangri-La, and confirm a blocking or divergent influence of Xanadu. Application of monopulse radar methods to retrieve elevations from Cassini SAR images ('SARTopo') now allows us to explore the influence of topography on the local dune (and by implication, wind) patterns, and the relationship between elevation and sediment accumulation. The lack of large positive relief at Xanadu makes its influence on the dunes somewhat surprising. We consider the possible mechanisms of Xanadu's effect on the winds, using terrestrial analogs as a guide. We review the global pattern of dune orientations and their implications for atmospheric circulation: this orientation map presents a challenging constraint for modelers. We note preliminary indications that scatterometry of Titan's dunefields yields azimuth-dependent radar cross-sections (as is the case for terrestrial sand seas) and note future plans for dune studies on Titan with multi-angle observations that will provide constraints on dune-scale slopes and duneforms too small to resolve.

Lorenz, R. D.; Radebaugh, J.; Wall, S. D.; Kirk, R.; Le Gall, A.; Janssen, M. A.; Zebker, H.; Paganelli, F.; Wye, L.; Lunine, J.

2008-12-01

99

Comparison of radar-altimetry data over Greenland with surface topography derived from airborne laser altimetry  

NASA Technical Reports Server (NTRS)

During the Summers of 1991, 1992, and 1993, NASA flew a scanning laser altimeter over transects of the Greenland ice sheet. Airplane location was measured precisely using differential Global Positioning System (GPS) surveying techniques. This allowed all altimetry data to be reduced to an estimate of ice surface elevations relative to the Earth ellipsoid. Repeat flights over the same areas indicate data consistency to 10 to 20 cm. Many of the aircraft flights were made along the ERS-1 'radar-altimeter footprint track' for a commissioning phase orbit. Rigorous comparison between the ERS-1 altimeter measurements and those from the laser altimeter will require analysis of individual ERS-1 altimeter waveforms, and since the information needed to do this is not yet available, results from comparison of TOPEX (Topology Ocean Experiment) Poseidon (T/P) radar altimetry data with laser data obtained at the northernmost limit of the T/P orbits are presented.

Thomas, R. H.; Krabill, W.; Manizade, S.; Swift, R.; Brenner, A.

1994-01-01

100

The Signal Digital Processing in the Millimeter Band FMCW Radar  

Microsoft Academic Search

The frequency-modulated continuous wave-radars - (FMCW-radars) are widely applied in the car road safety systems, the aircraft altimeters, the fusion plasma microwave diagnostics and in other ranging systems of different usage. The most optimal choice in terms of the \\

A. V. Varavin; G. P. Ermak; A. S. Vasilev; I. V. Popov

2007-01-01

101

Surface features on Mars: Ground-based albedo and radar compared with Mariner 9 topography  

NASA Technical Reports Server (NTRS)

Earth-based albedo maps of Mars were compared with Mariner 9 television data and ground-based radar profiles to investigate the nature of the bright and dark albedo features. Little correlation was found except at the boundaries of classical albedo features, where some topographic control is indicated. Wind-blown dust models for seasonal and secular albedo variations are supported, but it is not clear whether the fines are derived from bright or dark parent rock. Mars, like the Earth and Moon, has probably generated two distinct types of crustal material.

Frey, H.

1973-01-01

102

Arecibo to Goldstone Radar Interferometric Topography of Selected Regions of Venus  

NASA Technical Reports Server (NTRS)

New high resolution digital elevation models (DEMs) of the equatorial region of Venus will be merged with Magellan imagery in order to investigate the relationship between the emplacement of the plains and the tesserae, and rifting in Phoebe Region. Additional information is contained in the original extended abstract.

Slade, M. A.; Simons, M.; Pritchard, M. E.; Jurgens, R. F.

2001-01-01

103

Digital beamforming developments for the joint NASA\\/Air Force Space Based Radar  

Microsoft Academic Search

The Space Based Radar (SBR) program includes a joint technology demonstration between NASA and the Air Force to design a low-earth orbiting, 2×50 m L-band (1.26 GHz) radar system for Earth science and intelligence-related observations. A key subsystem aboard SBR is the electronically-steerable digital beamformer (DBF) network that interfaces between 32 smaller subantenna panels in the array and the on-board

Mark A. Fischman; Charles Le

2004-01-01

104

A digital beamforming processor for the joint DoD\\/NASA space based radar mission  

Microsoft Academic Search

The space based radar (SBR) program includes a joint technology demonstration between NASA and the Air Force to design a low-earth orbiting, 2×50 m L-band (1.26 GHz) radar system for both Earth science and intelligence-related observations. A key subsystem aboard SBR is the electronically-steerable digital beamformer (DBF) network that interfaces between 32 smaller sub-antenna panels in the array and the

Mark A. Fischman; Charles Le; Paul A. Rosen

2004-01-01

105

GEOS-3 ocean current investigation using radar altimeter profiling. [Gulf Stream surface topography  

NASA Technical Reports Server (NTRS)

Both quasi-stationary and dynamic departures from the marine geoid were successfully detected using altitude measurements from the GEOS-3 radar altimeter. The quasi-stationary departures are observed either as elevation changes in single pass profiles across the Gulf Stream or at the crowding of contour lines at the western and northern areas of topographic maps generated using altimeter data spanning one month or longer. Dynamic features such as current meandering and spawned eddies can be monitored by comparing monthly mean maps. Comparison of altimeter inferred eddies with IR detected thermal rings indicates agreement of the two techniques. Estimates of current velocity are made using derived slope estimates in conjunction with the geostrophic equation.

Leitao, C. D.; Huang, N. E.; Parra, C. G.

1978-01-01

106

Satellites images, digitized topography, and the recognition of the Xela Caldera, Quezaltenango Valley, Guatemala  

SciTech Connect

The authors propose, based on reconnaissance geology studies and interpretation of landforms as depicted by Landsat Thematic Mapper (TM) images combined with digitized topography, that the Quezaltenango basin of Guatemala is part of a caldera. The Quezaltenango basin is an elliptical depression, about 12 by 25 km and about 500 m deep. The proposed Xela Caldera extends beyond the basin more than 10 km to the north. The geomorphological features of the area that are typical of a geologically young large-scale caldera include bounding walls that have steep interior and gentle exterior slopes; broad flat areas at the base of the walls; at least one large block, about 3 by 12 km, that only partly floundered as the caldera collapsed; resurgence of a younger volcanic dome, flow and small-scale caldera complex (last active in 1818); younger volcanoes located along the structural margin of the major caldera (one of which is currently active) lobate features on the caldera margins that may indicate a multiple sequence of eruptions; and an active, high-temperature geothermal system. The valley is coincident with a gravity low. Extensive ash-flow tuff sheets that have no identified source are located north of the caldera, and may be the outflow deposits. The Xela caldera is similar in size to the Atitlan caldera, which lies about 50 km southeast of Quezaltenango. The Xela Caldera, if confirmed by future studies, may contain undiscovered geothermal resources, may present a significant geologic hazard to the more than 400,000 people who occupy the Quezaltenango valley, and may be a new member of the list of magmatic systems that have the capability to change global climate for several years.

Foley, D. (Pacific Lutheran Univ., Tacoma, WA (United States). Dept. of Earth Sciences); McEwen, A.; Duffield, W. (Geological Survey, Flagstaff, AZ (United States)); Heiken, G. (Los Alamos National Lab., NM (United States))

1992-01-01

107

Sea bottom topography imaging with SAR  

NASA Technical Reports Server (NTRS)

It is well known that under favorable meteorological and hydrodynamical conditions the bottom topography of shallow seas can be mapped with airborne or spaceborne imaging radar. This phenomenon was observed for the first time in 1969 by de Loor and co-workers in Q-band Side Looking Airborne Radar (SLAR) imagery of sandwaves in the North Sea. It is now generally accepted that the imaging mechanism consists of three steps: (1) interaction between (tidal) current and bottom topography causes spatial modulations in the surface current velocity; (2) modulations in the surface current velocity give rise to variations in the spectrum of wind-generated waves, as described by the action balance equation; and (3) variations in the wave spectrum show up as intensity modulations in radar imagery. In order to predict radar backscatter modulations caused by sandwaves, an imaging model, covering the three steps, was developed by the Dutch Sea Bottom Topography Group. This model and some model results will be shown. On 16 Aug. 1989 an experiment was performed with the polarimetric P-, L-, and C-band synthetic aperture radar (SAR) of NASA/JPL. One scene was recorded in SAR mode. On 12 Jul. 1991 another three scenes were recorded, of which one was in the ATI-mode (Along-Track Interferometer). These experiments took place in the test area of the Sea Bottom Topography Group, 30 km off the Dutch coast, where the bottom topography is dominated by sand waves. In-situ data were gathered by a ship in the test area and on 'Measuring Platform Noordwijk', 20 km from the center of the test area. The radar images made during the experiment were compared with digitized maps of the bottom. Furthermore, the profiles of radar backscatter modulation were compared with the results of the model. During the workshop some preliminary results of the ATI measurements will be shown.

Vanderkooij, M. W. A.; Wensink, G. J.; Vogelzang, J.

1992-01-01

108

Mapping the mega paleodrainage basin using shuttle radar topography mission in Eastern Sahara and its impact on the new development projects in Southern Egypt  

Microsoft Academic Search

In the current study, the shuttle radar topography mission (SRTM) data, with ?90 m horizontal resolution, were used to delineate\\u000a the paleodrainage system and their mega basin extent in the East Sahara area. One mega-drainage basin has been detected, covering\\u000a an area of 256 000 km2. It is classified into two sub mega basins. The Uweinate sub mega basin, which

Ahmed Mohamed Youssef

2009-01-01

109

A STATUS REPORT ON THE RF AND DIGITAL COMPONENTS OF THE MULTICHANNEL RECEIVER DEVELOPMENT AT THE NATIONAL WEATHER RADAR TESTBED  

Microsoft Academic Search

This paper describes the status of a project that will simultaneously digitize the radar signals coming from eight channels on the phased array antenna at the Na- tional Weather Radar Testbed (NWRT) in Norman, Ok- lahoma. At the current time, a single-channel digital receiver is operational on this S-band radar to mimic the current WSR-88D capability. The multi-channel dig- ital

M. Yeary; J. Crain; A. Zahrai; R. Kelley; J. Meier; Y. Zhang; I. Ivic; C. Curtis; R. Palmer; T.-Y. Yu; G. Zhang; R. Doviak; P. Chilson; M. Xue; Q. Xu

110

Ice thickness, volume and subglacial topography of Urumqi Glacier No. 1, Tianshan mountains, central Asia, by ground penetrating radar survey  

NASA Astrophysics Data System (ADS)

The results of radar survey for three times are presented, aiming to determine ice thickness, volume and subglacial topography of Urumqi Glacier No. 1, Tianshan Mountains, central Asia. Results show that the distribution of ice is more in the center and lesser at both ends of the glacier. The bedrock is quite regular with altitudes decreasing towards the ice front, showing the U-shaped subglacial valley. By comparison, typical ice thinning along the centerline of the East Branch of the glacier was 10-18 m for the period 1981-2006, reaching a maximum of ˜30 m at the terminus. The corresponding ice volume was 10296.2 × 10 4 m 3, 8797.9 × 10 4 m 3 and 8115.0 × 10 4 m 3 in 1981, 2001 and 2006, respectively. It has decreased by 21.2% during the past 25 years, which is the direct result of glacier thinning. In the same period, the ice thickness, area and terminus decreased by 12.2%, 10.3%, and 3.6%, respectively. These changes are responses to the regional climatic warming, which show a dramatic increase of 0.6°C (10 a) -1 during the period 1981-2006.

Wang, Puyu; Li, Zhongqin; Jin, Shuang; Zhou, Ping; Yao, Hongbing; Wang, Wenbin

2014-05-01

111

The Sensitivity of a Volcanic Flow Model to Digital Elevation Models From Diverse Sources: Digitized Map Contours and Airborne Interferometric Radar  

NASA Astrophysics Data System (ADS)

A growing trend in the field of volcanic hazard assessment is the use of computer models of a variety of flows to predict potential areas of devastation. The accuracy of these computer models depends on two factors, the nature and veracity of the flow model itself, and the accuracy of the topographic data set over which it is run. All digital elevation models (DEMs) contain innate errors. The nature of these depends on the accuracy of the original measurements of the terrain, and on the method used to build the DEM. We investigate the effect that these errors have on the performance of a simple volcanic flow model designed to delineate areas at risk from lahar inundation. The volcanic flow model was run over two DEMs of southern Ruapehu volcano derived from (1) digitized 1:50,000 topographic maps, and (2) airborne C-band synthetic aperture radar interferometry obtained using the NASA AIRSAR system. On steep slopes (exceeding 4 degrees), drainage channels are more likely to be incised deeply, and flow paths predicted by the model are generally in agreement for both DEMs despite the differing nature of the source data. Over shallow slopes (approx. 4 degrees and less), where channels are less deep and are more likely to meander, problems were encountered with flow path prediction in both DEMs due to interpolation errors and forestry. The predicted lateral and longitudinal extent of deposit inundation was also sensitive to the type of DEM used, most likely in response to the differing degrees of surface texture preserved in the DEMs. A technique to refine contour-derived DEMs and reduce the error in predicted flow paths was tested to improve the reliability of the modeled flow path predictions. The suitability of forthcoming topographic measurements acquired by a single-pass space-borne instrument, the NASA Shuttle Radar Topography Mission (SRTM) are also tested.

Stevens, N. F.; Manville, V.; Heron, D. W.

2001-12-01

112

Cryovolcanism on Titan: Latest Evidence from Cassini RADAR Imagery and Topography  

NASA Astrophysics Data System (ADS)

Although not the pervasive agent of resurfacing in the Outer Solar System that it was once thought to be, cryovolcanism, the eruption of low-temperature fluids from the interior of icy worlds, appears to be an important phenomenon on several bodies. One of the icy worlds purported to be cryovolcanically active is Titan; its rich atmosphere contains non-primordial isotopic signatures and a methane abundance that cannot be sustained without active outgassing, and the presence of a subsurface ocean at depth provides a source for such materials. The dominant paradigm on Titan for many years has been one of a cryovolcanically resurfaced world with a magmatic chemistry that is principally ammonia-water. Owing to this, and the uniquely (for an icy world) high atmospheric pressure which suppresses explosivity, effusive eruptions with complex rheologies are expected, possibly akin to terrestrial basaltic eruptions, feeding flows and possibly domes. Cassini has observed several features proposed as cryovolcanic in origin on the basis of morphological consistency with expectations. However, an alternative paradigm of an endogenically-dead Titan has emerged recently, arguing for a crustal origin of atmosphere species, and suggesting that alternative exogenic (primarily erosional and fluvial) processes should be considered for most surface features. We present a critical re-assessment of interpretations of cryovolcanic landforms in the context of this new paradigm, on the basis of additional imagery and new topographic data. Some, such as Ganesa Macula and Tortola Facula, are no longer considered potential cryovolcanoes, mostly because the more recently measured topography contradicts the morphological inferences used as a basis for interpretation. However, observations of ˜200 m thick lobate forms in two locations, Hotei and Sotra, strengthen earlier cryovolcanic interpretations.

Mitchell, Karl L.; Kirk, R. L.; Lopes, R. M. C.; Radebaugh, J.; Lorenz, R. D.; Cassini RADAR Team

2010-10-01

113

Quantization noise in digital signal processing by harmonic analysis in a synthetic-aperture radar  

Microsoft Academic Search

The paper derives and analyzes expressions for assessing the effect of quantization noise arising in digital signal processing by harmonic analysis in a synthetic-aperture radar on the output signal for an arbitrary weight function in an FFT processor. The output signal-to-noise ratio is shown to depend on the FFT base size, the digit-representation length in the processing system, and the

N. A. Sazonov

1985-01-01

114

Optimum digital recursive filters for step scan phased array radars  

Microsoft Academic Search

A design method for recursive filters with optimum clutter rejection is presented. The designed filters are suitable for MTI (moving target indication) systems in step scan phased array radars. The designed filters are optimized for a given clutter power spectrum and a finite number of samples without initialization. The performance of the designed filters was studied by considering their clutter

Hussian Al-Ahmad; Gordon B. Lockhart

1991-01-01

115

A digital ASIC for synthesizing false target radar images  

Microsoft Academic Search

Modern, wideband, inverse synthetic aperture radar (ISAR) is capable of generating images of targets, rendering traditional false target decoy methods obsolete. The paper describes an application specific integrated circuit (ASIC) capable of generating false target decoy images for countering imaging ISARs. The application and operation of the ASIC in an electronic attack system is also discussed. The fully programmable chip

Douglas J. Fouts; P. E. Pace; C. Karow; S. R. T. Ekestorm

2002-01-01

116

Geometric rectification of radar imagery using digital elevation models  

NASA Technical Reports Server (NTRS)

Geologic analysis of radar imagery requires accurate spatial rectification to allow rock type discrimination and meaningful exploitation of multisensor data files. A procedure is described which removes distortions produced by most sources including the heretofore elusive problem of terrain induced effects. Rectified imagery is presented which displays geologic features not apparent in the distorted data.

Naraghi, M.; Stromberg, W.; Daily, M.

1983-01-01

117

The use of digital modulation signals in radar system for detection of nonlinear scatterers  

Microsoft Academic Search

This paper deals with initial application of digital modulation techniques in the radar systems utilizing non-linear junction detection (NLJD) principle. Various types of devices, such as handheld detectors for searching of hidden listening devices, have previously been developed and are commercially available. However, these devices transmit single frequency harmonic waveform which in general limits efficiency of energy transmission to nonlinear

Vladimir Polacek; Radomir Pavlik

2011-01-01

118

An advanced digital signal processor for the HRR polarimetric MMW active guidance radar  

Microsoft Academic Search

Polarimetric CFAR detection procedures are first outlined. An advanced digital signal processor used for MMW polarimetric HRR active precision guiding radar is configured that involves a preamplifier and filter, a spectral analyzer and a DSP-based polarimetric detector\\/discriminator to seek and track ground targets in surface clutter. A fuzzy relative optimal state (FROS) of a processor is conceptualized concerning the compromise

Yong Rin; Benchao Sie; Lui Yongtan

1993-01-01

119

An atlas of November 1978 synthetic aperture radar digitized imagery for oil spill studies  

NASA Technical Reports Server (NTRS)

A data set is described which consists of digitized synthetic aperture radar (SAR) imagery plus correlative data and some preliminary analysis results. This data set should be of value to experimenters who are interested in the SAR instrument and its application to the detection and monitoring of oil on water and other distributed targets.

Maurer, H. E.; Oderman, W.; Crosswell, W. F.

1982-01-01

120

The application of digital signal processing techniques to a teleoperator radar system  

NASA Technical Reports Server (NTRS)

A digital signal processing system was studied for the determination of the spectral frequency distribution of echo signals from a teleoperator radar system. The system consisted of a sample and hold circuit, an analog to digital converter, a digital filter, and a Fast Fourier Transform. The system is interfaced to a 16 bit microprocessor. The microprocessor is programmed to control the complete digital signal processing. The digital filtering and Fast Fourier Transform functions are implemented by a S2815 digital filter/utility peripheral chip and a S2814A Fast Fourier Transform chip. The S2815 initially simulates a low-pass Butterworth filter with later expansion to complete filter circuit (bandpass and highpass) synthesizing.

Pujol, A.

1982-01-01

121

Digital image processing techniques applied to the radar detection problem  

Microsoft Academic Search

The author investigates the utility of applying to the radar detection problem several nonlinear filtering structures that have been shown to be useful in image processing. In particular, a CFAR-(constant-false-alarm-rate-)like window processing technique is described. After describing the form of this processing window and pointing out the similarities between it and both conventional CFAR and median filtering windows, the author

C. R. Guarino

1991-01-01

122

Monitoring of Ground Movement and Generation of Digital Elevation Models Using Interferometric Synthetic Aperture Radar (InSAR) Data  

NASA Astrophysics Data System (ADS)

Interferometric synthetic aperture radar (InSAR) has the potential for measuring deformation of the earth's surface with very high accuracy and for the development of digital elevation models. Both capabilities are of high relevance for ground movement assessment. In addition, when archived raw data is available (post 1992), recent historic movement may be quantifiable. InSAR utilizes satellite-based data acquired at two different times along orbits of a similar trajectory to detect changes in the ground surface elevation. This technique can be used to monitor ground movement for rectangular areas as large as 100 kilometers on a side. Knowledge of topography, geology, trends and mechanics of existing ground movement is required for successful interpretation of InSAR data. The detection of ground surface deformation in terrain of high slope relief terrain is difficult. For ground deformation mapping by means of InSAR it is necessary to separate the motion-related and the topographic phase contributions. This is achieved by using a low resolution digital elevation model (DEM) during the processing of InSAR data. The application of InSAR technology to mining areas provides monitoring of not only the active mine areas but also the adjacent regions that has been affected by mining. Thus InSAR technique proves to be an essential ground monitoring methods in future for mining areas. The results from the InSAR analysis are compared with data from a ground-based monitoring system comprised of measured survey prisms for an open pit mine in Canada. InSAR analysis provided the location of the stable site for relocating the crusher which was affected by movement of pit slope. The presentation will show the application of InSAR technology to various mines in USA and Canada. Besides subsidence evaluation, InSAR data is also used to generate digital elevation models (DEM) and digital terrain models (DTM). The DEM and DTM derived from InSAR data for a mine in Canada is compared with the survey and LIDAR data to demonstrate the applicability of InSAR data to model surface topography.

Panda, B. B.

2013-12-01

123

A novel digital receiver concept for ISRO's future remote sensing radars  

NASA Astrophysics Data System (ADS)

Technology development related to digital, antenna and RF subsystems for Microwave Radar Sensors like Synthetic Aperture Radar, Scatterometer, Altimeter and Radiometer is one of the major activities under ISRO's microwave remote sensing programme, since 1980s. These technologies are now being gainfully utilized for building ISRO's operational Earth Observation missions involving microwave sensors like Radar Imaging Satellite, RISAT SAR, Oceansat-2 Scatterometer, Megha-Tropiques, MADRAS and Airborne SAR for Disaster Management, DMSAR. Concurrently, advanced technology developments in these fields are underway to meet the major technological challenges of building ISRO's proposed advanced microwave missions like ultra-high resolution SAR's, Synthetic Aperture Radiometer (SARAD), Milli-meter and sub-millimeter wave sounders and SAR Constellations for Disaster management as well as Interferometric, Polarmetric and polarmetric interferometry applications. Also, these hardware are being designed with core radar electronics concept, in which the same RF and digital hardware sub-units / modules will be utilized to build different microwave radar sensors. One of the major and common requirements for all these active and passive microwave sensors is the moderate to highspeed data acquisition and signal processing system. Traditionally, the Data acquisition units for all these radar sensors are implemented as stand-alone units, following the radar receivers. For ISRO's C-band airborne SAR (ASAR) and RISAT high resolution SAR, we have designed and developed High Speed 8-bit ADC based I/Q Digitisers, operating at 30.814 MHz and 250 MHz sampling rates, respectively. With the increasing demand of wide bandwidth and ultra-high resolution in imaging and non-imaging radar systems, the technology trend worldwide is towards a digital receiver, involving bandpass or IF sampling, thus eliminating the need for RF down converters and analog IQ demodulators. In order to evolve a generic configuration for all the microwave sensors, we have initiated design and development of a generic L-band digital receiver, consisting of receiver elements (LNA, digital attenuator and Bandpass filter) followed by Analog-to-Digital Converter. The digitised data can then be output in parallel or serial format. Additionally, a digital signal processor performing tasks like data compression, convolution or correlation and formatting can also be integrated with this generic digital receiver. The front end of the receiver is wide-band, catering to bandwidths of upto 2 GHz while the digitisation rates are also of the order of 1-2 GHz. It is proposed to standardize the design and use this generic receiver for front end data acquisition of all the future microwave sensors. It will meet the digitisation requirements of 500 MHz to 1 GHz for ultra-high resolution (0.25-0.5 meter) SAR as well as direct sampling of the signal around 1.4GHz for L-band Synthetic Aperture Radiometer. After initial prototyping using discrete receiver elements and ultra-high speed 8-bit ADC, it will be taken up as a custom ASIC or multi-chip module consisting of RF MMIC's and a mixed signal ADC ASIC. These designs will be fabricated using InP, GaAs or SiGe process technologies at competent foundries like GATEC, SCL, Infineon/Germany, X-Fab/Germany and Ommic-Philips/France. This novel digital receiver will offer several advantages like flexibility, stability, reduced RF hardware and miniaturisation. This paper describes the ultra-high speed design requirements, configuration details and target specifications and salient features of this generic L-band digital receiver for ISRO's future spaceborne and airborne radar missions. It also addresses the associated signal integrity, EMI/EMC and thermal issues.

Desai, Nilesh; Vachhani, J. G.; Soin, Sumit; Agrawal, Rinku; Rao, C. V. N.; Gujraty, Virendra; Rana, Surindersingh

2006-12-01

124

Data processing of Martian topographic information obtained from ground-based radar and spectroscopy and from Mariners 6 and 7. Martian topography elevations: Data processing  

NASA Technical Reports Server (NTRS)

Papers are presented which were published as a result of a project involving the preparation of a topographical elevation contour map of Mars from all data sources available through 1969, as well as the observation of Mars by spectroscopic methods in 1971 to provide additional pressure data for topographic information. Topics of the papers include: the analysis of large-scale Martian topography variations - data preparation from earth based radar, earth based CO2 spectroscopy, and Mariners 6 and 7 CO2 spectroscopy; the analysis of water content in observed Martian white clouds; and Martian, lunar, and terrestrial crusts - a three-dimensional exercise in comparative geophysics.

Anderson, K. A.

1974-01-01

125

A survey of analog-to-digital converter technology for radar applications  

NASA Astrophysics Data System (ADS)

The first section of this report discusses sample and hold devices (SHD) which are required prior to the analog to digital converter (ADC) in most radar applications. The SHDs discussed had acquisition times of 10 microsecs or less. plots of SHD droop rate and aperture uncertainty versus acquisition time are presented. The next section contains details on a variety of commercial off the shelf ADCs that have sampling rates greater than 100 KHz. They are compared by resolution, sampling rate, packaging, logic family, size, cost, power requirements, and temperature stability. Finally, brief descriptions of ADCs in development are discussed, and a resolution versus sampling rate comparison of noncommercial ADCs being manufactured by radar houses and their suppliers is presented. The performance envelopes of the commercial and noncommercial ADCs are then overlayed on the estimated 1988 Radar and ELINT resolution and sampling rate requirements.

Jones, B. E.

1982-03-01

126

Simulation of magnetotelluric fields at Stromboli volcano using unstructured grid finite element techniques together with digital topography and bathymetry data  

NASA Astrophysics Data System (ADS)

Marine volcanoes are particularly demanding when it comes to applying electric or electromagnetic methods to investigate their interiors. First, the surrounding highly conductive sea water represents a significant difference in conductivity with respect to the volcanic edifice, second, the volcano's topography has great impact on the electromagnetic response, and, third, the surrounding sea bed topography heavily distorts electromagnetic fields in frequency bands that interfere with a certain spatial wavelength and amplitude of the bathymetry. By neglecting these issues severe misinterpretations are the inevitable consequence. We present different approaches to 3D vector finite element simulation on unstructured grids which are able to compute plain-wave magnetotelluric fields for models including arbitrary surface and sea bed topography. As an example, we consider Stromboli volcano. One major issue is the incorporation of the Stromboli topography using a digital terrain model so that nearly all geometric features affecting the electromagnetic response are considered and an electromagnetic view on Stromboli's interior becomes possible. By carrying out a number of different synthetic experiments it has become obvious that not only the topography of Stromboli island itself is influencing the behavior of the fields but, even stronger, the topography of the surrounding sea bed within a radius of several tens of kilometers. The experiment therefore comprises three steps which gradually approach the complex setting of the target and map the entire volcanic environment with increasing accuracy. The first step outlines the volcano as a resistive geometric frustum surrounded by conductive sea water and underlain by a resistive substratum. This model already gives fundamental answers concerning the principal frequency-dependent current flow pattern within the edifice and the surrounding sea. For this purpose, the MT response was calculated at the earth/sea and the earth/air interface, respectively, for a period of 1000 s along a profile line of 80 km length centered at the top of the frustum. The most delicate features are encountered at the submarine foot of the volcano and when the profile crosses the shore line. The apparent resistivity slowly decreases while approaching the volcano and steeply increases at its foot. It proceeds in a sigmoidal pattern until the profile reaches the shore line. Then the apparent resistivity drops sharply along the on-shore slope and shows a small spike due to the chopped-off tip of the cone. The whole pattern is symmetric with respect to the center of the frustum giving a valuable cross-check for the accuracy of the simulation. In contrast to the apparent resistivity the phase shows a very stable and smooth behavior with values well below 45 degrees in the vicinity of the volcano. The governing physics is comprehensible if so-called static shift effects are considered. Additional MT frequency soundings were conducted at the top of the frustum and at the sea floor 40 km away from the island giving clear indications for the edifice and the conductive sea in the former case and the vanishing energy of the electromagnetic field due to the strong skin effect within the conductive sea water in the latter case. The second step incorporates a digital terrain model only of the volcanic edifice surrounded by a flat sea bed and the third step includes the regional sea bed topography in addition resulting in a significantly increased complexity of the magnetotelluric response. Finally, we raise questions related to spatial data sampling, experimental design and resolution analysis helping to gain optimum information on a volcanic target and to realistically assess the potential and the limits of electromagnetic exploration methods.

Kütter, Sissy; Franke-Börner, Antje; Börner, Ralph-Uwe; Spitzer, Klaus

2010-05-01

127

A digital signal processing system for coherent laser radar  

NASA Technical Reports Server (NTRS)

A data processing system for use with continuous-wave lidar is described in terms of its configuration and performance during the second survey mission of NASA'a Global Backscatter Experiment. The system is designed to estimate a complete lidar spectrum in real time, record the data from two lidars, and monitor variables related to the lidar operating environment. The PC-based system includes a transient capture board, a digital-signal processing (DSP) board, and a low-speed data-acquisition board. Both unprocessed and processed lidar spectrum data are monitored in real time, and the results are compared to those of a previous non-DSP-based system. Because the DSP-based system is digital it is slower than the surface-acoustic-wave signal processor and collects 2500 spectra/s. However, the DSP-based system provides complete data sets at two wavelengths from the continuous-wave lidars.

Hampton, Diana M.; Jones, William D.; Rothermel, Jeffry

1991-01-01

128

A digital system to produce imagery from SAR data. [Synthetic Aperture Radar  

NASA Technical Reports Server (NTRS)

This paper describes a digital processing algorithm and its associated system design for producing images from Synthetic Aperture Radar (SAR) data. The proposed system uses the Fast Fourier Transform (FFT) approach to perform the two-dimensional correlation process. The range migration problem, which is often a major obstacle to efficient processing, can be alleviated by approximating the locus of echoes from a point target by several linear segments. SAR data corresponding to each segment is correlated separately, and the results are coherently summed to produce full-resolution images. This processing approach exhibits greatly improved computation efficiency relative to conventional digital processing methods.

Wu, C.

1976-01-01

129

Real-Time Digital Signal Processing of Component-Oriented Phased Array Radars  

Microsoft Academic Search

With the advance of hardware and software technology, modern phased array radars are now built with commercial off-the-shelf (COTS) components, and it opens up a new era in real-time resource scheduling of digital signal processing. This paper targets the essential issues in building a component-oriented signal processor (SP), which is one of the two major modules in modern phased array

Chin-fu Kuo; Tei-wei Kuo; Cheng Changt

2000-01-01

130

Analysis of a generalized coding\\/decoding method using FIR digital filters for radar waveform design  

Microsoft Academic Search

Previous results dealing with radar systems utilizing complementary coded pulse compression waveforms are extended. The objective is to show how the generation and compression of such codes can be based on a specific single-input\\/multiple-output FIR (finite-impulsive-response) digital filter structure. Driving this filter with a unit pulse yields all members of a complementary code set sequence simultaneously. A decoder is then

Daniel B. Koch

1990-01-01

131

Topography and Landforms of Ecuador  

USGS Publications Warehouse

EXPLANATION The digital elevation model of Ecuador represented in this data set was produced from over 40 individual tiles of elevation data from the Shuttle Radar Topography Mission (SRTM). Each tile was downloaded, converted from its native Height file format (.hgt), and imported into a geographic information system (GIS) for additional processing. Processing of the data included data gap filling, mosaicking, and re-projection of the tiles to form one single seamless digital elevation model. For 11 days in February of 2000, NASA, the National Geospatial-Intelligence Agency (NGA), the German Aerospace Center (DLR), and the Italian Space Agency (ASI) flew X-band and C-band radar interferometry onboard the Space Shuttle Endeavor. The mission covered the Earth between 60?N and 57?S and will provide interferometric digital elevation models (DEMs) of approximately 80% of the Earth's land mass when processing is complete. The radar-pointing angle was approximately 55? at scene center. Ascending and descending orbital passes generated multiple interferometric data scenes for nearly all areas. Up to eight passes of data were merged to form the final processed SRTM DEMs. The effect of merging scenes averages elevation values recorded in coincident scenes and reduces, but does not completely eliminate, the amount of area with layover and terrain shadow effects. The most significant form of data processing for the Ecuador DEM was gap-filling areas where the SRTM data contained a data void. These void areas are a result of radar shadow, layover, standing water, and other effects of terrain, as well as technical radar interferometry phase unwrapping issues. To fill these gaps, topographic contours were digitized from 1:50,000 - scale topographic maps which date from the mid-late 1980's (Souris, 2001). Digital contours were gridded to form elevation models for void areas and subsequently were merged with the SRTM data through GIS and remote sensing image-processing techniques. The data contained in this publication includes a gap filled, countrywide SRTM DEM of Ecuador projected in Universal Transverse Mercator (UTM) Zone 17 North projection, Provisional South American, 1956, Ecuador datum and a non gap filled SRTM DEM of the Galapagos Islands projected in UTM Zone 15 North projection. Both the Ecuador and Galapagos Islands DEMs are available as an ESRI Grid, stored as ArcInfo Export files (.e00), and in Erdas Imagine (IMG) file formats with a 90 meter pixel resolution. Also included in this publication are high and low resolution Adobe Acrobat (PDF) files of topography and landforms maps in Ecuador. The high resolution map should be used for printing and display, while the lower resolution map can be used for quick viewing and reference purposes.

Chirico, Peter G.; Warner, Michael B.

2005-01-01

132

An investigation of the spatial association between snow depth and topography in a Prairie agricultural landscape using digital terrain analysis  

NASA Astrophysics Data System (ADS)

The association of snowcover depth with topography and land cover was examined for a 1.5 km 2 agricultural site in the Canadian Prairies. Topography was quantified by a suite of general geomorphometric variables that were measured directly by the analysis of a raster digital elevation model (DEM) with a 10 m grid cell size. These variables expressed local surface morphology and relative topographic position. The major land covers represented in the study area were wheat stubble and summerfallow. Point observations of snow depth at the site were obtained near the time of peak snow accumulation and during melt. Initial analysis was made of scatterplots and correlations between snow depth and individual topographic variables. These correlations were weak but illustrated that, at the local scale, snow depth patterns cannot be adequately modelled through simple bivariate relationships with topographic variables. The correlations also showed that snow depth is more strongly related to relative topographic position variables than to variables expressing local surface morphology. Subsequent analysis involved a divisive subdivision of the study site into six terrain units defined in terms of several relative topographic position and land cover variables. The units were used to model the spatial patterns of snow depth that occurred during the observed snowcover situations. Although the terrain classification only reduced the total snow depth variance by approximately 30%, it delineated the major patterns of snow depth observed over the study area and elucidated the spatial relationships between snowcover depth and landscape attributes.

Lapena, David R.; Martz, Lawrence W.

1996-10-01

133

Lunar Topography and Basins Mapped Using a Clementine Stereo Digital Elevation Model  

NASA Technical Reports Server (NTRS)

Planet-wide (1 km/pixel and 5 km/pixel) Digital Elevation Models (DEM) of the Moon have been produced using Clementine UVVIS (Ultraviolet-Visible) stereo. Six new basins have been discovered, two suspected basins have been confirmed, and the dimensions of existing basins better defined. Additional information is contained in the original extended abstract.

Cook, A. C.; Spudis, P. D.; Robinson, M. S.; Watters, T. R.

2002-01-01

134

Impact of recent Global Digital Bathymetry and Topography Models on geoid modelling: Results from two case studies in Balearic and Aegean Seas  

NASA Astrophysics Data System (ADS)

With the realization of the Shuttle Radar Topographic Mission (SRTM) and the free distribution of its global elevation dataset with 3 arcsec (90 m) resolution and less than 16 m vertical accuracy, together with the availability of the higher resolution (30 m) and accuracy (10 m) Digital Terrain Models (DTM) from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), these two valuable sources of uniform DEM data represent a revolution in the world of terrain modelling. DEMs are an important source of data for the generation of high resolution geoids since they provide the high-frequency content of the gravity field spectrum and are suitable for the computation of terrain effects to gravity and indirect effects to the geoid, thus allowing the combination of global geopotential models, local gravity anomalies and information about the earth's topography (represented by a given DEM). However, although such models are available for land, there are no readily accessible Digital Bathymetry Models (DBMs) of equivalent quality for the coastal and oceanic regions. Most of the global DBM's (e.g. ETOPO1, SRTM30, and GEBCO global bathymetric grid) are compilations of heterogeneous data with medium resolution and accuracy. This prevents to exploit the potential of the recent high resolution (1 arcmin) marine free-air gravity anomalies datasets derived from satellite altimetry (such as the DNSC08, and the Sandwell & Smith v18.1 (S&Sv18.1) global solutions) in conjunction with such global DBM's. Fortunately, for some regions, recently have become available DBM's of much better accuracy and resolution, such as the DBM of 1 km resolution for many regions of the Mediterranean Sea which is distributed by IFREMER, the French Research Institute for Exploitation of the Sea. The scope of this study is to use this latest regional DBM in combination with the newly available DNSC08 and SSV18.1 global marine free-air gravity anomalies datasets for marine and near shore geoid modelling of archipelagic (island) areas. We have concentrated in two test regions: (a) the Catalano-Balearic Sea (South of Spain in the NW Meditteranean), where adequate marine and land gravity data allow a detailed evaluation of our processing methodologies and their results and, (b) the Aegean Sea where the presence of many islands in varying distances from the mainland Greece and located on the continental shelf and/or divided by steep sea floor topography present some unique challenges for any high resolution geoid modelling efforts. For both test regions, we generated a combined DEM (C-DEM) using the IFREMER and SRTM 30 arcsec bathymetric data for the sea areas and SRTM 3 arcsec data for the surrounding land areas. In this contribution, we discuss various computational aspects relating to the so-called "Direct Topographical Effect" (DTE) and the "Indirect Topographical Effect" (ITE), the two most significant topographical effects that have to be evaluated when a precise geoid is being compiled. In addition, we outline the evaluation and the impact of the results obtained, especially with regard to the differences in the geoid models when different elevation data are used, and point out the main limitations and possibilities for further improvements in the use of the aforementioned satellite and terrestrial data for regional and local geoid mapping in coastal and island regions. Keywords: IFREMER, SRTM, terrain effects, free-air gravity anomalies, geoid modelling,Digital Bathymetry Models.

Delikaraoglou, D.; Mintourakis, I.; Kallianou, F.

2009-04-01

135

Volume displacement measurement via multi-wavelength digital holographic surface topography at the microscopic level  

NASA Astrophysics Data System (ADS)

In this work multiwavelength digital holography, originally applied to calculate the volume displacement of various macroscopic topographic surface features, is now extended to the case of microscopic objects. Accurate measurements of volume displacement for macroscopic surface features has been achieved using long synthetic wavelengths up to several millimeters, generated via tunable IR laser sources. Microscopic volume measurements are performed via digital holographic microscopy using HeNe and Ar+ ion lasers to generate very short synthetic wavelengths. Practical methods of implementation are considered, including wavelength selection error and the geometric effects of both Michelson and Mach-Zehnder recording configurations on phase measurement. Results include comparisons to standard metrology tools, including 1D profilometry and white light interferometry.

Williams, L.; Banerjee, P. P.; Nehmetallah, G.; Praharaj, S.

2014-02-01

136

Digital processing of orbital radar data to enhance geologic structure - Examples from the Canadian Shield  

NASA Technical Reports Server (NTRS)

Various digital enhancement techniques for SAR are compared using SIR-B and Seasat images of the Canadian Shield. The three best methods for enhancing geological structure were found to be: (1) a simple linear contrast stretch; (2) a mean or median low-pass filter to reduce speckle prior to edge enhancement or a K nearest-neighbor average to cosmetically reduce speckle; and (3) a modification of the Moore-Waltz (1983) technique. Three look directions were coregistered and several means of data display were investigated as means of compensating for radar azimuth biasing.

Masuoka, Penny M.; Harris, Jeff; Lowman, Paul D., Jr.; Blodget, Herbert W.

1988-01-01

137

Combined flatland ST radar and digital-barometer network observations of mesoscale processes  

NASA Technical Reports Server (NTRS)

The paper describes a six-station digital-barometer network centered on the Flatland ST radar to support observational studies of gravity waves and other mesoscale features at the Flatland Atmospheric Observatory in central Illinois. The network's current mode of operation is examined, and a preliminary example of an apparent group of waves evident throughout the network as well as throughout the troposphere is presented. Preliminary results demonstrate the capabilities of the current operational system to study wave convection, wave-front, and other coherent mesoscale interactions and processes throughout the troposphere. Unfiltered traces for the pressure and horizontal zonal wind, for days 351 to 353 UT, 1990, are illustrated.

Clark, W. L.; Vanzandt, T. E.; Gage, K. S.; Einaudi, F. E.; Rottman, J. W.; Hollinger, S. E.

1991-01-01

138

A digital implementation of a radar coherent-on-receive system  

NASA Astrophysics Data System (ADS)

A digital coherent-on receive subsystem was designed, built, and tested in order to provide coherent-on receive operation for pulsed radar systems employing incoherent magnetron transmitters. The design used two finite impulse response filters, which extracted the coherent phase from the return signal by performing a matched filter operation between the transmit and receive signals. The phase locking characteristics of this subsystem were evaluated using a magnetron transmitter, and its performance was compared with that of a conventional coherent oscillator (COHO) which was tested in a similar fashion. Results indicate that in a nonchirped environment, the performance of the digital technique is comparable to that obtained with the COHO, while the possibility of it displaying superior performance in a highly chirped scenario exists.

Fernando, M. C.

1989-09-01

139

Gently dipping normal faults identified with Space Shuttle radar topography data in central Sulawesi, Indonesia, and some implications for fault mechanics  

NASA Astrophysics Data System (ADS)

Space-shuttle radar topography data from central Sulawesi, Indonesia, reveal two corrugated, domal landforms, covering hundreds to thousands of square kilometers, that are bounded to the north by an abrupt transition to typical hilly to mountainous topography. These domal landforms are readily interpreted as metamorphic core complexes, an interpretation consistent with a single previous field study, and the abrupt northward transition in topographic style is interpreted as marking the trace of two extensional detachment faults that are active or were recently active. Fault dip, as determined by the slope of exhumed fault footwalls, ranges from 4° to 18°. Application of critical-taper theory to fault dip and hanging-wall surface slope, and to similar data from several other active or recently active core complexes, suggests a theoretical limit of three degrees for detachment-fault dip. This result appears to conflict with the dearth of seismological evidence for slip on faults dipping less than ~ 30°. The convex-upward form of the gently dipping fault footwalls, however, allows for greater fault dip at depths of earthquake initiation and dominant energy release. Thus, there may be no conflict between seismological and mapping studies for this class of faults.

Spencer, Jon E.

2011-08-01

140

Model-Based Estimation of Forest Canopy Height in Red and Austrian Pine Stands Using Shuttle Radar Topography Mission and Ancillary Data: a Proof-of-Concept Study  

SciTech Connect

In this paper, accurate tree stand height retrieval is demonstrated using C-band Shuttle Radar Topography Mission (SRTM) height and ancillary data. The tree height retrieval algorithm is based on modeling uniform tree stands with a single layer of randomly oriented vegetation particles. For such scattering media, the scattering phase center height, as measured by SRTM, is a function of tree height, incidence angle, and the extinction coefficient of the medium. The extinction coefficient for uniform tree stands is calculated as a function of tree height and density using allometric equations and a fractal tree model. The accuracy of the proposed algorithm is demonstrated using SRTM and TOPSAR data for 15 red pine and Austrian pine stands (TOPSAR is an airborne interferometric synthetic aperture radar). The algorithm yields root-mean-square (rms) errors of 2.5-3.6 m, which is a substantial improvement over the 6.8-8.3-m rms errors from the raw SRTM minus National Elevation Dataset Heights.

Brown Jr., C G; Sarabandi, K; Pierce, L E

2007-04-06

141

Radar  

Microsoft Academic Search

Over 1,000,000 km2 of the equatorial surface of Mars west of the Arsia Mons volcano displays no 3.5-cm radar echo to the very low level of the radar system noise for the Very Large Array; the area displaying this unique property has been terms \\

James R. Zimbelman; Kenneth S. Edgett

1994-01-01

142

Ice sheet studies using synthetic aperture radar  

NASA Technical Reports Server (NTRS)

The objective was to demonstrate the utility of synthetic aperture radar in ice sheet studies. The major advantage of SAR imagery over visible imagery is the all-weather capability of radar and the ability to specify look angle. Available digital SAR imagery over ice sheets was collected and examined both qualitatively and quantitatively using corroborative data, such as LANDSAT imagery, to confirm feature identification and interpretations. A simple scattering model will be developed to assess the relative importance of surface topography, composition, and subsurface layering to the intensity of radar backscatter. Recommendations of system parameters will be made for optimal SAR operation over ice sheets.

Bindschadler, R.

1988-01-01

143

A Model for Radar Images and Its Application to Adaptive Digital Filtering of Multiplicative Noise  

Microsoft Academic Search

Standard image processing techniques which are used to enhance noncoherent optically produced images are not applicable to radar images due to the coherent nature of the radar imaging process. A model for the radar imaging process is derived in this paper and a method for smoothing noisy radar images is also presented. The imaging model shows that the radar image

Victor S. Frost; Josephine Abbott Stiles; K. S. Shanmugan; Julian C. Holtzman

1982-01-01

144

Digital signal processing and numerical analysis for radar in geophysical applications  

NASA Astrophysics Data System (ADS)

Numerical solutions for signal processing are described in this work as a contribution to study of echo detection methods for ionospheric sounder design. The ionospheric sounder is a high frequency radar for geophysical applications. The main detection approach has been done by implementing the spread-spectrum techniques using coding methods to improve the radar's range resolution by transmitting low power. Digital signal processing has been performed and the numerical methods were checked. An algorithm was proposed and its computational complexity was calculated.The proposed detection process combines two channels correlations with the local code and calculates threshold (Vt) by statistical evaluation of the background noise to design a detection algorithm. The noisy signals treatment was performed depending on the threshold and echo amplitude. In each case, the detection was improved by using coherent integration. Synthetic signals, close loop and actual echoes, obtained from the Advanced Ionospheric Sounder (AIS-INGV) at Rome Ionospheric Observatory, were used to verify the process.The results showed that, even in highly noisy environments, the echo detection is possible.Given that these are preliminary results, further studies considering data sets corresponding to other geophysical conditions are needed.

Molina, María G.; Cabrera, M. A.; Ezquer, R. G.; Fernandez, P. M.; Zuccheretti, E.

2013-05-01

145

The application of the ADSP-21020 40-bit floating point DSP microprocessor in a digital Doppler radar  

SciTech Connect

A continuous wave doppler radar system has been designed which is portable, easily deployable and can be remotely controlled. The system is immune to ground clutter and is used for wind speed detection and direction determination. Nearly real time digital signal processing is performed by an Analog Devices ADSP-21020, a 40-bit floating point Digital Signal Processing (DSP) microprocessor. This paper provides an overview of the design of the system including the radio frequency (RF) to digital interface. The various DSP detection algorithms are discussed and compared to system performance and sensitivity. Finally, DSP performance is compared to the performance of an earlier system using Analog Device's ADSP-2100. 6 refs.

Robinson, S.H.; Morrison, R.E.

1991-08-26

146

Analog radar signal design and digital signal processing a Heisenberg nilpotent Lie group approach  

NASA Astrophysics Data System (ADS)

Introductory discussion of radar principles Analog radar signal design The radar synthesis problem The radar invariant problem The compact Heisenberg nilmanifold A geometric approach to cardinal spline interpolation Finite phase space, and finite Fourier transform The phase discontinuity of Fourier optics Conclusions References

Schempp, Walter

147

Landscape-scale extent, height, biomass, and carbon estimation of Mozambique's mangrove forests with Landsat ETM+ and Shuttle Radar Topography Mission elevation data  

NASA Astrophysics Data System (ADS)

Mangroves are salt tolerant plants that grow within the intertidal zone along tropical and subtropical coasts. They are important barriers for mitigating coastal disturbances, provide habitat for over 1300 animal species and are one of the most productive ecosystems. Mozambique's mangroves extend along 2700 km and cover one of the largest areas in Africa. The purpose of this study was to determine the countrywide mean tree height spatial distribution and biomass of Mozambique's mangrove forests using Landsat ETM+ and Shuttle Radar Topography Mission (SRTM) data. The SRTM data were calibrated using the Landsat derived land-cover map and height calibration equations. Stand-specific canopy height-biomass allometric equations developed from field measurements and published height-biomass equations were used to calculate aboveground biomass of the mangrove forests on a landscape scale. The results showed that mangrove forests covered a total of 2909 km2 in Mozambique, a 27% smaller area than previously estimated. The SRTM calibration indicated that average tree heights changed with geographical settings. Even though the coast of Mozambique spans across 16 degrees latitude, we did not find a relationship between latitude and biomass. These results confirm that geological setting has a greater influence than latitude alone on mangrove production. The total mangrove dry aboveground biomass in Mozambique was 23.6 million tons and the total carbon was 11.8 million tons.

Fatoyinbo, Temilola E.; Simard, Marc; Washington-Allen, Robert A.; Shugart, Herman H.

2008-06-01

148

Digital processing considerations for extraction of ocean wave image spectra from raw synthetic aperture radar data  

NASA Technical Reports Server (NTRS)

The digital processing requirements of several algorithms for extracting the spectrum of a detected synthetic aperture radar (SAR) image from the raw SAR data are described and compared. The most efficient algorithms for image spectrum extraction from raw SAR data appear to be those containing an intermediate image formation step. It is shown that a recently developed compact formulation of the image spectrum in terms of the raw data is computationally inefficient when evaluated directly, in comparison with the classical method where matched-filter image formation is an intermediate result. It is also shown that a proposed indirect procedure for digitally implementing the same compact formulation is somewhat more efficient than the classical matched-filtering approach. However, this indirect procedure includes the image formation process as part of the total algorithm. Indeed, the computational savings afforded by the indirect implementation are identical to those obtained in SAR image formation processing when the matched-filtering algorithm is replaced by the well-known 'dechirp-Fourier transform' technique. Furthermore, corrections to account for slant-to-ground range conversion, spherical earth, etc., are often best implemented in the image domain, making intermediate image formation a valuable processing feature.

Lahaie, I. J.; Dias, A. R.; Darling, G. D.

1984-01-01

149

High resolution bed topography beneath the trunk and tributaries of Pine Island Glacier from ice-penetrating radar  

NASA Astrophysics Data System (ADS)

Pine Island Glacier (PIG)in West Antarctica is currently losing ice at a rate equivalent to ~7% of current sea-level rise, and predicting its future is therefore an important scientific goal. Though the glacier has now been the focus of several modelling studies, the different models disagree on the likely future pace of loss and its spread inland. Significantly, all models depend critically on the form of the subglacial conditions used, and though the general form of the bed has been mapped from surveys over the last decade, the resolution of bed required for modelling to be improved, i.e. at the sub-km scale, has hitherto been unavailable. Addressing this dearth of detailed bed information was therefore a key objective for the 2013/14 UK iSTAR (Ice-Sheet Stability and Response) traverse across PIG. We deployed the British Antarctic Survey's DEep-LOoking Radio Echo Sounder (DELORES) to sound 10 x 15 km patches of the bed in six locations across PIG. Each patch was surveyed in 22 parallel transects lying 500 m apart and which were each 15 km long.Along each radar transect, the bed was sounded approximately every 5 m. The patches sample the main trunk of the ice stream, the beds of four of the main tributaries, and as a control site, an inter-tributary ridge. We show that the nature of the bed varies significantly between sites.

Bingham, Rob; Cornford, Stephen; Davies, Damon; De Rydt, Jan; King, Edward; Smith, Andrew; Spagnolo, Matteo; Vaughan, David

2014-05-01

150

Frequency diversity wideband digital receiver and signal processor for solid-state dual-polarimetric weather radars  

NASA Astrophysics Data System (ADS)

The recent spate in the use of solid-state transmitters for weather radar systems has unexceptionably revolutionized the research in meteorology. The solid-state transmitters allow transmission of low peak powers without losing the radar range resolution by allowing the use of pulse compression waveforms. In this research, a novel frequency-diversity wideband waveform is proposed and realized to extenuate the low sensitivity of solid-state radars and mitigate the blind range problem tied with the longer pulse compression waveforms. The latest developments in the computing landscape have permitted the design of wideband digital receivers which can process this novel waveform on Field Programmable Gate Array (FPGA) chips. In terms of signal processing, wideband systems are generally characterized by the fact that the bandwidth of the signal of interest is comparable to the sampled bandwidth; that is, a band of frequencies must be selected and filtered out from a comparable spectral window in which the signal might occur. The development of such a wideband digital receiver opens a window for exciting research opportunities for improved estimation of precipitation measurements for higher frequency systems such as X, Ku and Ka bands, satellite-borne radars and other solid-state ground-based radars. This research describes various unique challenges associated with the design of a multi-channel wideband receiver. The receiver consists of twelve channels which simultaneously downconvert and filter the digitized intermediate-frequency (IF) signal for radar data processing. The product processing for the multi-channel digital receiver mandates a software and network architecture which provides for generating and archiving a single meteorological product profile culled from multi-pulse profiles at an increased data date. The multi-channel digital receiver also continuously samples the transmit pulse for calibration of radar receiver gain and transmit power. The multi-channel digital receiver has been successfully deployed as a key component in the recently developed National Aeronautical and Space Administration (NASA) Global Precipitation Measurement (GPM) Dual-Frequency Dual-Polarization Doppler Radar (D3R). The D3R is the principal ground validation instrument for the precipitation measurements of the Dual Precipitation Radar (DPR) onboard the GPM Core Observatory satellite scheduled for launch in 2014. The D3R system employs two broadly separated frequencies at Ku- and Ka-bands that together make measurements for precipitation types which need higher sensitivity such as light rain, drizzle and snow. This research describes unique design space to configure the digital receiver for D3R at several processing levels. At length, this research presents analysis and results obtained by employing the multi-carrier waveforms for D3R during the 2012 GPM Cold-Season Precipitation Experiment (GCPEx) campaign in Canada.

Mishra, Kumar Vijay

151

Hardware description ADSP-21020 40-bit floating point DSP as designed in a remotely controlled digital CW Doppler radar  

SciTech Connect

A continuous wave Doppler radar system has been designed which is portable, easily deployed, and remotely controlled. The heart of this system is a DSP/control board using Analog Devices ADSP-21020 40-bit floating point digital signal processor (DSP) microprocessor. Two 18-bit audio A/D converters provide digital input to the DSP/controller board for near real time target detection. Program memory for the DSP is dual ported with an Intel 87C51 microcontroller allowing DSP code to be up-loaded or down-loaded from a central controlling computer. The 87C51 provides overall system control for the remote radar and includes a time-of-day/day-of-year real time clock, system identification (ID) switches, and input/output (I/O) expansion by an Intel 82C55 I/O expander. 5 refs., 8 figs., 2 tabs.

Morrison, R.E.; Robinson, S.H.

1991-01-01

152

An 8-bit 2.5 gigasample A\\/D converter multichip module for all-digital radar receiver for AN\\/APS 145 radar on Navy E2-C Airborne Early Warning Aircraft  

Microsoft Academic Search

This paper will discuss multichip module (MCM) technology as it is applied to a prototype high performance direct digitizing channelized radar receiver system under development for the Navy's E2-C Airborne Early Warning Aircraft, which encompasses both analog signals at UHF frequencies and multi-gigahertz digital signals. Critical issues which arise in the design of such a system will be discussed, including

Rick L. Thompson; Michael J. Degerstrom; Wayne L. Walters; Mark E. Vickberg; Paul J. Riemer; Eric L. H. Amundsen; Barry K. Gilbert

1997-01-01

153

Noise Radar for range\\/Doppler processing and digital beamforming using low-bit ADC  

Microsoft Academic Search

Pulse compression radar is used in a great number of radar applications. Excellent range resolution and high resistance to electronic countermeasures (ECM) can be achieved by long wideband modulated pulses, which spread out the transmitted energy in frequency and time. By using random noise as the waveform, the range ambiguity can be suppressed as well. In this paper, noise radar

Sune R. J. Axelsson

2003-01-01

154

Simulation of SAR Images and Radar Coding of Georeferenced Information for Temperate Glacier Monitoring  

Microsoft Academic Search

Synthetic Aperture Radar (SAR) interferometry has the po- tential to measure temperate glacier displacement with a very high precision compared to terrestrial sparse ground measure- ments. But the strong topography of mountainous areas where most alpin glaciers are located makes the use of SAR images rather di-cult. Digital Terrain Model (DTM) are necessary to remove topographic fringes from interferograms and

Andreea JULEA; Gabriel VASILE; Ivan PETILLOT; Michel GAY; Jean-Marie NICOLAS; Philippe BOLON

155

Analysis of large-scale Martian topography variations. I - Data preparation from earth-based radar, earth-based CO2 spectroscopy, and Mariners 6 and 7 CO2 spectroscopy.  

NASA Technical Reports Server (NTRS)

Using direct radar ranging of surface heights on Mars and spectrophotometric observations of absorptions produced by carbon dioxide molecules in the Martian atmosphere, data have been obtained on Martian topographical variations at spatial resolutions ranging from about 100 to 1000 km. These data have been studied and analyzed. As a result, a surface height contour map has been produced which clearly reveals a structural complex of blocks and basins whose distribution enhances the magnitude of low-degree surface harmonics. It is emphasized that Mars possesses unexpectedly pronounced topography which can have important geophysical consequences.

Wells, R. A.

1972-01-01

156

High-resolution Precipitation and Lightning Monitoring by the Ku-band Broadband Radar and the VHF Broadband Digital Interferometer  

NASA Astrophysics Data System (ADS)

We propose a high-resolution precipitation and lightning monitoring for meteorological application. This monitoring is mainly utilized the Ku-band broadband radar (BBR) and the VHF broadband digital interferometer (DITF). The BBR can accurately measure the radar reflectivity factor and the mean Doppler velocity with 5 m resolution over a range from 40 m to several kilometers for 10 W power using a pulse compression technique. The two or more DITFs make us visualize lightning channel propagations in three dimensions. Moreover, we add new functions that integrate these observation data and disclose integration analyses results with the quasi real-time information disclosure system. Initial observations for severe storms with lightning during summer and winter thunderstorm season by these monitoring instruments indicate that we obtain detailed precipitation distribution and detect active convective cells with lightning discharges.

Nakamura, Yoshitaka; Yoshikawa, Eiichi; Akita, Manabu; Morimoto, Takeshi; Ushio, Tomoo; Kawasaki, Zen-Ichiro; Saito, Toshiya; Nishida, Takashi; Sakazume, Norio

157

Experimental investigations of digital signal processing techniques in an FMCW radar for naval application  

Microsoft Academic Search

Recently we have observed increased interest in frequency modulated continuous wave (FMCW) radars, mainly because of their low probability of intercept (LPI) properties. In such radars the information on range of targets appears in the frequency domain and it is obtained on the basis of spectrum analysis carried out for a so called beat signal. The beat signal is a

A. Grzywacz

2002-01-01

158

A digital beamforming processor for the joint DoD/NASA space based radar mission  

NASA Technical Reports Server (NTRS)

The Space Based Radar (SBR) program includes a joint technology demonstration between NASA and the Air Force to design a low-earth orbiting, 2x50 m L-band radar system for both Earth science and intelligence related observations.

Fischman, Mark A.; Le, Charles; Rosen, Paul A.

2004-01-01

159

An improved composite surface model for the radar backscattering cross section of the ocean surface 2. Model response to surface roughness variations and the radar imaging of underwater bottom topography  

Microsoft Academic Search

In the companion paper we have presented an improved composite surface model for the calculation of normalized radar backscattering cross sections (NRCS) of the ocean surface. The proposed model accounts for the impact of the full two-dimensional ocean wave spectrum on the radar backscatter and was shown to reproduce measured absolute NRCS values for a variety of radar configurations and

Roland Romeiser; Werner Alpers

1997-01-01

160

In-flight detection of errors for enhanced aircraft flight safety and vertical accuracy improvement using digital terrain elevation data with an inertial navigation system, global positioning system and radar altimeter  

Microsoft Academic Search

This dissertation discusses integration architectures using digital terrain elevation data (DTED) with an inertial navigation system (INS), a global positioning system (GPS) and a radar altimeter. Two integration architectures are considered: DTED with INS, GPS and radar altimeter for aircraft vertical accuracy improvement during the final approach; and DTED with kinematic GPS (KGPS) and a radar altimeter for enhanced aircraft

Robert Anthony Gray

1999-01-01

161

A Four-Channel 94GHz SiGe-Based Digital Beamforming FMCW Radar  

Microsoft Academic Search

This paper presents a multi-channel frequency-modulated continuous-wave (FMCW) radar sensor operating in the frequency range from 91 to 97 GHz. The millimeter-wave radar sensor utilizes an SiGe chipset comprising a single signal-generation chip and multiple monostatic transceiver (TRX) chips, which are based on a 200-GHz $f_{\\\\rm T}$ HBT technology. The front end is built on an RF soft substrate in

Martin Jahn; Reinhard Feger; Christoph Wagner; Ziqiang Tong; Andreas Stelzer

2012-01-01

162

Comparison of antenna dispersion and digital signal processing effects in ultrawideband Ground Penetrating Radar systems  

NASA Astrophysics Data System (ADS)

In Ground Penetrating Radar it is of great interest to have a pulse width as narrow as possible to achieve best resolution capability. However, ultrawideband antennas may cause distortion to the radar signal due to dispersion, which is dependent on the frequency and bandwidth, as well as the direction of radiation. As dispersion causes an increase of the peak's width, the resolution capability is degraded.

Seyfried, Daniel; Brueckner, Sebastian; Schoebel, Joerg

2014-02-01

163

Radar sounder performances for ESA JUICE mission  

NASA Astrophysics Data System (ADS)

The Jupiter Icy moons Explorer (JUICE) is the first Large-class mission chosen as part of ESA's Cosmic Vision 2015-2025 program. The mission will study Jovian icy moons Ganymede and Europa as potential habitats for life, addressing two key themes of Cosmic Vision namely the conditions for planet formation and the emergence of life, and the Solar System interactions. The radar sounder instrument on this mission will have great potential to address specific science questions such as the presence of subsurface liquid water and ice shell geophysical structures. One major constraint for radar sounding is the roughness of the planetary surface. The work presented will focus on the characterization of Ganymede's surface topography to better understand its surface properties from a radar point of view. These results should help to put constraints on the design of JUICE's radar sounder. We use topographic data derived from the Voyager and Galileo missions images to try to characterize the surface structure and to quantify its geometry (in terms of slopes and RMS heights mainly). This study will help us evaluating the radar budget in a statistical approach. In addition, deterministic simulations of surface radar echoes conducted on synthetic surfaces -extrapolated from Digital Elevation Models- will be presented to better assess radar sounding performances.

Berquin, Y. P.; Kofman, W. W.; Heggy, E.; Hérique, A.

2012-12-01

164

Magellan: Radar performance and data products  

USGS Publications Warehouse

The Magellan Venus orbiter carries only one scientific instrument: a 12.6-centimeter-wavelength radar system shared among three data-taking modes. The syntheticaperture mode images radar echoes from the Venus surface at a resolution of between 120 and 300 meters, depending on spacecraft altitude. In the altimetric mode, relative height measurement accuracies may approach 5 meters, depending on the terrain's roughness, although orbital uncertainties place a floor of about 50 meters on the absolute uncertainty. In areas of extremely rough topography, accuracy is limited by the inherent line-of-sight radar resolution of about 88 meters. The maximum elevation observed to date, corresponding to a planetary radius of 6062 kilometers, lies within Maxwell Mons. When used as a thermal emission radiometer, the system can determine surface emissivities to an absolute accuracy of about 0.02. Mosaicked and archival digital data products will be released in compact disk (CDROM) format.

Pettengill, G. H.; Ford, P. G.; Johnson, W. T. K.; Raney, R. K.; Soderblom, L. A.

1991-01-01

165

Shallow-source aeromagnetic anomalies observed over the West Antarctic Ice Sheet compared with coincident bed topography from radar ice sounding - New evidence for glacial "removal" of subglacially erupted late Cenozoic rift-related volcanic edifices  

USGS Publications Warehouse

Aeromagnetic and radar ice sounding results from the 1991-1997 Central West Antarctica (CWA) aerogeophysical survey over part of the West Antarctic Ice Sheet (WAIS) and subglacial area of the volcanically active West Antarctic rift system have enabled detailed examination of specific anomaly sources. These anomalies, previously interpreted as caused by late Cenozoic subglacial volcanic centers, are compared to newly available glacial bed-elevation data from the radar ice sounding compilation of the entire area of the aeromagnetic survey to test this hypothesis in detail. We examined about 1000 shallow-source magnetic anomalies for bedrock topographic expression. Using very conservative criteria, we found over 400 specific anomalies which correlate with bed topography directly beneath each anomaly. We interpret these anomalies as indicative of the relative abundance of volcanic anomalies having shallow magnetic sources. Of course, deeper source magnetic anomalies are present, but these have longer wavelengths, lower gradients and mostly lower amplitudes from those caused by the highly magnetic late Cenozoic volcanic centers. The great bulk of these >400 (40-1200-nT) anomaly sources at the base of the ice have low bed relief (60-600 m, with about 80%10 million years ago. Eighteen of the anomalies examined, about half concentrated in the area of the WAIS divide, have high-topographic expression (as great as 400 m above sea level) and high bed relief (up to 1500 m). All of these high-topography anomaly sources at the base of the ice would isostatically rebound to elevations above sea level were the ice removed. We interpret these 18 anomaly sources as evidence of subaerial eruption of volcanoes whose topography was protected from erosion by competent volcanic flows similar to prominent volcanic peaks that are exposed above the surface of the WAIS. Further, we infer these volcanoes as possibly erupted at a time when the WAIS was absent. In contrast, at the other extreme, there are a number of shallow-source, volcanic appearing magnetic anomalies overlying the very smooth bed topography in the survey area beneath Ice Stream D (Bindshadler Ice Stream); the glacial bed probably comprises a very thin layer of unconsolidated sediments (till). Probably, the volcanic edifices here were removed at a more rapid rate because of fast glacial flow. A few of the very shallow-source "volcanic" anomalies overlie the ice shelf just downstream of the grounding line of Ice Stream D, suggesting a causal relationship, if the volcanism is recent. ?? 2004 Elsevier B.V. All rights reserved.

Behrendt, J. C.; Blankenship, D. D.; Morse, D. L.; Bell, R. E.

2004-01-01

166

A digital signal processor for Doppler radar sensing of vital signs  

Microsoft Academic Search

A signal processor for the determination of respiration and heart rates in Doppler radar measurements is described. The processor can reliably calculate both rates for a subject at distances as large as 2 m. The rate determination is based on autocorrelation and uses several enhancement techniques, including a center clipper. Several representative results are included to show the future potential

B. Lohman; O. Boric-Lubecke; V. M. Lubecke; P. W. Ong; M. M. Sondhi

2002-01-01

167

Method for crater detection from digital topography data: interpolation based improvement and application to Lunar SELENE LALT data  

NASA Astrophysics Data System (ADS)

Crater detection algorithms (CDAs) are an important subject of recent scientific research, as evident from the numerous recent publications in the field [ASR, 42 (1), 6-19]. In our previous work: (1) all the craters from the major currently available manually assembled catalogues have been merged into the catalogue with 57633 known Martian impact-craters [PSS, 56 (15), 1992-2008]; and (2) the CDA (developed to search for still uncatalogued impact-craters using 1/128° MOLA data) has been used to extend GT-57633 catalogue with 57592 additional craters resulting in GT-115225 catalog [GRS, 48 (5), in press, doi:10.1109/TGRS.2009.2037750]. On the other hand, the most complete catalog for Moon is the Morphological catalog of Lunar craters [edited by V. V. Shevchenko], which includes information on 14923 craters larger than 10km, visible on the lunar nearside and farside. This was the main motivation for application of our CDA to newly available Lunar SELENE LALT data. However, one of the main differences between MOLA and LALT data is the highest available resolution, wherein MOLA is available in 1/128° and LALT in 1/16° . The consequence is that only the largest craters can be detected using LALT dataset. However, this is still an excellent opportunity for further work on CDA in order to prepare it for forthcoming LRO LOLA data (which is expected to be in even better resolution than MOLA). The importance is in the fact that morphologically Martian and Lunar craters are not the same. Therefore, it is important to use the dataset for Moon in order to work on the CDA which is meant for detection of Lunar craters as well. In order to overcome the problem of currently available topography data in low resolution only, we particularly concentrated our work on the CDA's capability to detect very small craters relative to available dataset (up to the extreme case wherein the radius is as small as only two pixels). For this purpose, we improved the previous CDA with a new algorithm for sub-pixel interpolation of elevation samples, before subsequent computations. For elevation samples on larger distances from the crater's center, linear interpolation was used in order to speed-up the computations. For samples closer to the crater's center, the elevation value at the crater's center and relative sub-pixel distance to the selected elevation sample is additionally taken into account. The purpose is to compute the most realistic values for estimated elevation at a selected point. The results are, according to the initial visual evaluation, that numerous craters were successfully detected using SELENE LALT data.

Salamuni?car, Goran; Lon?ari?, Sven

168

The Surface Water and Ocean Topography Mission (SWOT): the Ka-band Radar Interferometer (KaRIn) for water level measurements at all scales  

Microsoft Academic Search

The Surface Water and Ocean Topography (SWOT) mission will study ocean mesoscale and submesoscale phenomena and provide an inventory of storage change and discharge for fresh water bodies and rivers. In this paper, we examine the combination of measurements that will be used by SWOT to achieve a globally consistent data set. We introduce a new channel in the SWOT

Ernesto Rodriguez; Daniel Esteban-Fernandez

2010-01-01

169

Ka-band Digitally Beamformed Airborne Radar Using SweepSAR Technique  

NASA Technical Reports Server (NTRS)

A paper describes a frequency-scaled SweepSAR demonstration that operates at Ka-Band (35.6 GHz), and closely approximates the DESDynl mission antenna geometry, scaled by 28. The concept relies on the SweepSAR measurement technique. An array of digital receivers captures waveforms from a multiplicity of elements. These are combined using digital beamforming in elevation and SAR processing to produce imagery. Ka-band (35.6 GHz) airborne SweepSAR using array-fed reflector and digital beamforming features eight simultaneous receive beams generated by a 40-cm offset-fed reflector and eight-element active array feed, and eight digital receiver channels with all raw data recorded and later used for beamforming. Illumination of the swath is accomplished using a slotted-waveguide antenna radiating 250 W peak power. This experiment has been used to demonstrate digital beamforming SweepSAR systems.

Sadowy, Gregory A.; Chuang, Chung-Lun; Ghaemi, Hirad; Heavey, Brandon A.; Lin, Lung-Sheng S.; Quaddus, Momin

2012-01-01

170

Applications of satellite imagery and digital topography to the construction of a crustal-scale transect across the central Andes at 20[degrees]S latitude  

SciTech Connect

The central Andean plateau is one of the Earth's most remote and poorly mapped regions. The plateau has an average elevation of 3.7 km, and extends from central Peru to at least 30[degrees]S latitude. The plateau and flanking Subandean foldthrust belt (FTB) reach their greatest width near 20[degrees]S, and at this latitude both the FTB and the basin within the plateau (Altiplano basin) are areas of active hydrocarbon exploration. We have used Landsat TM imagery, stereoscopic SPOT imagery, and digital topography to construct a crustal-scale transect across the central Andes in order to better understand Andean tectonics at this latitude. Beginning at the Peru-Chile trench and continuing to the east, the transect crosses the Coastal Cordillera, Longitudinal Valley, Active Magmatic Arc, Altiplano basin, Eastern Cordillera, Subandean fold-thrust belt, and Subandean foreland basin. A digital elevation model across the entire region illustrates that the magmatic arc, Altiplano basin, and Eastern cordillera all lie within the plateau region. Satellite imagery across the transect illustrates the characteristic geology, structure, and geomorphology of each of the major morphotectonic regions, as well as the nature of their boundaries. The transect has led us to a number of new insights on Andean tectonics at this latitude. Most importantly, it supports a two-stage model of Andean Cenozoic growth in which a widespread Oligocene to mid-Miocene compressional deformation in the Altiplano and Eastern Cordillera is followed in the late Miocene and Pliocene by thrusting localized east of the Eastern Cordillera, forming the Subandean fold-thrust belt.

Gubbels, T.L.; Isacks, B.L. (Cornell Univ., Ithaca, NY (United States)); Ellis, J.M. (Chevron Overseas Petroleum Inc., San Ramon, CA (United States))

1993-02-01

171

Capturing Micro-topography of an Arctic Tundra Landscape through Digital Elevation Models (DEMs) Acquired from Various Remote Sensing Platforms  

NASA Astrophysics Data System (ADS)

The need to improve the spatial and temporal scaling and extrapolation of plot level measurements of ecosystem structure and function to the landscape level has been identified as a persistent research challenge in the arctic terrestrial sciences. Although there has been a range of advances in remote sensing capabilities on satellite, fixed wing, helicopter and unmanned aerial vehicle platforms over the past decade, these present costly, logistically challenging (especially in the Arctic), technically demanding solutions for applications in an arctic environment. Here, we present a relatively low cost alternative to these platforms that uses kite aerial photography (KAP). Specifically, we demonstrate how digital elevation models (DEMs) were derived from this system for a coastal arctic landscape near Barrow, Alaska. DEMs of this area acquired from other remote sensing platforms such as Terrestrial Laser Scanning (TLS), Airborne Laser Scanning, and satellite imagery were also used in this study to determine accuracy and validity of results. DEMs interpolated using the KAP system were comparable to DEMs derived from the other platforms. For remotely sensing acre to kilometer square areas of interest, KAP has proven to be a low cost solution from which derived products that interface ground and satellite platforms can be developed by users with access to low-tech solutions and a limited knowledge of remote sensing.

Vargas, S. A., Jr.; Tweedie, C. E.; Oberbauer, S. F.

2013-12-01

172

Soviet oceanographic synthetic aperture radar (SAR) research  

SciTech Connect

Radar non-acoustic anti-submarine warfare (NAASW) became the subject of considerable scientific investigation and controversy in the West subsequent to the discovery by the Seasat satellite in 1978 that manifestations of underwater topography, thought to be hidden from the radar, were visible in synthetic aperture radar (SAR) images of the ocean. In addition, the Seasat radar produced images of ship wakes where the observed angle between the wake arms was much smaller than expected from classical Kelvin wake theory. These observations cast doubt on the radar oceanography community's ability to adequately explain these phenomena, and by extension on the ability of existing hydrodynamic and radar scattering models to accurately predict the observability of submarine-induced signatures. If one is of the opinion that radar NAASW is indeed a potentially significant tool in detecting submerged operational submarines, then the Soviet capability, as evidenced throughout this report, will be somewhat daunting. It will be shown that the Soviets have extremely fine capabilities in both theoretical and experimental hydrodynamics, that Soviet researchers have been conducting at-sea radar remote sensing experiments on a scale comparable to those of the United States for several years longer than we have, and that they have both an airborne and spaceborne SAR capability. The only discipline that the Soviet Union appears to be lacking is in the area of digital radar signal processing. If one is of the opinion that radar NAASW can have at most a minimal impact on the detection of submerged submarines, then the Soviet effort is of little consequence and poses not threat. 280 refs., 31 figs., 12 tabs.

Held, D.N.; Gasparovic, R.F.; Mansfield, A.W.; Melville, W.K.; Mollo-Christensen, E.L.; Zebker, H.A.

1991-01-01

173

Using X-band weather radar measurements to monitor the integrity of digital elevation models for synthetic vision systems  

NASA Astrophysics Data System (ADS)

Synthetic Vision Systems (SVS) provide pilots with displays of stored geo-spatial data representing terrain, obstacles, and cultural features. As comprehensive validation is impractical, these databases typically have no quantifiable level of integrity. Futher, updates to the databases may not be provided as changes occur. These issues limit the certification level and constrain the operational context of SVS for civil aviation. Previous work demonstrated the feasibility of using a real-time monitor to bound the integrity of Digital Elevation Models (DEMs) by using radar altimeter measurements during flight. This paper describes an extension of this concept to include X-band Weather Radar (WxR) measurements. This enables the monitor to detect additional classes of DEM errors and to reduce the exposure time associated with integrity threats. Feature extraction techniques are used along with a statistical assessment of similarity measures between the sensed and stored features that are detected. Recent flight-testing in the area around Juneau, Alaska Airport (JNU) has resulted in a comprehensive set of sensor data that is being used to assess the feasibility of the proposed monitor technology. Initial results of this assessment are presented.

Young, Steven D.; Uijt de Haag, Maarten; Sayre, Jonathon

2003-09-01

174

Dependence of image grey values on topography in SIR-B images  

NASA Technical Reports Server (NTRS)

This paper focuses on the use of a high resolution digital elevation model (DEM) to aid in rectifying and enhancing synthetic aperture radar images. Using a synthetic backscatter image, the SIR-B images are manually rectified and resampled to remove geometric distortions caused by topography. In a second step, an improved reflectance function of incidence angle is derived from the DEM and the rectified image and this function is used to reduce radiometric effects of topography yielding an albedo image which clearly shows the thematic, as opposed to topographic content of the image. The procedure is tested on four SIR-B images of a scene in Argentina (crossover point) that is imaged under different azimuth and incidence angles. The similarity of the resulting images indicates that the procedure effectively reduces artefacts from the images that are dependent on topography.

Domik, G.; Leberl, F.; Cimino, J.

1988-01-01

175

Complementary Code and Digital Filtering for Detection of Weak VHF Radar Signals from the Mesosphere  

Microsoft Academic Search

Measurements of the structure and the dynamics of the middle atmosphere with a fine height resolution have been carried out using the SOUSY-VHF-Radar (SOUSY = SOUnding SYstem), operated by the Max-Planck-Institute for Aeronomy in the Harz mountains in Germany. Since the echoes from the middle atmosphere are coherent within a time scale of the order of a second, the received

Gerhard Schmidt; Rudiger Ruster; Peter Czechowsky

1979-01-01

176

WITTEX: An Innovative Multi-Satellite Radar Altimeter Constellation A Summary Statement for the High-resolution Ocean Topography Science Working Group  

Microsoft Academic Search

WITTEX consists of multiple radar altimeters on individual satellites in the same orbit plane. Earth rotation separates their respective measurement tracks on the surface. In the monostatic version (co-located transmitter and receiver), each satellite generates one track, at nadir, as is standard in pulse-limited ocean altimetry. The nadir altimeters would have two frequencies (to mitigate ionospheric path delays) and a

R. Keith Raney; David L. Porter

177

Comparison of Satellite Radar Altimeter Derived Heights with Global Digital Terrain Model Heights.  

National Technical Information Service (NTIS)

A study of the use of SEASAT and Geosat altimeter data for global height determination is reported. Currently available Global Digital Elevation Models (GDEMs) are of limited spatial resolution and accuracy, while satellite altimetry offers the prospects ...

J. K. Ridley P. A. M. Berry C. M. Birkett C. G. Rapley

1992-01-01

178

Comparing Digital Flood Insurance Rate Maps (DFIRMs) to Interferometric Synthetic Aperture Radar (IFSAR) Products.  

National Technical Information Service (NTIS)

As part of the Federal Emergency Management Agency (FEMA) Map Modernization program, Flood Insurance Rate Maps (FIRMs) are converted from hard copy products to Digital Flood Insurance Rate Maps (DFIRMs). The next generation of DFIRMs will have more data a...

J. J. Damron

2000-01-01

179

Global Topography and Tectonic Plates  

NSDL National Science Digital Library

The goal of this activity is to investigate global topographic and tectonic features, especially the tectonic plates and their boundaries. Using a double-page size digital topographic map of the Earth that includes both land and sea floor topography, students are asked to draw plate boundaries, deduce plate motions and interactions, and explore the connections between topography and tectonic processes at the global scale.

Greene, David

180

Digital interpolators for polar format processing. [of synthetic aperture radar images  

NASA Technical Reports Server (NTRS)

The polar format approach to SAR image formation requires data to be interpolated from a warped grid onto a Cartesian lattice. In general, this requires that data be interpolated between varying sampling rates. In this paper, frequency-domain optimality criteria for polar format interpolators are defined and justified, and an approach to designing the corresponding digital filters is described.

Adams, John W.; Hudson, Ralph E.; Bayma, Robert W.; Nelson, Jeffrey E.

1989-01-01

181

space Radar Image of Long Valley, California  

NASA Technical Reports Server (NTRS)

An area near Long Valley, California, was mapped by the Spaceborne Imaging Radar-C and X-band Synthetic Aperture Radar aboard the space shuttle Endeavor on April 13, 1994, during the first flight of the radar instrument, and on October 4, 1994, during the second flight of the radar instrument. The orbital configurations of the two data sets were ideal for interferometric combination -- that is overlaying the data from one image onto a second image of the same area to create an elevation map and obtain estimates of topography. Once the topography is known, any radar-induced distortions can be removed and the radar data can be geometrically projected directly onto a standard map grid for use in a geographical information system. The 50 kilometer by 50 kilometer (31 miles by 31 miles) map shown here is entirely derived from SIR-C L-band radar (horizontally transmitted and received) results. The color shown in this image is produced from the interferometrically determined elevations, while the brightness is determined by the radar backscatter. The map is in Universal Transverse Mercator (UTM) coordinates. Elevation contour lines are shown every 50 meters (164 feet). Crowley Lake is the dark feature near the south edge of the map. The Adobe Valley in the north and the Long Valley in the south are separated by the Glass Mountain Ridge, which runs through the center of the image. The height accuracy of the interferometrically derived digital elevation model is estimated to be 20 meters (66 feet) in this image. Spaceborne Imaging Radar-C and X-band Synthetic Aperture Radar (SIR-C/X-SAR) is part of NASA's Mission to Planet Earth. The radars illuminate Earth with microwaves, allowing detailed observations at any time, regardless of weather or sunlight conditions. SIR-C/X-SAR uses three microwave wavelengths: L-band (24 cm), C-band (6 cm) and X-band (3 cm). The multi-frequency data will be used by the international scientific community to better understand the global environment and how it is changing. The SIR-C/X-SAR data, complemented by aircraft and ground studies, will give scientists clearer insights into those environmental changes which are caused by nature and those changes which are induced by human activity. SIR-C was developed by NASA's Jet Propulsion Laboratory. X-SAR was developed by the Dornier and Alenia Spazio companies for the German space agency, Deutsche Agentur fuer Raumfahrtangelegenheiten (DARA), and the Italian space agency, Agenzia Spaziale Italiana (ASI), with the Deutsche Forschungsanstalt fuer Luft und Raumfahrt e.V.(DLR), the major partner in science, operations and data processing of X-SAR.

1994-01-01

182

Corneal topography  

Microsoft Academic Search

This paper explores the many aspects of the nature and measurement of the corneal surface. Its structure and the factors that influence it are described. The traditional techniques of keratometry are summarized and there is an emphasis on new experimental methods of determining corneal topography including moiré, holographic interferometric and profile techniques. The advantages and disadvantages of these procedures are

Thomas W. Smith

1977-01-01

183

High-Resolution Digital Mapping of Soil Surface Water Content at the Field Scale Using Ground Penetrating Radar  

NASA Astrophysics Data System (ADS)

Measuring soil surface water content spatial variability is essential for many environmental and agricultural researches and engineering applications, as this variable controls important key processes of the hydrological cycle such as infiltration, runoff, evaporation, and energy exchanges between the earth and the atmosphere. In particular, the characterization of spatial patterns and heterogeneities over a continuous range of scales is presently subject to intensive research for developing, calibrating and testing distributed hydrological models, with, e.g., the installation of field- to watershed-scale observatories. In that respect, ground penetrating radar (GPR) appears to be a promising tool for real-time, high resolution digital soil mapping at the field scale. Yet existing GPR techniques for quantitative soil characterization still suffer from a series of limitations, mainly arising from the strong simplifying assumptions that are commonly made with respect to electromagnetic wave propagation phenomena. We have developed a new GPR methodology based on full-waveform forward and inverse modelling, that inherently maximizes radar information retrieval capabilities thanks to an accurate electromagnetic model and system calibration procedure. The radar system consists of a vector network analyzer combined with an off- ground, zero-offset, ultra-wideband horn antenna, thereby setting up a stepped-frequency continuous-wave (SFCW) GPR. A full-waveform model describes accurately the radar signal by accounting for (1) all antenna effects and antenna-soil interactions through a linear system of frequency dependent, complex transfer functions, and (2) wave propagation in three-dimensional multilayered media through a Green's function as exact solution of Maxwell's equations. A fast procedure was developed to evaluate the involved spatial Green's function from its spectral counterpart, whose integral is singular. The soil electromagnetic properties and their vertical distribution are estimated by inverse modeling using various iterative optimization strategies, depending on the model complexity. The method presents especially considerable advantages compared to the current surface characterization techniques using GPR, namely, the ground wave and common reflection methods. The proposed methodology was successfully validated for a series of model configurations of increasing complexity. For the particular case of soil surface water content retrieval, we especially addressed the impact of shallow soil layering on the inverse estimates in case it is or not accounted for in the inverse model configuration. The results show that thin layers should not be neglected, especially when high contrasts between soil layers are encountered. The method is now routinely used for real-time, automated mapping of soil surface water content in the field. GPR-derived maps are compared to ground-truth measurements and satellite radar data products. Stochastic approaches are used for assessing the uncertainty on the inverse estimates. The proposed method constitutes in particular a robust alternative to other GPR approaches for shallow soil characterization.

Minet, J.; Lambot, S.; Slob, E.; Vereecken, H.; Vanclooster, M.

2009-05-01

184

Digital processing of orbital radar data to enhance geologic structure - Examples from the Canadian Shield  

Microsoft Academic Search

Various digital enhancement techniques for SAR are compared using SIR-B and Seasat images of the Canadian Shield. The three best methods for enhancing geological structure were found to be: (1) a simple linear contrast stretch; (2) a mean or median low-pass filter to reduce speckle prior to edge enhancement or a K nearest-neighbor average to cosmetically reduce speckle; and (3)

Penny M. Masuoka; Jeff Harris; Paul D. Lowman Jr.; Herbert W. Blodget

1988-01-01

185

The Surface Water and Ocean Topography Mission (SWOT): the Ka-band Radar Interferometer (KaRIn) for water level measurements at all scales  

NASA Astrophysics Data System (ADS)

The Surface Water and Ocean Topography (SWOT) mission will study ocean mesoscale and submesoscale phenomena and provide an inventory of storage change and discharge for fresh water bodies and rivers. In this paper, we examine the combination of measurements that will be used by SWOT to achieve a globally consistent data set. We introduce a new channel in the SWOT measurement that combines data transmitted by the interferometer antennas and received by the radiometer antenna allows the closing of the SWOT nadir coverage gap. This new mode also allows for improved calibration between the nadir altimeter and the interferometer, resulting in consistent range measurements. Consistency in the phase measurements is achieved using a mixture of cross-over calibration combined with optimal estimation of system error drift.

Rodriguez, Ernesto; Esteban-Fernandez, Daniel

2010-10-01

186

Repeat topography surveys of geomorphic changes using digital surface models deriving from Formosat-2 daily revisit stereo pair with very narrow baseline  

NASA Astrophysics Data System (ADS)

Repeat topography surveys provides a geometrically-corrected frame with relief information, which is crucial for studying geomorphic changes after a major slope hazard, such as the debris flow or landslides. The successful operation of Formosat-2 has proved the concept that the temporal resolution of a remote sensing system can be much improved by deploying a high-spatial-resolution sensor in a daily revisit orbit, as each accessible scene can be systematically observed from the same angle under similar illumination conditions. These characteristics make Formosat-2 an ideal satellite for site surveillance, and its images have been successfully applied in environmental monitoring, hazard assessment, orthomap generation, rapidly responding to a global disaster event, and land use management. The attempt of using a Formosat-2 stereo pair to generate a DSM, however, has not been very successful up-to-date. Ironically, it is mainly due to the characteristics of daily-revisit orbit as well. According to the parallax equation, to obtain an accurate height estimation requires a high disparity precision from the stereo pair. The most convenient approach is to maximize the baseline B or the baseline/height (B/H) ratio to a preferred range 0.6 to 1. It is not feasible, however, to acquire an across-track stereo pair with that range of baseline from the daily-revisit orbit using Formosat-2. Even taking the orbit drifting into consideration, it would take a few months to achieve a B/H ratio of approximately 0.15 across track. Another approach is to acquire an along-track stereo pair. But for the mountainous areas, such as the central mountain areas, in Taiwan, the shaded effect and geometrically distortion are apparent. This prohibits any attempt to employ the automatic image matching technique to generate a DSM based on the disparities retrieved from Frmosat-2 along-track stereo pair directly. Phase correlation is operated in the frequency-domain, which enables the relative translative offset between two similar images to be rapidly estimated. To meet the requirements in remote sensing and biomedical imaging, the technology of phase correlation has been extended to the sub-pixel level. Liu and Yan (2008) developed a robust phase correlation model using the based feature matching for image co-registration and DEM generation. Considering the fact that the Formosat-2 consecutive images are intrinsically stereo pairs with very narrow baselines, this innovative stereo-matching algorithm based on SPPC technique is employed to process Formosat-2 daily revisit stereo pairs with very narrow baselines. The detailed accuracy and efficiency analysis is investigated for the study area, Namasha, Kaohsiung, using the 50cm resolution aerial photo and the 2m resolution DEM derived from airborne LiDAR data. The archive of Formosat-2 images in Taiwan area collected from 2005 to 2012 was screened out, with the intention to select the consecutive pairs of those areas where major slope disasters occurred in the past eight years. This research encourages the repeated topography surveys of geomorphic changes using digital surface models deriving from Formosat-2 daily revisit stereo pair with very narrow baseline.

Liu, C.; Wen, H.; Liu, J.; Ko, M.; Yan, H.; Chang, L.

2012-12-01

187

Multidimensional radar picture  

NASA Astrophysics Data System (ADS)

In marine navigation systems, the three-dimensional (3D) visualization is often and often used. Echosonders and sonars working in hydroacustic systems can present pictures in three dimensions. Currently, vector maps also offer 3D presentation. This presentation is used in aviation and underwater navigation. In the nearest future three-dimensional presentation may be obligatory presentation in displays of navigation systems. A part of these systems work with radar and communicates with it transmitting data in a digital form. 3D presentation of radar picture require a new technology to develop. In the first step it is necessary to compile digital form of radar signal. The modern navigation radar do not present data in three-dimensional form. Progress in technology of digital signal processing make it possible to create multidimensional radar pictures. For instance, the RSC (Radar Scan Converter) - digital radar picture recording and transforming tool can be used to create new picture online. Using RSC and techniques of modern computer graphics multidimensional radar pictures can be generated. The radar pictures mentioned should be readable for ECDIS. The paper presents a method for generating multidimensional radar picture from original signal coming from radar receiver.

Waz, Mariusz

2010-05-01

188

Optimized Global Digital Elevation Data Records (Invited)  

NASA Astrophysics Data System (ADS)

The Shuttle Radar Topography Mission (SRTM) used radar interferometry to map the Earth's topography between ±60° latitude - representing 80% of the land surface. The resulting digital elevation models bettered existing topographic data sets (including restricted military data) in accuracy, areal coverage and uniformity by several orders of magnitude, and the resulting data records have found broad application in most of the geosciences, military operations, even Google Earth. Despite their popularity the SRTM data have several limitations, including lack of coverage in polar regions and occasional small voids, or areas of no data in regions of high slope of low radar backscatter. Fortunately additional data sets have become available that, although lacking SRTM's data quality, are sufficient to mitigate many of these limitations. Primary among these is the Global Digital Elevation Model (GDEM) produced from ASTER stereo pairs. The MEaSUREs program is sponsoring an effort to merge these sets to produce and distribute an improved collection of data records that will optimize the topographic data, as well as make available additional non-topographic data products from the SRTM mission. There are four main areas of effort: (1) A systematic program to combine SRTM elevation data with those from other sensors, principally GDEM but also including SPOT stereo, the USGS’s National Elevation Data Set and others, to fill voids in the DEMs according to a prioritized plan, as well as extend the coverage beyond the current 60° latitude limit. (2) Combine the topographic data records with ICESat laser altimeter topography profiles to produce and distribute data records with enhanced ground control. (3) Document the existing SRTM radar image and ancillary data records, as well as generate image mosaics at multiple scales and distribute them via the world wide web. (4) Generate, document and distribute a standard and representative set of SRTM raw radar echo data, along with the appropriate ancillary tracking and pointing data necessary to process the echoes into DEMS using improved algorithms or

Kobrick, M.; Farr, T.; Crippen, R. E.

2009-12-01

189

Space Radar Image of Owens Valley, California  

NASA Technical Reports Server (NTRS)

This is a three-dimensional perspective view of Owens Valley, near the town of Bishop, California that was created by combining two spaceborne radar images using a technique known as interferometry. Visualizations like this one are helpful to scientists because they clarify the relationships of the different types of surfaces detected by the radar and the shapes of the topographic features such as mountains and valleys. The view is looking southeast along the eastern edge of Owens Valley. The White Mountains are in the center of the image, and the Inyo Mountains loom in the background. The high peaks of the White Mountains rise more than 3,000 meters (10,000 feet) above the valley floor. The runways of the Bishop airport are visible at the right edge of the image. The meandering course of the Owens River and its tributaries appear light blue on the valley floor. Blue areas in the image are smooth, yellow areas are rock outcrops, and brown areas near the mountains are deposits of boulders, gravel and sand known as alluvial fans. The image was constructed by overlaying a color composite radar image on top of a digital elevation map. The radar data were taken by the Spaceborne Imaging Radar-C/X-band Synthetic Aperture Radar (SIR-C/X-SAR) on board the space shuttle Endeavour in October 1994. The digital elevation map was produced using radar interferometry, a process in which radar data are acquired on different passes of the space shuttle. The two data passes are compared to obtain elevation information. The elevation data were derived from a 1,500-km-long (930-mile) digital topographic map processed at JPL. Radar image data are draped over the topography to provide the color with the following assignments: red is L-band vertically transmitted, vertically received; green is C-band vertically transmitted, vertically received; and blue is the ratio of C-band vertically transmitted, vertically received to L-band vertically transmitted, vertically received. This image is centered near 37.4 degrees north latitude and 118.3 degrees west longitude. No vertical exaggeration factor has been applied to the data. SIR-C/X-SAR, a joint mission of the German, Italian, and the United States space agencies, is part of NASA's Mission to Planet Earth.

1999-01-01

190

An 8Bit 2-gigasample\\/second A\\/D converter multichip module for digital receiver demonstration on Navy AN\\/APS145 E2-C Airborne Early Warning Aircraft radar  

Microsoft Academic Search

This paper will discuss multichip module technology as it is applied to a prototype high performance direct digitizing channelized radar receiver system under development for the Navy's E2-C Airborne Early Warning Aircraft, which encompasses both analog signals at UHF frequencies and multigigahertz digital signals. Critical issues which arise in the design of such a system will be discussed, including thermal

R. L. Thompson; M. J. Degerstrom; W. L. Walters; M. E. Vickberg; P. J. Riemer; L. H. Amundsen; B. K. Gilbert

1998-01-01

191

The Application of RadarA~é Gauge Comparisons to Operational Precipitation Profile Corrections  

Microsoft Academic Search

The analyses of data recorded during the past eight years with two Swiss radars, a network of rain gauges, and river flow measurements have helped to quantify the vertical profile of reflectivity and the influences of topography, meteorology, and radar parameters on the precision of radar precipitation estimation. The influence of the topography around the radar, the width of the

Jürg Joss; Robert Lee

1995-01-01

192

The MST radar technique  

NASA Technical Reports Server (NTRS)

The coherent radar technique is reviewed with special emphasis to mesosphere-stratosphere-troposphere (MST) radars operating in the VHF band. Some basic introduction to Doppler radar measurements and the radar equation is followed by an outline of the characteristics of atmospheric turbulence, viewed from the scattering and reflection processes of radar signals. Radar signal acquisition and preprocessing, namely coherent detection, digital sampling, pre-integration and coding, is briefly discussed. The data analysis is represented in terms of the correlation and spectrum analysis, yielding the essential parameters: power, signal-to-noise ratio, average and fluctuating velocity and persistency. The techniques to measure wind velocities, viz. the different modes of the Doppler method as well as the space antenna method are surveyed and the feasibilities of the MST radar interferometer technique are elucidated. A general view on the criteria to design phased array antennas is given. An outline of the hardware of a typical MST radar system is presented.

Roettger, J.

1984-01-01

193

Shuttle Imaging Radar Experiment  

Microsoft Academic Search

The shuttle imaging radar (SIR-A) acquired images of a variety of the earth's geologic areas covering about 10 million square kilometers. Structural and geomorphic features such as faults, folds, outcrops, and dunes are clearly visible in both tropical and arid regions. The combination of SIR-A and Seasat images provides additional information about the surface physical properties: topography and roughness. Ocean

C. Elachi; J. B. Cimino; T. Dixon; D. L. Evans; J. P. Ford; R. S. Saunders; C. Breed; H. Masursky; J. F. McCauley; G. Schaber; L. Dellwig; A. England; H. MacDonald; P. Martin-Kaye; F. Sabins

1982-01-01

194

Decoders for MST radars  

NASA Technical Reports Server (NTRS)

Decoding techniques and equipment used by MST radars are described and some recommendations for new systems are presented. Decoding can be done either by software in special-purpose (array processors, etc.) or general-purpose computers or in specially designed digital decoders. Both software and hardware decoders are discussed and the special case of decoding for bistatic radars is examined.

Woodman, R. F.

1983-01-01

195

Target identification from radar signatures  

Microsoft Academic Search

Modern high resolution radar techniques and real time digital signal processing advances indicate the feasibility of extracting characteristic features of aircraft targets from their radar signatures. Two basic approaches have been suggested. The low frequency approach utilizes harmonically related radar frequencies with wavelengths comparable to the target dimensions. The microwave approach utilizes spread spectrum techniques to achieve high range resolution.

R. Strattan

1978-01-01

196

High-precision topography measurement through accurate in-focus plane detection with hybrid digital holographic microscope and white light interferometer module.  

PubMed

High-precision topography measurement of micro-objects using interferometric and holographic techniques can be realized provided that the in-focus plane of an imaging system is very accurately determined. Therefore, in this paper we propose an accurate technique for in-focus plane determination, which is based on coherent and incoherent light. The proposed method consists of two major steps. First, a calibration of the imaging system with an amplitude object is performed with a common autofocusing method using coherent illumination, which allows for accurate localization of the in-focus plane position. In the second step, the position of the detected in-focus plane with respect to the imaging system is measured with white light interferometry. The obtained distance is used to accurately adjust a sample with the precision required for the measurement. The experimental validation of the proposed method is given for measurement of high-numerical-aperture microlenses with subwavelength accuracy. PMID:24787417

Li?ewski, Kamil; Tomczewski, S?awomir; Kozacki, Tomasz; Kostencka, Julianna

2014-04-10

197

Density Isostasy and Topography  

NSDL National Science Digital Library

Density, Isostasy, and Topography Anne Egger, Stanford University The original activity Density, Isostasy, and Topography already exists within the SERC website. This page describes how this activity can be used ...

198

Spectral estimation for clutter processing in digital radars by Dimension-Adaptive Particle Swarm Optimization (DA-PSO)  

Microsoft Academic Search

Power spectrum estimation from radar data is essential for target detection. For instance, microburst causes detrimental effects on airplane performance, and hence its detection is critical. We compare auto-regression (AR), Periodogram, Kaiser windowed Periodogram, and multiple-signal-classification (MUSIC) methods for microburst clutter spectrum estimation. Given a long train of returned signal, we are able to segment the signal to obtain multiple

Lisa Ann Osadciw; Yanjun Yan

2009-01-01

199

Topography over South America from ERS altimetry  

NASA Technical Reports Server (NTRS)

The results of the surface topography mapping of South America during the ERS-1 geodetic mission are presented. The altimeter waveforms, the range measurement, and the internal and Doppler range corrections were obtained. The atmospheric corrections and solid tides were calculated. Comparisons between Shuttle laser altimetry and ERS-1 altimetry grid showed good agreement. Satellite radar altimetry data can be used to improve the topographic knowledge of regions for which only poor elevation data currently exist.

Brenner, Anita; Frey, Herb; DiMarzio, John; Tsaoussi, Lucia

1997-01-01

200

Mars topography harmonics and geophysical implications  

NASA Technical Reports Server (NTRS)

The paper describes an improved model of Martian global topography which has been obtained by fitting a sixteenth-degree harmonic series to occultation, radar, spectral, and photogrammetric measurements. Empirical elevation data based on photographic data are used to supplement the observations in areas without data. Values for the mean radius, the mean density, and the displacement of the center of the figure from the center of mass are presented. The reported geometric flattening is too great and the reported dynamic flattening is too small for Mars to be homogeneous and hydrostatic. Maps of the data distribution, global topography, and Bouguer gravity anomaly are interpreted in terms of a crustal thickness map which is consistent with gravity, topography, and recent preliminary Viking seismic results.

Bills, B. G.; Ferrari, A. J.

1978-01-01

201

Radar principles  

Microsoft Academic Search

The basic operating principles, design, and applications of radars are discussed in an introductory text intended for first-year graduate students. Topics addressed include radar measurements, radar target cross sections, radar detection, ground effects, matched filters, ambiguity functions, coded radar signals, and radar measurement accuracy. Consideration is given to processing coherent pulse trains, moving-target indicators, CFAR, SAR, and monopulse antenna tracking.

Nadav Levanon

1988-01-01

202

Synthetic aperture radar and interferometry development at Sandia National Laboratories  

SciTech Connect

Environmental monitoring, earth-resource mapping, and military systems require broad-area imaging at high resolutions. Many times the imagery must be acquired in inclement weather or during night as well as day. Synthetic aperture radar (SAR) provides such a capability. SAR systems take advantage of the long-range propagation characteristics of radar signals and the complex information processing capability of modern digital electronics to provide high resolution imagery. SAR complements photographic and other optical imaging capabilities because of the minimum constrains on time-of-day and atmospheric conditions and because of the unique responses of terrain and cultural targets to radar frequencies. Interferometry is a method for generating a three-dimensional image of terrain. The height projection is obtained by acquiring two SAR images from two slightly differing locations. It is different from the common method of stereoscopic imaging for topography. The latter relies on differing geometric projections for triangulation to define the surface geometry whereas interferometry relies on differences in radar propagation times between the two SAR locations. This paper presents the capabilities of SAR, explains how SAR works, describes a few SAR applications, provides an overview of SAR development at Sandia, and briefly describes the motion compensation subsystem.

NONE

1993-04-01

203

Digital Globe  

NSDL National Science Digital Library

Visitors to the Digital Globe have a front seat view of Lisbon, Portugal and the Phillipine Trench. The site offers two MPEG videos which animate topographic seafloor images. The video clips were created by David Sandwell at the Scripps Institution of Oceanography. Also available are nine images of seafloor topography from around the globe. Note that the videos are very large files.

204

Shuttle imaging radar experiment  

NASA Technical Reports Server (NTRS)

The Shuttle imaging radar (SIR-A) acquired images of a variety of the earth's geologic areas covering about 10 million square kilometers. Structural and geomorphic features such as faults, folds, outcrops, and dunes are clearly visible in both tropical and arid regions. The combination of SIR-A and Seasat images provides additional information about the surface physical properties: topography and roughness. Ocean features were also observed, including large internal waves in the Andaman Sea.

Elachi, C.; Brown, W. E.; Cimino, J. B.; Dixon, T.; Evans, D. L.; Ford, J. P.; Saunders, R. S.; Breed, C.; Masursky, H.; England, A.

1982-01-01

205

Venus topography - A harmonic analysis  

NASA Technical Reports Server (NTRS)

A model of Venusian global topography has been obtained by fitting an eighteenth-degree harmonic series to Pioneer Venus orbiter radar altimeter data. The mean radius is (6051.45 + or - 0.04) km. The corresponding mean density is (5244.8 + or 0.5) kg/cu m. The center of figure is displaced from the center of mass by (0.339 + or - 0.088) km towards (6.6 + or 10.1) deg N, (148. 8 + or - 7.7) deg. The figure of Venus is distinctly triaxial, but the orientation and magnitudes of the principal topographic axes correlate rather poorly with the gravitational principal axes. However, the higher-degree harmonics of topography and gravity are significantly correlated. The topographic variance spectrum of Venus is very similar in form to those of the moon, Mars, and especially earth. It is suggested that this spectral similarity simply reflects a statistical balance between constructional and degradational geomorphic proceses. Venus and earth are particularly similar (and differ from the moon and Mars) in that the larger bodies both exhibit a significant low degree deficit (relative to the extrapolated trend of the higher harmonics).

Bills, B. G.; Kobrick, M.

1985-01-01

206

In-flight detection of errors for enhanced aircraft flight safety and vertical accuracy improvement using digital terrain elevation data with an inertial navigation system, global positioning system and radar altimeter  

NASA Astrophysics Data System (ADS)

This dissertation discusses integration architectures using digital terrain elevation data (DTED) with an inertial navigation system (INS), a global positioning system (GPS) and a radar altimeter. Two integration architectures are considered: DTED with INS, GPS and radar altimeter for aircraft vertical accuracy improvement during the final approach; and DTED with kinematic GPS (KGPS) and a radar altimeter for enhanced aircraft flight safety. Error models were generated and verified with flight-test data. High-fidelity simulation was used to investigate vertical accuracy improvement. Improvement was found to be 1.2 meters, a reduction of 28.6% in the vertical error. Flight testing was performed to assess the feasibility of enhanced flight safety. Reasons for enhanced flight safety are twofold: (1) the ad-hoc integration of terrain elevation data into the cockpit conceivably may create scenarios which lead to accidents because the cockpit display is quite realistic, and (2) reduction of controlled flight into terrain (CFIT). The radar altimeter is the principle sensor used to compare navigation outputs with publicly available DTED. Results show that it is feasible to define an operationally useful probability of agreement, Pa, among KGPS, DTED and the radar altimeter, by using a mean-square-difference test statistic. This probability of agreement can be used to warn the pilot if the terrain depiction does not agree with the navigation solution provided by KGPS, thus enhancing flight safety.

Gray, Robert Anthony

207

Forward modeling of ground-penetrating radar data using digitized outcrop images and multiple scenarios of water saturation  

NASA Astrophysics Data System (ADS)

Simple petrophysical models and a sedimentologically interpreted outcrop photograph corresponding to the plane of a ground-penetrating radar (GPR) survey are combined to create models for the simulation of GPR. This makes possible the comparison of GPR field data, synthetic GPR sections, and a lithology image. On the basis of this comparison the usefulness of the method for identifying hydrologically significant lithofacies and the sensitivity of the results to different subsurface conditions may be investigated. In particular, GPR simulations are performed for an outcrop model at three states of water saturation: uniformly drained (uniform residual saturation), nonuniformly saturated, and fully saturated. As predicted by reflection coefficient calculations, comparison among the synthetic simulations highlights the importance of the existing pore water distribution in determining the "visibility" of lithologic elements in GPR sections. Comparisons of the synthetic GPR sections with the field data show overall agreement, though the occurrence of various observed reflections depends on the presence and distribution of pore water. Conclusions are also drawn about extending outcrop analog-derived results to investigations of real (fully saturated) aquifers.

Kowalsky, M. B.; Dietrich, P.; Teutsch, G.; Rubin, Y.

2001-06-01

208

Bistatic coherent radar receiving system  

NASA Astrophysics Data System (ADS)

A coherent-on-receive MTI radar receiver system for use with cooperative or non-cooperative radar transmitters of either the coherent or noncoherent, simple magnatron type and scanning antennas is discussed. The receiver includes coherent digital signal processing with provision for normalizing or compensating phase variations in the transmitter carrier pulses.

Yamano, L. C.

1984-10-01

209

Bistatic coherent radar receiving system  

Microsoft Academic Search

A coherent-on-receive MTI radar receiver system for use with cooperative or non-cooperative radar transmitters of either the coherent or noncoherent, simple magnatron type and scanning antennas is discussed. The receiver includes coherent digital signal processing with provision for normalizing or compensating phase variations in the transmitter carrier pulses.

L. C. Yamano

1984-01-01

210

Application of ground-penetrating radar, digital optical borehole images, and cores for characterization of porosity hydraulic conductivity and paleokarst in the Biscayne aquifer, southeastern Florida, USA  

USGS Publications Warehouse

This paper presents examples of ground-penetrating radar (GPR) data from two study sites in southeastern Florida where karstic Pleistocene platform carbonates that comprise the unconfined Biscayne aquifer were imaged. Important features shown on resultant GPR profiles include: (1) upward and lateral qualitative interpretative distribution of porosity and hydraulic conductivity; (2) paleotopographic relief on karstic subaerial exposure surfaces; and (3) vertical stacking of chronostratigraphic high-frequency cycles (HFCs). These characteristics were verified by comparison to rock properties observed and measured in core samples, and identified in digital optical borehole images. Results demonstrate that an empirical relation exists between measured whole-core porosity and hydraulic conductivity, observed porosity on digital optical borehole images, formation conductivity, and GPR reflection amplitudes-as porosity and hydraulic conductivity determined from core and borehole images increases, formation conductivity increases, and GPR reflection amplitude decreases. This relation allows for qualitative interpretation of the vertical and lateral distribution of porosity and hydraulic conductivity within HFCs. Two subtidal HFCs in the uppermost Biscayne aquifer have significantly unique populations of whole-core porosity values and vertical hydraulic conductivity values. Porosity measurements from one cycle has a median value about two to three times greater than the values from the other HFC, and median values of vertical hydraulic-conductivity about three orders of magnitude higher than the other HFC. The HFC with the higher porosity and hydraulic conductivity values is shown as a discrete package of relatively low-amplitude reflections, whereas the HFC characterized by lower porosity and hydraulic-conductivity measurements is expressed by higher amplitude reflections. Porosity and hydraulic-conductivity values measured from whole-core samples, and vuggy porosity identified on digital borehole images from shallowing-upward, peritidal HFCs show that the highest porosity occurs at the base of the cycles, moderate porosity at the middle of the cycles, and lowest porosity occurs at the top of cycles. Hydraulic conductivity is also highest at the base of the peritidal cycles and lowest in the middle to upper parts of cycles. This change in porosity and hydraulic conductivity from bottom to top is visible as an upward variation in reflection amplitude on GPR profiles-lowest amplitudes at the base and highest at the cycle tops. This study demonstrates that GPR can be used to show the qualitative distribution of porosity and hydraulic conductivity within a cycle-stratigraphic framework composed of carbonate HFCs. The distribution of porosity and hydraulic conductivity within HFCs is related to depositional textures. The upward and lateral patterns of the rock facies within the HFCs can be translated to geophysical-log properties and radar facies configurations that could aid in interpretation and prediction of ground-water flow through a carbonate aquifer. ?? 2003 Elsevier B.V. All rights reserved.

Cunningham, K. J.

2004-01-01

211

Goldstone radar contributions to Mars Pathfinder landing safety  

NASA Technical Reports Server (NTRS)

Goldstar radar can provide topography 'profiles', statistical surface roughness, and radar images within a few degrees of the sub-Earth point. Goldstone/Very Large Array (VLA) bistatic radar observations can image the whole disk of Mars with integration times on the order of ten min before pixel smearing occurs. Data from all these radar techniques can be useful for observing the local surface conditions relating to landing safety issues for Mars Pathfinder.

Slade, Martin A.; Jurgens, R. F.

1994-01-01

212

Radar principles  

NASA Astrophysics Data System (ADS)

The basic operating principles, design, and applications of radars are discussed in an introductory text intended for first-year graduate students. Topics addressed include radar measurements, radar target cross sections, radar detection, ground effects, matched filters, ambiguity functions, coded radar signals, and radar measurement accuracy. Consideration is given to processing coherent pulse trains, moving-target indicators, CFAR, SAR, and monopulse antenna tracking. Extensive diagrams and graphs are provided.

Levanon, Nadav

213

Impact of extremely high speed logic technology on radar performance  

Microsoft Academic Search

Limitations related to the utilization of digital procedures in radar systems are connected with the difference between the throughput rates of the digital devices and the required throughput rate for broadband, multiple-range-gated radar signals. The present investigation is concerned with the feasibility of innovative uses of extremely high speed integrated circuits in radar. The probable technologies for high speed electronics

E. K. Reedy; R. B. Efurd; M. N. Yoder

1982-01-01

214

Quantifying the Differences in Low Probability of Intercept Radar Waveforms Using Quadrature Mirror Filtering.  

National Technical Information Service (NTIS)

Low Probability of Intercept (LPI) radars are a class of radar systems that possess certain performance characteristics causing them to be nearly undetectable by most modern digital intercept receivers, Consequently, LPI radar systems can operate undetect...

P. Jarpa

2002-01-01

215

Error analysis in the digital elevation model of Kuwait desert derived from repeat pass synthetic aperture radar interferometry  

NASA Astrophysics Data System (ADS)

The aim of this paper is to analyze the errors in the Digital Elevation Models (DEMs) derived through repeat pass SAR interferometry (InSAR). Out of 29 ASAR images available to us, 8 are selected for this study which has unique data set forming 7 InSAR pairs with single master image. The perpendicular component of baseline (B highmod) varies between 200 to 400 m to generate good quality DEMs. The Temporal baseline (T) varies from 35 days to 525 days to see the effect of temporal decorrelation. It is expected that all the DEMs be similar to each other spatially with in the noise limits. However, they differ very much with one another. The 7 DEMs are compared with the DEM of SRTM for the estimation of errors. The spatial and temporal distribution of errors in the DEM is analyzed by considering several case studies. Spatial and temporal variability of precipitable water vapour is analysed. Precipitable water vapour (PWV) corrections to the DEMs are implemented and found to have no significant effect. The reasons are explained. Temporal decorrelation of phases and soil moisture variations seem to have influence on the accuracy of the derived DEM. It is suggested that installing a number of corner reflectors (CRs) and the use of Permanent Scatter approach may improve the accuracy of the results in desert test sites.

Rao, Kota S.; Al Jassar, Hala K.

2010-09-01

216

Crop Classification with a Landsat\\/Radar Sensor Combination  

Microsoft Academic Search

A combined Landsat\\/radar approach to classification of remotely sensed data, with emphasis on crops, was undertaken. Radar data were obtained by microwave radar spectrometers over fields near Eudora, Kansas and Landsat image data were obtained for the same test site. After Landsat digital images were registered and test-cells extracted, a comparable set of radar image pixels were simulated to match

Robert Y. Li; Fawwaz T. Ulaby; Ronald J. Eyton

1980-01-01

217

Derivation of model topography  

NASA Technical Reports Server (NTRS)

The Fourth-Order model necessitates representation of the topography. The problem of the representation of the topography at grid points is addressed. The attempted was to derive an envelope topography. The TI is obtained by taking local mean plus one standard deviation at each grid point and sigma filtering it. The method was greatly influenced by large standard deviations at steep mountains. The O1 topography is the local mean. The S1 is obtained by Sigma filtering in both latitude and longitude the mean O1. The S2 is when the operation is applied twice and S3 thrice, the Q3 is the sigma filtered local mean of the upper third quantile of the source data.

Balgovind, R. C.

1985-01-01

218

24 GHz radar front-end for FMCW and spread spectrum radar applications  

Microsoft Academic Search

Two configurations of radar front-end with a multi-chip assembly for automotive applications have been studied and presented. One configuration is suitable for both FMCW radar and spread spectrum radar with the replacement of a base-band module that could be realized by a digital synthesizer; the concept \\

Zhaolong Li; Ke Wu

2006-01-01

219

Classification of topography using DEM data and its correlation with the geology of Greece  

NASA Astrophysics Data System (ADS)

Continuous topography from Digital Elevation Model (DEM) data is frequently segmented into terrain classes based on local morphological characteristics of terrain elevation, e.g., local slope gradient and convexity. The resulting classes are often used as proxies for the average shear wave velocity up to 30 m, and the determination of ground types as required by the Eurocode (EC8) for computing elastic design spectra. In this work, we investigate the links between terrain related variables, particularly slope gradient, extracted for the area of Greece from the Shuttle Radar Topography Mission (SRTM) 30 arc second global topographic data available from the United States Geological Survey (USGS), with: (a) the global terrain classification product of Iwahashi and Pike (2007) in which 16 terrain types are identified for the same spatial resolution, and (b) information on geological units extracted at the same resolution from the geological map of Greece at a scale of 1/500000 as published from the Institute of Geology and Mineral Exploration (IGME). An interpretation of these links is presented within the context of understanding the reliability of using geology, slope and terrain classes for site characterizations of earthquake risk in a high seismicity area like Greece. Our results indicate that slope is a somewhat biased proxy for solid rocks, whereas in Alluvial deposits the distance to and type of the nearest geological formation appears to provide qualitative information on the size of the sedimentary deposit.

Zargli, Eleni; Liodakis, Stelios; Kyriakidis, Phaedon; Savvaidis, Alexandros

2013-08-01

220

Using 3D Printers to Model Earth Surface Topography for Increased Student Understanding and Retention  

NASA Astrophysics Data System (ADS)

In February 2000, the Space Shuttle Endeavour flew a specially modified radar system during an 11-day mission. The purpose of the multinational Shuttle Radar Topography Mission (SRTM) was to "obtain elevation data on a near-global scale to generate the most complete high-resolution digital topographic database of Earth" by using radar interferometry. The data and resulting products are now publicly available for download and give a view of the landscape removed of vegetation, buildings, and other structures. This new view of the Earth's topography allows us to see previously unmapped or poorly mapped regions of the Earth as well as providing a level of detail that was previously unknown using traditional topographic mapping techniques. Understanding and appreciating the geographic terrain is a complex but necessary requirement for middle school aged (11-14yo) students. Abstract in nature, topographic maps and other 2D renderings of the Earth's surface and features do not address the inherent spatial challenges of a concrete-learner and traditional methods of teaching can at times exacerbate the problem. Technological solutions such as 3D-imaging in programs like Google Earth are effective but lack the tactile realness that can make a large difference in learning comprehension and retention for these young students. First developed in the 1980's, 3D printers were not commercial reality until recently and the rapid rise in interest has driven down the cost. With the advent of sub US1500 3D printers, this technology has moved out of the high-end marketplace and into the local office supply store. Schools across the US and elsewhere in the world are adding 3D printers to their technological workspaces and students have begun rapid-prototyping and manufacturing a variety of projects. This project attempted to streamline the process of transforming SRTM data from a GeoTIFF format by way of Python code. The resulting data was then inputted into a CAD-based program for visualization and exporting as a .stl file for 3D printing. A proposal for improving the method and making it more accessible to middle school aged students is provided. Using the SRTM data to print a hand-held visual representation of a portion of the Earth's surface would utilize existing technology in the school and alter how topography can be taught in the classroom. Combining methods of 2D paper representations, on-screen 3D visualizations, and 3D hand-held models, give students the opportunity to truly grasp and retain the information being provided.

Thesenga, David; Town, James

2014-05-01

221

Radar applications overview  

NASA Astrophysics Data System (ADS)

During the fifty years since its initial development as a means of providing early warning of airborne attacks against allied countries during World War II, radar systems have developed to the point of being highly mobile and versatile systems capable of supporting a wide variety of remote sensing applications. Instead of being tied to stationary land-based sites, radar systems have found their way into highly mobile land vehicles as well as into aircraft, missiles, and ships of all sizes. Of all these applications, however, the most exciting revolution has occurred in the airborne platform arena where advanced technology radars can be found in all shapes and sizes...ranging from the large AWACS and Joint STARS long range surveillance and targeting systems to small millimeter wave multi-spectral sensors on smart weapons that can detect and identify their targets through the use of highly sophisticated digital signal processing hardware and software. This paper presents an overview of these radar applications with the emphasis on modern airborne sensors that span the RF spectrum. It will identify and describe the factors that influence the parameters of low frequency and ultra wide band radars designed to penetrate ground and dense foliage environments and locate within them buried mines, enemy armor, and other concealed or camouflaged weapons of war. It will similarly examine the factors that lead to the development of airborne radar systems that support long range extended endurance airborne surveillance platforms designed to detect and precision-located both small high speed airborne threats as well as highly mobile time critical moving and stationary surface vehicles. The mission needs and associated radar design impacts will be contrasted with those of radar systems designed for high maneuverability rapid acquisition tactical strike warfare platforms, and shorter range cued air-to-surface weapons with integral smart radar sensors.

Greenspan, Marshall

1996-06-01

222

Radar frequency radiation  

NASA Astrophysics Data System (ADS)

A method is presented for the determination of radar frequency radiation power densities that the PAVE PAWS radar system could produce in its air and ground environment. The effort was prompted by the concern of the people in the vicinity of OTIS AFB MA and BEALE AFB CA about the possible radar frequency radiation hazard of the PAVE PAWS radar. The method is based on the following main assumptions that: (a) the total field can be computed as the vector summation of the individual fields due to each antenna element; (b) the individual field can be calculated using distances for which the field point is in the far field of the antenna element. An RFR computer program was coded for the RADC HE 6180 digital computer and exercised to calculate the radiation levels in the air and ground space for the present baseline and the possible Six DB and 10 DB growth systems of the PAVE PAWS radar system at OTIS AFB MA. The average radiation levels due to the surveillance fence were computed for three regions: in the air space in front of the radar, at the radar hazard fence at OTIS AFB MA and at representative ground points in the OTIS AFB vicinity. It was concluded that the radar frequency radiation of PAVE PAWS does not present a hazard to personnel provided there is no entry to the air hazard zone or to the area within the hazard fence. The method developed offers a cost effective way to determine radiation levels from a phased array radar especially in the near field and transition regions.

Malowicki, E.

1981-11-01

223

Topography-assisted photoablation  

NASA Astrophysics Data System (ADS)

Topography assisted photoablation (TAP) is an important and logic step for future customized therapeutic photokeratectomy. Its goal is to reshape any irregular corneal surface in order to achieve an ideal sphere. Accuracy and reproducibility of the 2D and 3D topography data, strategies of data acquisition, data modification and transfer are essential elements. Accurate and appropriate subtraction methods for difference mapping are discussed. Furthermore, the properties and algorithms of the lasers' delivery systems, have to be taken into account. The overview paper describes and discusses some of the central elements of TAP.

Jean, Benedikt J.; Bende, Thomas

1999-06-01

224

Radar ice motion interferometry  

NASA Technical Reports Server (NTRS)

Tandem pairs of ERS-1/2 radar observations of the Jakobshavn glacier, in Greenland, were used to estimate the ice motion. Interferograms are made from two such pairs, separated by the 35 day repeat cycle. Motion can be estimated from these without knowledge of the local topography. Although the temporal baseline of the interferograms was only one day, the correlation from the fast moving ice was very low. Because of the resulting phase noise, a scene-dependent filter was used to help unwrap the interferograms. For the upper part of the glacier, the filter worked well. The filter and the measured ice motion are presented.

Goldstein, Richard; Werner, Charles

1997-01-01

225

OpenTopography: Enabling Online Access to High-Resolution Lidar Topography Data and Processing Tools  

NASA Astrophysics Data System (ADS)

High-resolution topography data acquired with lidar (light detection and ranging) technology are revolutionizing the way we study the Earth's surface and overlying vegetation. These data, collected from airborne, tripod, or mobile-mounted scanners have emerged as a fundamental tool for research on topics ranging from earthquake hazards to hillslope processes. Lidar data provide a digital representation of the earth's surface at a resolution sufficient to appropriately capture the processes that contribute to landscape evolution. The U.S. National Science Foundation-funded OpenTopography Facility (http://www.opentopography.org) is a web-based system designed to democratize access to earth science-oriented lidar topography data. OpenTopography provides free, online access to lidar data in a number of forms, including the raw point cloud and associated geospatial-processing tools for customized analysis. The point cloud data are co-located with on-demand processing tools to generate digital elevation models, and derived products and visualizations which allow users to quickly access data in a format appropriate for their scientific application. The OpenTopography system is built using a service-oriented architecture (SOA) that leverages cyberinfrastructure resources at the San Diego Supercomputer Center at the University of California San Diego to allow users, regardless of expertise level, to access these massive lidar datasets and derived products for use in research and teaching. OpenTopography hosts over 500 billion lidar returns covering 85,000 km2. These data are all in the public domain and are provided by a variety of partners under joint agreements and memoranda of understanding with OpenTopography. Partners include national facilities such as the NSF-funded National Center for Airborne Lidar Mapping (NCALM), as well as non-governmental organizations and local, state, and federal agencies. OpenTopography has become a hub for high-resolution topography resources. Datasets hosted by other organizations, as well as lidar-specific software, can be registered into the OpenTopography catalog, providing users a "one-stop shop" for such information. With several thousand active users, OpenTopography is an excellent example of a mature Spatial Data Infrastructure system that is enabling access to challenging data for research, education and outreach. Ongoing OpenTopography design and development work includes the archive and publication of datasets using digital object identifiers (DOIs); creation of a more flexible and scalable high-performance environment for processing of large datasets; expanded support for satellite and terrestrial lidar; and creation of a "pluggable" infrastructure for third-party programs and algorithms. OpenTopography has successfully created a facility for sharing lidar data. In the project's next phase, we are working to enable equally easy and successful sharing of services for processing and analysis of these data.

Crosby, Christopher; Nandigam, Viswanath; Baru, Chaitan; Arrowsmith, J. Ramon

2013-04-01

226

Resistivity modelling with topography  

NASA Astrophysics Data System (ADS)

A major difficulty of electrical resistivity forward modelling is the singularity of the potential occurring at the source location. To avoid large numerical errors, the potential is split into a primary part containing the singularity and a secondary part. The primary potential is defined analytically for flat topography, and is classically computed numerically in the presence of topography: in that case, an accurate solution requires expensive computations. We propose to define the primary potential as the analytic solution valid for a homogeneous model and flat topography, and to modify accordingly the free surface boundary condition for the secondary potential, such that the overall potential still satisfies the Poisson equation. The modified singularity removal technique thus remains fully efficient for any acquisition geometries, without any additional numerical computation, and also applicable in the presence of a buried cavity. This approach is implemented with the generalized finite difference method developed on unstructured meshes and validated through the comparison with analytical solutions. Finally, we illustrate in simple 2-D and 3-D cases how the potential depends on the shape of the topography and on the electrode positions.

Penz, Sébastien; Chauris, Hervé; Donno, Daniela; Mehl, Caroline

2013-09-01

227

Flow Interaction with Topography  

NSDL National Science Digital Library

This module explores the fundamental concepts used to determine how air flow interacts with topography. Using the simple analogy of a marble rolling over a hill, this module examines the relationship between wind speed and static stability of the atmosphere. These results are further extended to include three-dimensional terrain barriers as well as the evolution through time of the interaction.

Spangler, Tim

1999-05-01

228

Long wavelength gravity and topography anomalies  

NASA Technical Reports Server (NTRS)

It is shown that gravity and topography anomalies on the earth's surface may provide new information about deep processes occurring in the earth, such as those associated with mantle convection. Two main reasons are cited for this. The first is the steady improvement that has occurred in the resolution of the long wavelength gravity field, particularly in the wavelength range of a few hundred to a few thousand km, mainly due to increased coverage of terrestrial gravity measurements and the development of radar altimeters in orbiting satellites. The second reason is the large number of numerical and laboratory experiments of convection in the earth, including some with deformable upper and lower boundaries and temperature-dependent viscosity. The oceans are thought to hold the most promise for determining long wavelength gravity and topography anomalies, since their evolution has been relatively simple in comparison with that of the continents. It is also shown that good correlation between long wavelength gravity and topography anomalies exists over some portions of the ocean floor

Watts, A. B.; Daly, S. F.

1981-01-01

229

Radar Studies in the Solar System  

NASA Technical Reports Server (NTRS)

We aid in a study of the solar system by means of ground-based radar. We have concentrated on (1) developing the ephemerides needed to acquire radar data at Arecibo Observatory and (2) analyzing the resultant data to: test fundamental laws of gravitation; determine the size, shape, topography, and spin vectors of the targets; and study the surface properties of these objects, through their scattering law and polarization characteristics.

Shapiro, Irwin I.

1996-01-01

230

Radar Entomology  

NSDL National Science Digital Library

Radar tracking used to profile insect migration, mating and flight patterns. Many links to various pages include current workers in radar entomology, historical uses of the technology, and many images.

0002-11-30

231

Radar Images of the Earth and the World Wide Web  

NASA Technical Reports Server (NTRS)

A perspective of NASA's Jet Propulsion Laboratory as a center of planetary exploration, and its involvement in studying the earth from space is given. Remote sensing, radar maps, land topography, snow cover properties, vegetation type, biomass content, moisture levels, and ocean data are items discussed related to earth orbiting satellite imaging radar. World Wide Web viewing of this content is discussed.

Chapman, B.; Freeman, A.

1995-01-01

232

Pioneer Venus Orbiter Radar Mapper - Design and operation  

Microsoft Academic Search

The Radar Mapper Experiment, carried aboard the Pioneer Venus Orbiter spacecraft, is designed to obtain a near-global picture of the topography, meter-scale surface slopes and reflectivity of Venus. Constraints imposed by the choice of orbit limit radar coverage to a latitude band lying between 74 deg N and 61 deg S completely around the planet. In addition to the altimetry

G. H. Pettengill; D. F. Horwood; C. H. Keller

1980-01-01

233

Lava flow surface roughness and depolarized radar scattering  

Microsoft Academic Search

Surface roughness has a strong controlling influence on radar scattering and other types of remote sensing observations. We compare field measurements of surface topography and dielectric constant for a range of lava flow textures to aircraft multipolarization radar observations at 5.7, 24, and 68 cm (C, L, and P band) wavelengths. The roughness is found to vary with scale in

Bruce A. Campbell; Michael K. Shepard

1996-01-01

234

Onboard Interferometric SAR Processor for the Ka-Band Radar Interferometer (KaRIn)  

NASA Technical Reports Server (NTRS)

An interferometric synthetic aperture radar (SAR) onboard processor concept and algorithm has been developed for the Ka-band radar interferometer (KaRIn) instrument on the Surface and Ocean Topography (SWOT) mission. This is a mission- critical subsystem that will perform interferometric SAR processing and multi-look averaging over the oceans to decrease the data rate by three orders of magnitude, and therefore enable the downlink of the radar data to the ground. The onboard processor performs demodulation, range compression, coregistration, and re-sampling, and forms nine azimuth squinted beams. For each of them, an interferogram is generated, including common-band spectral filtering to improve correlation, followed by averaging to the final 1 1-km ground resolution pixel. The onboard processor has been prototyped on a custom FPGA-based cPCI board, which will be part of the radar s digital subsystem. The level of complexity of this technology, dictated by the implementation of interferometric SAR processing at high resolution, the extremely tight level of accuracy required, and its implementation on FPGAs are unprecedented at the time of this reporting for an onboard processor for flight applications.

Esteban-Fernandez, Daniel; Rodriquez, Ernesto; Peral, Eva; Clark, Duane I.; Wu, Xiaoqing

2011-01-01

235

Radar principles  

NASA Technical Reports Server (NTRS)

Discussed here is a kind of radar called atmospheric radar, which has as its target clear air echoes from the earth's atmosphere produced by fluctuations of the atmospheric index of refraction. Topics reviewed include the vertical structure of the atmosphere, the radio refractive index and its fluctuations, the radar equation (a relation between transmitted and received power), radar equations for distributed targets and spectral echoes, near field correction, pulsed waveforms, the Doppler principle, and velocity field measurements.

Sato, Toru

1989-01-01

236

Backscattered Waveform Analysis By Using A New Radar Altimeter Simulator For Envisat  

Microsoft Academic Search

Radar Altimeters (RA) are designed to analyze the topography of the ocean surface. Envisat Radar Altimeter-2 (RA2) is a new breed of radar altimeter with increased capability due to on board Model Free Tracker (MFT). Increased stability, ability to follow continuous slopes and maintaining lock on rougher surfaces are important benefits of MFT. RA2 has a resolution of 400 m

B. Osmanoglu; M. Kartal; S. Wdowinski; T. Dixon

2005-01-01

237

Spaceborne imaging radar on EOS  

NASA Technical Reports Server (NTRS)

A multiparameter synthetic aperture imaging radar is planned as a facility instrument for the Earth Orbiting System (EOS). This sensor will operate at L, C, and X and at all possible polarizations (HH, VV, HV, VH), thus allowing the acquisition of detailed information about the surface physical and electrical properties. When combined with the visible and IR imaging spectrometry data and the surface topography, a full description of the surface structure, composition, thermal properties and physical properties could then be extracted.

Elachi, Charles; Cimino, J. B.

1987-01-01

238

Space Radar Image Isla Isabela in 3-D  

NASA Technical Reports Server (NTRS)

This is a three-dimensional view of Isabela, one of the Galapagos Islands located off the western coast of Ecuador, South America. This view was constructed by overlaying a Spaceborne Imaging Radar-C/X-band Synthetic Aperture Radar (SIR-C/X-SAR) image on a digital elevation map produced by TOPSAR, a prototype airborne interferometric radar which produces simultaneous image and elevation data. The vertical scale in this image is exaggerated by a factor of 1.87. The SIR-C/X-SAR image was taken on the 40th orbit of space shuttle Endeavour. The image is centered at about 0.5 degree south latitude and 91 degrees west longitude and covers an area of 75 by 60 kilometers (47 by 37 miles). The radar incidence angle at the center of the image is about 20 degrees. The western Galapagos Islands, which lie about 1,200 kilometers (750 miles)west of Ecuador in the eastern Pacific, have six active volcanoes similar to the volcanoes found in Hawaii and reflect the volcanic processes that occur where the ocean floor is created. Since the time of Charles Darwin's visit to the area in 1835, there have been more than 60 recorded eruptions on these volcanoes. This SIR-C/X-SAR image of Alcedo and Sierra Negra volcanoes shows the rougher lava flows as bright features, while ash deposits and smooth pahoehoe lava flows appear dark. Vertical exaggeration of relief is a common tool scientists use to detect relationships between structure (for example, faults, and fractures) and topography. Spaceborne Imaging Radar-C and X-Synthetic Aperture Radar (SIR-C/X-SAR) is part of NASA's Mission to Planet Earth. The radars illuminate Earth with microwaves allowing detailed observations at any time, regardless of weather or sunlight conditions. SIR-C/X-SAR uses three microwave wavelengths: L-band (24 cm), C-band (6 cm) and X-band (3 cm). The multi-frequency data will be used by the international scientific community to better understand the global environment and how it is changing. The SIR-C/X-SAR data, complemented by aircraft and ground studies, will give scientists clearer insights into those environmental changes which are caused by nature and those changes which are induced by human activity. SIR-C was developed by NASA's Jet Propulsion Laboratory. X-SAR was developed by the Dornier and Alenia Spazio companies for the German space agency, Deutsche Agentur fuer Raumfahrtangelegenheiten (DARA), and the Italian space agency, Agenzia Spaziale Italiana (ASI).

1999-01-01

239

Challenges to Airborne and Orbital Radar Sounding in the Presence of Surface Clutter: Lessons Learned (so far) from the Dry Valleys of Antarctica  

NASA Astrophysics Data System (ADS)

The search for life and in-situ resources for exploration on Mars targets both liquid and solid water, whether distributed or in reservoirs. Massive surface ice may cover potential habitats or other features of great interest. Ice-rich layering in the high latitudes holds clues to the climatic history of the planet. Multiple geophysical methods will clearly be necessary to fully characterize these various states of water (and other forms of ice), but radar sounding will be a critical component of the effort. Orbital radar sounders are already being employed and plans for surface-based and suborbital, above-surface radar sounders are being discussed. The difficulties in interpreting data from each type of platform are quite different. Given the lack of existing orbital radar sounding data from any planetary body, the analysis of airborne radar sounding data is quite useful for assessing the advantages and disadvantages of above-surface radar sounding on Mars. In addition to over 300,000 line-km of data collected over the Antarctic ice sheet by airborne radar sounding, we have recently analyzed data from the Dry Valleys of Antarctica where conditions and features emulate Mars in several respects. These airborne radar sounding data were collected over an ice-free area of Taylor Valley, ice-covered lakes, Taylor Glacier, and Beacon Valley. The pulsed radar (52.5 - 67.5 MHz chirp) was coherently recorded. Pulse compression and unfocused SAR processing were applied. One of the most challenging aspects of above-surface radar sounding is the determination of echo sources. This can, of course, be problematic for surface-based radar sounders given possible subsurface scattering geometries, but it is most severe for above-surface sounders because echoes from cross-track surface topography (surface clutter) can have similar time delays to those from the subsurface. We have developed two techniques to accomplish the identification of this surface clutter in single-pass airborne radar sounding data. The first technique simulates radar data using a digital elevation model (DEM) of surface topography to predict the location and shape of surface echoes in the radar data. This is complemented by the cross-track migration of radar echoes onto the surface. These migrated echoes are superimposed on imagery in order to correlate them with potential surface sources. Using these techniques enabled us to identify a number of echoes in a 24-km segment of the Dry Valleys flight path as arising from the surface and to identify subsurface echoes under the main trunk of Taylor Glacier and possibly multiple reflectors beneath the toe of Taylor Glacier. Surface-based radar confirms the thickness of the glacier at three crossing points. In the ice-free section of the test segment no real subsurface reflectors were found, indicating that the electromagnetic properties of the ground there do not allow significant radar penetration at 60 MHz and/or no radar-significant subsurface interfaces exist. These results illustrate the importance of using complementary techniques, the usefulness of a DEM, and the limitations of single-pass radar sounding data. Advanced processing techniques utilizing radar phase information show promise for achieving better clutter removal for single-pass data. Multi-pass data that we recently collected in the Dry Valleys should allow for the development of techniques to reduce or eliminate the need for a surface elevation model.

Holt, J. W.; Peters, M. E.; Kempf, S. D.; Morse, D. L.; Blankenship, D. D.

2005-12-01

240

A radar image time series  

NASA Technical Reports Server (NTRS)

A set of ten side-looking radar images of a mining area in Arizona that were aquired over a period of 14 yr are studied to demonstrate the photogrammetric differential-rectification technique applied to radar images and to examine changes that occurred in the area over time. Five of the images are rectified by using ground control points and a digital height model taken from a map. Residual coordinate errors in ground control are reduced from several hundred meters in all cases to + or - 19 to 70 m. The contents of the radar images are compared with a Landsat image and with aerial photographs. Effects of radar system parameters on radar images are briefly reviewed.

Leberl, F.; Fuchs, H.; Ford, J. P.

1981-01-01

241

Radar image of Rio Sao Francisco, Brazil  

NASA Technical Reports Server (NTRS)

This radar image acquired by SRTM shows an area south of the Sao Francisco River in Brazil. The area is predominantly scrub forest. Areas such as these are difficult to map by traditional methods because of frequent cloud cover and local inaccessibility. Image brightness differences in this image are caused by differences in vegetation type and density. Tributaries of the Sao Francisco are visible in the upper right. The Sao Francisco River is a major source of water for irrigation and hydroelectric power. Mapping such regions will allow scientists to better understand the relationships between flooding cycles, forestation and human influences on ecosystems.

This radar image was obtained by the Shuttle Radar Topography Mission as part of its mission to map the Earth's topography. The image was acquired by just one of SRTM's two antennas, and consequently does not show topographic data but only the strength of the radar signal reflected from the ground. This signal, known as radar backscatter, provides insight into the nature of the surface, including its roughness, vegetation cover, and urbanization.

The Shuttle Radar Topography Mission (SRTM), launched on February 11, 2000, uses the same radar instrument that comprised the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR) that flew twice on the Space Shuttle Endeavour in 1994. The mission is designed to collect three-dimensional measurements of the Earth's surface. To collect the 3-D data, engineers added a 60-meter-long (200-foot) mast, an additional C-band imaging antenna and improved tracking and navigation devices. The mission is a cooperative project between the National Aeronautics and Space Administration (NASA), the National Imagery and Mapping Agency (NIMA) and the German and Italian space agencies. It is managed by NASA's Jet Propulsion Laboratory, Pasadena, CA, for NASA's Earth Science Enterprise, Washington, DC.

2000-01-01

242

Digital communications study  

NASA Technical Reports Server (NTRS)

Research is reported dealing with problems of digital data transmission and computer communications networks. The results of four individual studies are presented which include: (1) signal processing with finite state machines, (2) signal parameter estimation from discrete-time observations, (3) digital filtering for radar signal processing applications, and (4) multiple server queues where all servers are not identical.

Boorstyn, R. R.

1973-01-01

243

Wireless Networks for Beamforming in Distributed Phased Array Radar.  

National Technical Information Service (NTIS)

The Wirelessly Networked Aperstructure Digital Phased Array Radar (WNADPAR) applies three relatively new concepts: Opportunistic, Aperstructure, and Wirelessly Networked Digital Architecture concepts. Using this approach almost the full length of the ship...

J. S. Noris

2007-01-01

244

Radar Interferometer for Topographic Mapping of Glaciers and Ice Sheets  

NASA Technical Reports Server (NTRS)

A report discusses Ka-band (35-GHz) radar for mapping the surface topography of glaciers and ice sheets at high spatial resolution and high vertical accuracy, independent of cloud cover, with a swath-width of 70 km. The system is a single- pass, single-platform interferometric synthetic aperture radar (InSAR) with an 8-mm wavelength, which minimizes snow penetration while remaining relatively impervious to atmospheric attenuation. As exhibited by the lower frequency SRTM (Shuttle Radar Topography Mission) AirSAR and GeoSAR systems, an InSAR measures topography using two antennas separated by a baseline in the cross-track direction, to view the same region on the ground. The interferometric combination of data received allows the system to resolve the pathlength difference from the illuminated area to the antennas to a fraction of a wavelength. From the interferometric phase, the height of the target area can be estimated. This means an InSAR system is capable of providing not only the position of each image point in along-track and slant range as with a traditional SAR but also the height of that point through interferometry. Although the evolution of InSAR to a millimeter-wave center frequency maximizes the interferometric accuracy from a given baseline length, the high frequency also creates a fundamental problem of swath coverage versus signal-to-noise ratio. While the length of SAR antennas is typically fixed by mass and stowage or deployment constraints, the width is constrained by the desired illuminated swath width. As the across-track beam width which sets the swath size is proportional to the wavelength, a fixed swath size equates to a smaller antenna as the frequency is increased. This loss of antenna size reduces the two-way antenna gain to the second power, drastically reducing the signal-to-noise ratio of the SAR system. This fundamental constraint of high-frequency SAR systems is addressed by applying digital beam-forming (DBF) techniques to synthesize multiple simultaneous receive beams in elevation while maintaining a broad transmit illumination. Through this technique, a high antenna gain on receive is preserved, thereby reducing the required transmit power and thus enabling high-frequency SARs and high-precision InSAR from a single spacecraft.

Moller, Delwyn K.; Sadowy, Gregory A.; Rignot, Eric J.; Madsen, Soren N.

2007-01-01

245

Velocity Compensation in Stepped Frequency Radar.  

National Technical Information Service (NTIS)

As compared to the commonly used constant frequency radar waveforms, the stepped-frequency waveform can achieve high range resolution while still retaining the advantages of lower instantaneous receiver bandwidth and lower analog-to-digital sampling rate....

Y. B. Ma

1995-01-01

246

Data volume reduction for imaging radar polarimetry  

NASA Technical Reports Server (NTRS)

Two alternative methods are presented for digital reduction of synthetic aperture multipolarized radar data using scattering matrices, or using Stokes matrices, of four consecutive along-track pixels to produce averaged data for generating a synthetic polarization image.

Zebker, Howard A. (inventor); Held, Daniel N. (inventor); Vanzyl, Jakob J. (inventor); Dubois, Pascale C. (inventor); Norikane, Lynne (inventor)

1988-01-01

247

Transmitter Noise Cancellation in Monostatic FMCW Radar  

Microsoft Academic Search

Digital leakage cancellation realizes noise cancellation at RF frequency, in addition to suppress leakage signal in FMCW monostatic radar. Noise cancellation mechanism is analyzed with autocorrelation function of noise. The measurement results in Ka band radar test are provided and show the effectiveness

Kaihui LinandYuanxun; Yuanxun Ethan Wang

2006-01-01

248

Radar: the evolution since World War II  

Microsoft Academic Search

Modern radar design has benefited from the evolution of specialized digital processing, allowing high resolution ground mapping, target identification, and target tracking under many conditions. Air-to-air interception makes use of complex decision processes to select from many modes that depend on the clutter backgrounds and flight profiles. Today's multimode radars provide this information for each task while minimizing distractions. Fire

R. Strong

2005-01-01

249

Satellite radar interferometry - Two-dimensional phase unwrapping  

Microsoft Academic Search

Interferometric synthetic aperture radar observations provide a means for obtaining high-resolution digital topographic maps from measurements of amplitude and phase of two complex radar images. The phase of the radar echoes may only be measured modulo 2 pi; however, the whole phase at each point in the image is needed to obtain elevations. An approach to 'unwrapping' the 2 pi

Richard M. Goldstein; Howard A. Zebker; Charles L. Werner

1988-01-01

250

The ambiguity function of the step frequency radar signal processor  

Microsoft Academic Search

In step frequency radar, the frequency of each pulse is increased in steps to achieve large effective bandwidth sequentially instead of instantaneously and thus easing the requirements on the analog to digital converter (ADC) and other hardware. This paper discusses the step frequency radar and its associated signal processing, and it investigates this type of radar with the ambiguity function.

G. S. Gill; Jen-Chih Huang

1996-01-01

251

Corneal topography system  

NASA Astrophysics Data System (ADS)

A new corneal topography system is described which combines proven grid projection and stereo triangulation techniques with an innovative user interface which simplifies the data capture process. Principles of the imaging, measurement, and calibration processes used with the system are presented. The device generates a complete topographic model of the anterior corneal surface with spatial resolution of 0.2 millimeters and elevation accuracy of 2 microns. System applications include pre- and post-operative assessment of refractive surgery patients, contact lens fitting including specification of custom RGP lenses, and excimer surgery planning and simulation. The innovative features of the system are described along with preliminary results of accuracy evaluations.

Cambier, James L.; Gao, Yan

1998-03-01

252

Radar - Principles, technology, applications  

NASA Astrophysics Data System (ADS)

An overview of modern radar is presented. The topics addressed include: functions and parameters of the radar system, the radar equation, targets and interfering signals, target echo information extraction, tracking radar, radar transmitters and microwave components, radar antennas, receivers and displays, radar signal processing, high resolution radar.

Edde, Byron

253

Evolution of Neogene Dynamic Topography in Africa  

NASA Astrophysics Data System (ADS)

The characteristic basins and swells of Africa's surface topography probably reflect patterns of convective circulation in the sub-lithospheric mantle. We have interrogated drainage networks to determine the spatial and temporal pattern of convectively driven uplift. ~560 longitudinal river profiles were extracted from a digital elevation model of Africa. An inverse model is then used to minimise the misfit between observed and calculated river profiles as a function of uplift rate history. During inversion, the residual misfit decreases from ~22 to ~5. Our results suggest that Africa's topography began to grow most rapidly after ~30 Ma at peak uplift rates of 0.1-0.15 mm/yr. The algorithm resolves distinct phases of uplift which generate localized swells of high topography and relief (e.g. the Angolan Dome). Uplift rate histories are shown to vary significantly from swell to swell. The calculated magnitudes, timing, and location of uplift agree well with local independent geological constraints, such as intense volcanism at Hoggar (42-39 Ma) and Afar (31-29 Ma), uplifted marine terraces, and warped peneplains. We have also calculated solid sediment flux histories for major African deltas which have persisted through time. This onshore record provides an important indirect constraint on the history of vertical motions at the surface, and agrees well with the offshore flux record, obtained from mapping isopachs of deltaic sediments. Our modelling and reconstructed sedimentary flux histories indicate that the evolution of drainage networks may contain useful information about mantle convective processes.

Paul, Jonathan; Roberts, Gareth; White, Nicky

2013-04-01

254

Radar observables  

NASA Astrophysics Data System (ADS)

A comprehensive account is given of missile design considerations relevant to the prediction, control, and measurement of airframe radar cross sections (RCSs), with a view to the minimization of missile observability. RCS reduction may proceed through airframe shaping to deflect incident radar emissions, as well as through the use of radar-absorbing surface materials and the devision of active radar signal-cancellation methods; some combination of these is often required, due to the deficiencies of any one method. The interaction of all RCS-reduction methods with airframe aerodynamic-design criteria are stressed.

Knott, Eugene F.

255

Stereo Pair: Inverted Topography, Patagonia, Argentina  

NASA Technical Reports Server (NTRS)

The Meseta de Somuncura is a broad plateau capped by basalt. Near its western edge is evidence of multiple volcanic events and a complex erosion history. Most notable are the long, narrow-, and winding lava flows that run across most of the right side of the image. These formed from low-viscosity lava that flowed down gullies over fairly flat terrain. Later, erosion of the landscape continued and the solidified flows were more resistant than the older surrounding rocks. Consequently, the flows became the ridges we see here. This natural process of converting gullies to ridges is called topographic inversion. See image PIA02755 (upper left corner) for a good example of topographic inversion in its earlier stages.

Other features seen here include numerous and varied closed depressions. The regional drainage is not well integrated, and drainage ends up in salty lakes (blue if shallow, black if deep). Wind streaks indicate that winds blow toward the east (right) and blow salt grains off the lakebeds when dry. The bowtie pattern in the upper left has resulted from differing grazing practices among fenced fields.

This cross-eyed stereoscopic image pair was generated using topographic data from the Shuttle Radar Topography Mission, combined with an enhanced Landsat 7satellite color image. The topography data are used to create two differing perspectives of a single image, one perspective for each eye. In doing so, each point in the image is shifted slightly, depending on its elevation. When stereoscopically merged, the result is a vertically exaggerated view of the Earth's surface in its full three dimensions.

Landsat satellites have provided visible light and infrared images of the Earth continuously since 1972. SRTM topographic data match the 30-meter (99-foot) spatial resolution of most Landsat images and provide a valuable complement for studying the historic and growing Landsat data archive. The Landsat 7 Thematic Mapper image used here was provided to the SRTM project by the United States Geological Survey, Earth Resources Observation Systems (EROS) Data Center,Sioux Falls, South Dakota.

Elevation data used in this image was acquired by the Shuttle Radar Topography Mission (SRTM) aboard the Space Shuttle Endeavour, launched on February 11,2000. SRTM used the same radar instrument that comprised the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR) that flew twice on the Space Shuttle Endeavour in 1994. SRTM was designed to collect three-dimensional measurements of the Earth's surface. To collect the 3-D data, engineers added a 60-meter-long (200-foot) mast, installed additional C-band and X-band antennas, and improved tracking and navigation devices. The mission is a cooperative project between the National Aeronautics and Space Administration (NASA), the National Imagery and Mapping Agency (NIMA) of the U.S. Department of Defense (DoD), and the German and Italian space agencies. It is managed by NASA's Jet Propulsion Laboratory, Pasadena, CA, for NASA's Earth Science Enterprise,Washington, DC.

Size: 21.5 kilometers (13.4 miles) x 27.2 kilometers (16.9 miles) Location: 41.6 deg. South lat., 67.9 deg. West lon. Orientation: North toward upper left Image Data: Landsat bands 1,4,7 in blue, green, red Date Acquired: February 19, 2000 (SRTM), January 22, 2000 (Landsat)

2000-01-01

256

Ocean Surface Topography from Space  

NSDL National Science Digital Library

Interactive Flash Module about Ocean Surface Topography. Module includes sea surface observations and measurements as well as visuals explanations of the alimetry instruments used to detect surface changes.

Jet Propulsion Laboratory, California Institute of Technology, NASA

257

EAARL Coastal Topography - Sandy Hook 2007  

USGS Publications Warehouse

These remotely sensed, geographically referenced elevation measurements of Lidar-derived topography were produced as a collaborative effort between the U.S. Geological Survey (USGS), Florida Integrated Science Center (FISC), St. Petersburg, FL; the National Park Service (NPS), Northeast Coastal and Barrier Network, Kingston, RI; and the National Aeronautics and Space Administration (NASA), Wallops Flight Facility, VA. This project provides highly detailed and accurate datasets of Gateway National Recreation Area's Sandy Hook Unit in New Jersey, acquired on May 16, 2007. The datasets are made available for use as a management tool to research scientists and natural resource managers. An innovative airborne Lidar instrument originally developed at the NASA Wallops Flight Facility, and known as the Experimental Advanced Airborne Research Lidar (EAARL) was used during data acquisition. The EAARL system is a raster-scanning, waveform-resolving, green-wavelength (532-nanometer) Lidar designed to map near-shore bathymetry, topography, and vegetation structure simultaneously. The EAARL sensor suite includes the raster-scanning, water-penetrating full-waveform adaptive Lidar, a down-looking red-green-blue (RGB) digital camera, a high-resolution multi-spectral color infrared (CIR) camera, two precision dual-frequency kinematic carrier-phase GPS receivers and an integrated miniature digital inertial measurement unit, which provide for submeter georeferencing of each laser sample. The nominal EAARL platform is a twin-engine Cessna 310 aircraft, but the instrument may be deployed on a range of light aircraft. A single pilot, a Lidar operator, and a data analyst constitute the crew for most survey operations. This sensor has the potential to make significant contributions in measuring sub-aerial and submarine coastal topography within cross-environmental surveys. Elevation measurements were collected over the survey area using the EAARL system, and the resulting data were then processed using the Airborne Lidar Processing System (ALPS), a custom-built processing system developed in a NASA-USGS collaboration. ALPS supports the exploration and processing of Lidar data in an interactive or batch mode. Modules for pre-survey flight line definition, flight path plotting, Lidar raster and waveform investigation, and digital camera image playback have been developed. Processing algorithms have been developed to extract the range to the first and last significant return within each waveform. ALPS is routinely used to create maps that represent submerged or first surface topography. Specialized filtering algorithms have been implemented to determine the 'bare earth' under vegetation from a point cloud of last return elevations.

Nayegandhi, Amar; Brock, John C.; Wright, C. Wayne; Stevens, Sara; Yates, Xan; Bonisteel, Jamie M.

2008-01-01

258

Mercury and Vesta - Preliminary shape and topography  

NASA Astrophysics Data System (ADS)

This year two spacecraft, MESSENGER and Dawn, were placed into orbit around Mercury and the asteroid Vesta, respectively. We have been using stereophotoclinometry (SPC) to analyze MESSENGER and Dawn images both for navigation and to determine the precise shapes and topography of these bodies. Because SPC requires images at different local Sun elevations and azimuths to distinguish between albedo and topographic variations, Mercury presents the challenges of a slow spin rate and a long solar day. Vesta, on the other hand, rotates more than four times per Earth day, allowing a given area of surface to be viewed under rapidly changing illumination and topographic information to be built up rapidly. The essence of SPC is that small pieces of surface called maplets and modeled with digital elevation and albedo are illuminated and correlated with images. Hundreds of these maplets are found in each image, providing a valuable data type for spacecraft navigation. Hundreds of images go into the construction of each maplet, and the resulting multi-image stereo over a wide range of viewing conditions provides a precise determination of the maplet's body-fixed position. The construction of topography with SPC uses each pixel, allowing resolutions comparable to the images themselves. Mercury's topography varies by about 5 km above and below that of a sphere of radius 2440 km. We compare the SPC-derived shape and topography with data from MESSENGER's Mercury Laser Altimeter (MLA). Vesta, although a tenth of Mercury's size, exhibits variations in elevation between 17 km below and 12 km above the equipotential that best matches its surface. The lowest areas lie on the floor of the south polar impact crater, and the highest points lie on the crater's rim.

Gaskell, R. W.; Palmer, E. E.; Mastrodemos, N.; Barnouin, O. S.; Jorda, L.; Taylor, A. H.

2011-12-01

259

ATM Coastal Topography-Alabama 2001  

USGS Publications Warehouse

These remotely sensed, geographically referenced elevation measurements of Lidar-derived first surface (FS) topography were produced collaboratively by the U.S. Geological Survey (USGS), Florida Integrated Science Center (FISC), St. Petersburg, FL, and the National Aeronautics and Space Administration (NASA), Wallops Flight Facility, VA. This project provides highly detailed and accurate datasets of the Alabama coastline, acquired October 3-4, 2001. The datasets are made available for use as a management tool to research scientists and natural resource managers. An innovative scanning Lidar instrument originally developed by NASA, and known as the Airborne Topographic Mapper (ATM), was used during data acquisition. The ATM system is a scanning Lidar system that measures high-resolution topography of the land surface, and incorporates a green-wavelength laser operating at pulse rates of 2 to 10 kilohertz. Measurements from the laser ranging device are coupled with data acquired from inertial navigation system (INS) attitude sensors and differentially corrected global positioning system (GPS) receivers to measure topography of the surface at accuracies of +/-15 centimeters. The nominal ATM platform is a Twin Otter or P-3 Orion aircraft, but the instrument may be deployed on a range of light aircraft. Elevation measurements were collected over the survey area using the ATM system, and the resulting data were then processed using the Airborne Lidar Processing System (ALPS), a custom-built processing system developed in a NASA-USGS collaboration. ALPS supports the exploration and processing of Lidar data in an interactive or batch mode. Modules for pre-survey flight line definition, flight path plotting, Lidar raster and waveform investigation, and digital camera image playback have been developed. Processing algorithms have been developed to extract the range to the first and last significant return within each waveform. ALPS is routinely used to create maps that represent submerged or first surface topography.

Nayegandhi, Amar; Yates, Xan; Brock, John C.; Sallenger, A.H.; Bonisteel, Jamie M.; Klipp, Emily S.; Wright, C. Wayne

2009-01-01

260

ATM Coastal Topography-Mississippi, 2001  

USGS Publications Warehouse

These remotely sensed, geographically referenced elevation measurements of lidar-derived first-surface (FS) topography were produced collaboratively by the U.S. Geological Survey (USGS), Florida Integrated Science Center (FISC), St. Petersburg, FL, and the National Aeronautics and Space Administration (NASA), Wallops Flight Facility, VA. This project provides highly detailed and accurate datasets of the Mississippi coastline, from Lakeshore to Petit Bois Island, acquired September 9-10, 2001. The datasets are made available for use as a management tool to research scientists and natural-resource managers. An innovative scanning lidar instrument originally developed by NASA, and known as the Airborne Topographic Mapper (ATM), was used during data acquisition. The ATM system is a scanning lidar system that measures high-resolution topography of the land surface and incorporates a green-wavelength laser operating at pulse rates of 2 to 10 kilohertz. Measurements from the laser-ranging device are coupled with data acquired from inertial navigation system (INS) attitude sensors and differentially corrected global positioning system (GPS) receivers to measure topography of the surface at accuracies of +/-15 centimeters. The nominal ATM platform is a Twin Otter or P-3 Orion aircraft, but the instrument may be deployed on a range of light aircraft. Elevation measurements were collected over the survey area using the ATM system, and the resulting data were then processed using the Airborne Lidar Processing System (ALPS), a custom-built processing system developed in a NASA-USGS collaboration. ALPS supports the exploration and processing of lidar data in an interactive or batch mode. Modules for presurvey flight-line definition, flight-path plotting, lidar raster and waveform investigation, and digital camera image playback have been developed. Processing algorithms have been developed to extract the range to the first and last significant return within each waveform. ALPS is used routinely to create maps that represent submerged or first-surface topography.

Nayegandhi, Amar; Yates, Xan; Brock, John C.; Sallenger, A.H.; Klipp, Emily S.; Wright, C. Wayne

2009-01-01

261

Radar Astronomy.  

National Technical Information Service (NTIS)

A general review of radar astronomy is given. Typical radar systems are described and results cited. Methods of determining elements of orbits and rotation rates of planets are discussed. A proposed test of the Einstein theory of general relativity is des...

G. H. Pettengill I. I. Shapiro

1965-01-01

262

Radar astronomy  

Microsoft Academic Search

Radar Astronomy is a new and growing branch of Astronomy. Although it seems that radio echo studies must be confined to the solar system, they can play an important part in developing our understanding of the Sun and the planets. At the present time these objects are barely detectable by radar techniques and much of the work has been concerned

J. V. Evans

1960-01-01

263

Radar Sounding of Fast-Flowing Glaciers  

NASA Astrophysics Data System (ADS)

A major challenge in radio glaciology is sounding of fast-flowing glaciers such as Jakobshavn, Helheim, and Kangardlussuq in Greenland. Weak ice-bed echoes from fast-flowing glaciers are masked by off-vertical surface clutter. We need fine resolution both in the along-track and cross-track directions to reduce surface clutter. Synthetic Aperture Radar (SAR) techniques can be used to improve resolution in the along-track direction. However, SAR technique is not useful to synthesize a long-aperture in the cross-track direction unless data can be collected over a grid with a line spacing of about 1 m at 150 MHz. This is impossible to do with an airborne radar. We developed a high-sensitivity radar with array-processing capability in the cross-track direction to reduce clutter. The radar is designed to measure signals as low as 2 nV with a loop sensitivity of about 215 dB with peak power of about 800 W. We have successfully used this radar to obtain ice thickness and bed topography of three outlet glaciers. The radar soundings over Jakobshavn reveal a complex topography with a thickness of about 800 m at calving front and increasing to 2.7 km at about 40 km from the front. In this paper we will provide a brief review of the system that allowed first successful radar soundings of several fast-flowing glaciers, show sample results, and bed topography of a few glaciers.

Gogineni, S.; Leuschen, C.; Li, J.; Smith, L.; Plummer, J.; Hoch, A.

2008-12-01

264

The Global Multi-Resolution Topography (GMRT) Synthesis  

NASA Astrophysics Data System (ADS)

Topographic maps provide a backdrop for research in nearly every earth science discipline. There is particular demand for bathymetry data in the ocean basins, where existing coverage is sparse. Ships and submersibles worldwide are rapidly acquiring large volumes of new data with modern swath mapping systems. The science community is best served by a global topography compilation that is easily accessible, up-to-date, and delivers data in the highest possible (i.e. native) resolution. To meet this need, the NSF-supported Marine Geoscience Data System (MGDS; www.marine-geo.org) has partnered with the National Geophysical Data Center (NGDC; www.ngdc.noaa.gov) to produce the Global Multi-Resolution Topography (GMRT) synthesis - a continuously updated digital elevation model that is accessible through Open Geospatial Consortium (OGC; www.opengeospatial.org) Web services. GMRT had its genesis in 1992 with the NSF RIDGE Multibeam Synthesis (RMBS); later grew to include the Antarctic Multibeam Synthesis (AMBS); expanded again to include the NSF Ridge 2000 and MARGINS programs; and finally emerged as a global compilation in 2005 with the NSF Legacy of Ocean Exploration (LOE) project. The LOE project forged a permanent partnership between MGDS and NGDC, in which swath bathymetry data sets are routinely published and exchanged via the Open Archives Initiative Protocol for Metadata Harvesting (OAI-PMH; www.openarchives.org). GMRT includes both color-shaded relief images and underlying elevation values at ten different resolutions as high as 100m. New data are edited, gridded, and tiled using tools originally developed by William Haxby at Lamont-Doherty Earth Observatory. Global and regional data sources include the NASA Shuttle Radar Topography Mission (SRTM; http://www.jpl.nasa.gov/srtm/); Smith & Sandwell Satellite Predicted Bathymetry (http://topex.ucsd.edu/marine_topo/); SCAR Subglacial Topographic Model of the Antarctic (BEDMAP; http://www.antarctica.ac.uk/bedmap/); and International Bathymetric Chart of the Arctic Ocean (IBCAO; http://www.ngdc.noaa.gov/mgg/bathymetry/arctic/). Local data sources include high-resolution bathymetry swaths and grids from over 210 research cruises, submersible dives, and related compilations to date. GMRT is accessible via a OGC Web Map Service (WMS) which offers dynamic resolution and on-the-fly map re- projection. A growing number of commercial and open-source clients support OGC protocols, including recent versions of Google Earth and Google Maps which now support WMS natively. GMRT is incorporated as a primary basemap in science Web portals and geobrowsers including EarthChem (www.earthchem.org) and GeoMapApp (www.geomapapp.org), which also serves the underlying elevation values. Future development work will include extension of GMRT to higher resolutions; addition of the International Bathymetric Chart of the Southern Ocean (IBCSO; www.ibcso.org) and the improved SRTM V2; and deployment of new OGC services including a Web Coverage Service (WCS) and Web Terrain Service (WTS).

Arko, R.; Ryan, W.; Carbotte, S.; Melkonian, A.; Coplan, J.; O'Hara, S.; Chayes, D.; Weissel, R.; Goodwillie, A.; Ferrini, V.; Stroker, K.; Virden, W.

2007-12-01

265

Visualization of planetary subsurface radar sounder data in three dimensions using stereoscopy  

NASA Astrophysics Data System (ADS)

Planetary subsurface sounding radar data extend the knowledge of planetary surfaces to a third dimension: the depth. The interpretation of delays of radar echoes converted into depth often requires the comparative analysis with other data, mainly topography, and radar data from different orbits can be used to investigate the spatial continuity of signals from subsurface geologic features. This scenario requires taking into account spatially referred information in three dimensions. Three dimensional objects are generally easier to understand if represented into a three dimensional space, and this representation can be improved by stereoscopic vision. Since its invention in the first half of 19th century, stereoscopy has been used in a broad range of application, including scientific visualization. The quick improvement of computer graphics and the spread of graphic rendering hardware allow to apply the basic principles of stereoscopy in the digital domain, allowing the stereoscopic projection of complex models. Specialized system for stereoscopic view of scientific data have been available in the industry, and proprietary solutions were affordable only to large research institutions. In the last decade, thanks to the GeoWall Consortium, the basics of stereoscopy have been applied for setting up stereoscopic viewers based on off-the shelf hardware products. Geowalls have been spread and are now used by several geo-science research institutes and universities. We are exploring techniques for visualizing planetary subsurface sounding radar data in three dimensions and we are developing a hardware system for rendering it in a stereoscopic vision system. Several Free Open Source Software tools and libraries are being used, as their level of interoperability is typically high and their licensing system offers the opportunity to implement quickly new functionalities to solve specific needs during the progress of the project. Visualization of planetary radar data in three dimensions represents a challenging task, and the exploration of different strategies will bring to the selection of the most appropriate ones for a meaningful extraction of information from the products of these innovative instruments.

Frigeri, A.; Federico, C.; Pauselli, C.; Ercoli, M.; Coradini, A.; Orosei, R.

2010-12-01

266

Abyss-Lite: improved bathymetry from a dedicated small satellite delay-Doppler radar altimeter  

Microsoft Academic Search

We describe the rationale, scientific basis, and implementation of a mission to map the ocean's bottom topography with a spatial resolution of 6 km based on a high-precision radar altimeter on a dedicated free-flying spacecraft.

R. K. Raney; W. H. F. Smith; D. T. Sandwell; J. R. Jensen; D. L. Porter; E. Reynolds

2003-01-01

267

Analysis of Low Probability of Intercept (LPI) Radar Signals Using Cyclostationary Processing.  

National Technical Information Service (NTIS)

LPI radar is a class of radar systems that possess certain performance characteristics that make them nearly undetectable by today's digital intercept receivers, This presents a significant tactical problem in the battle space To detect these types of rad...

A. F. Lime

2002-01-01

268

Bistatic SAR coherence over non-planar topographies  

NASA Astrophysics Data System (ADS)

Monostatic Synthetic Aperture Radar (SAR) Coherent Change Detection (CCD) has been found to be of great utility in detecting changes that occur on the ground. Detectable changes of interest include vehicle tracks and water flow. The CCD procedure involves performing repeat pass radar collections, to form a coherence product, where ground disturbances can induce detectable incoherence. However there is usually a difference in the radar collection geometry which can lead to incoherent energy noise entering the CCD, which reduces the detectability of tracks. When sensing flat terrain, the incoherence due to collection geometry difference can be removed through a conventional Fourier image support trimming process. However, it has been found that when the terrain contains non-flat topography, the optimal trimming process is substantially more involved, so much so that a new per-pixel SAR back-projection imaging algorithm has been developed. This algorithm trims off incoherent energy on a per-pixel basis according to the local topography. In order to validate the bistatic SAR generalization to the monostatic per-pixel formalism and algorithm, bistatic change detection measurements were conducted with the GB-SAR system, and these are reported here.

Andre, Daniel B.; Morrison, Keith

2012-05-01

269

SRTM Anaglyph: Inverted Topography, Patagonia, Argentina  

NASA Technical Reports Server (NTRS)

The Meseta de Somuncura is a broad plateau capped by basalt. Near its western edge is evidence of multiple volcanic events and a complex erosion history. Most notable are the long, narrow, and winding lava flows that run across most of the right side of the image. These formed from low-viscosity lava that flowed down gullies over fairly flat terrain. Later, erosion of the landscape continued, and the solidified flows were more resistant than the older surrounding rocks. Consequently, the flows became the ridges we see here. This natural process of converting gullies to ridges is called topographic inversion. See image PIA02755 (upper left corner) for a good example of topographic inversion in its earlier stages.

Other features seen here include numerous and varied closed depressions. The regional drainage is not well integrated, but instead the drainage ends up in salty lakes (dark water, some with bright shores). Wind streaks indicate that winds blow toward the east (right) and blow salt grains off the lake beds when dry. The bowtie pattern in the upper left has resulted from differing grazing practices among fenced fields.

This anaglyph was generated by first draping a Landsat Thematic Mapper image over a topographic map from the Shuttle Radar Topography Mission, then producing the two differing perspectives, one for each eye. When viewed through special glasses, the result is a vertically exaggerated view of the Earth's surface in its full three dimensions. Anaglyph glasses cover the left eye with a red filter and the right eye with a blue filter.

Landsat satellites have provided visible light and infrared images of the Earth continuously since 1972. SRTM topographic data match the 30-meter (99-foot) spatial resolution of most Landsat images and provide a valuable complement for studying the historic and growing Landsat data archive. The Landsat 7 Thematic Mapper image used here was provided to the SRTM project by the United States Geological Survey, Earth Resources Observation Systems (EROS) Data Center,Sioux Falls, South Dakota.

Elevation data used in this image was acquired by the Shuttle Radar Topography Mission (SRTM) aboard the Space Shuttle Endeavour, launched on February 11,2000. SRTM used the same radar instrument that comprised the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR) that flew twice on the Space Shuttle Endeavour in 1994. SRTM was designed to collect three-dimensional measurements of the Earth's surface. To collect the 3-D data, engineers added a 60-meter-long (200-foot) mast, installed additional C-band and X-band antennas, and improved tracking and navigation devices. The mission is a cooperative project between the National Aeronautics and Space Administration (NASA), the National Imagery and Mapping Agency (NIMA) of the U.S. Department of Defense (DoD), and the German and Italian space agencies. It is managed by NASA's Jet Propulsion Laboratory, Pasadena, CA, for NASA's Earth Science Enterprise,Washington, DC.

Size: 21.5 kilometers (13.4 miles) x 27.2 kilometers (16.9 miles) Location: 41.6 deg. South lat., 67.9 deg. West lon. Orientation: North toward upper left Image Data: Landsat band 7 (short infrared) Date Acquired: February 19, 2000 (SRTM), January 22, 2000 (Landsat)

2000-01-01

270

Topography of chance  

NASA Astrophysics Data System (ADS)

We present a model of multiplicative Langevin dynamics that is based on two foundations: the Langevin equation and the notion of multiplicative evolution. The model is a nonlinear mechanism transforming a white-noise input to a dynamic-equilibrium output, using a single control: an underlying convex U-shaped potential function. The output is quantified by a stationary density which can attain a given number of shapes and a given number of randomness categories. The model generates each admissible combination of the output's shape and randomness in a universal and robust fashion. Moreover, practically all the probability distributions that are supported on the positive half-line, and that are commonly encountered and applied across the sciences, can be reverse engineered by this model. Hence, this model is a universal equilibrium mechanism, in the context of multiplicative dynamics, for the robust generation of “chance”: the model's output. In turn, the properties of the produced “chance,” the output's shape and randomness, are determined with mathematical precision by the control's landscape, its topography. Thus, a topographic map of chance is established. As a particular application, probability distributions with power-law tails are shown to be universally and robustly generated by controls on the “edge of convexity”: convex U-shaped potential functions with asymptotically linear wings.

Eliazar, Iddo I.; Cohen, Morrel H.

2013-11-01

271

Density, Isostasy, and Topography  

NSDL National Science Digital Library

Show caption HideA critical component of this activity involves sharing team data with the entire class, done the old-fashioned way on the chalkboard. Details This activity begins with an exploration of a topographic map of the earth, ending with the question: Why is the distribution of topography on the earth bimodal? The students then collect two forms of data. They measure the density of the most common rocks that make up oceanic crust (basalt), continental crust (granite), and the mantle (peridotite). They also measure the density of several different kinds of wood, and how high each kind floats in a tub of water. In each case, they work in teams of two or three and then the entire class shares their data. Based on the data from the wood, they derive an equation that relates the density of the wood to the height at which the block floats in the water - the isostasy equation. They then substitute density values for real rocks into their equation to derive thicknesses for average continental and oceanic crust, and apply their knowledge in order to draw a cross-section of the crust across South America. This activity gives students a real, hands-on and mathematical understanding of the principle of isostasy.

Egger, Anne

272

Void-Filled SRTM Digital Elevation Model of Afghanistan  

USGS Publications Warehouse

EXPLANATION The purpose of this data set is to provide a single consistent elevation model to be used for national scale mapping, GIS, remote sensing applications, and natural resource assessments for Afghanistan's reconstruction. For 11 days in February of 2000, the National Aeronautics and Space Administration (NASA), the National Geospatial-Intelligence Agency ian Space Agency (ASI) flew X-band and C-band radar interferometry onboard the Space Shuttle Endeavor. The mission covered the Earth between 60?N and 57?S and will provide interferometric digital elevation models (DEMs) of approximately 80% of the Earth's land mass when processing is complete. The radar-pointing angle was approximately 55? at scene center. Ascending and descending orbital passes generated multiple interferometric data scenes for nearly all areas. Up to eight passes of data were merged to form the final processed Shuttle Radar Topography Mission (SRTM) DEMs. The effect of merging scenes averages elevation values recorded in coincident scenes and reduces, but does not completely eliminate, the amount of area with layover and terrain shadow effects. The most significant form of data processing for the Afghanistan DEM was gap-filling areas where the SRTM data contained a data void. These void areas are as a result of radar shadow, layover, standing water, and other effects of terrain as well as technical radar interferometry phase unwrapping issues. To fill these gaps, topographic contours were digitized from 1:200,000 - scale Soviet General Staff Topographic Maps which date from the middle to late 1980's. Digital contours were gridded to form elevation models for void areas and subsequently were merged with the SRTM data through GIS and image processing techniques. The data contained in this publication includes SRTM DEM quadrangles projected and clipped in geographic coordinates for the entire country. An index of all available SRTM DEM quadrangles is displayed here: Index_Geo_DD.pdf. Also included are quadrangles projected into their appropriate Universal Transverse Mercator (UTM) projection. The country of Afghanistan spans three UTM Zones: Zone 41, Zone 42, and Zone 43. Maps are stored in their respective UTM Zone projection. Indexes of all available SRTM DEM quadrangles in their respective UTM zone are displayed here: Index_UTM_Z41.pdf, Index_UTM_Z42.pdf, Index_UTM_Z43.pdf.

Chirico, Peter G.; Barrios, Boris

2005-01-01

273

Radar Image, Hokkaido, Japan  

NASA Technical Reports Server (NTRS)

The southeast part of the island of Hokkaido, Japan, is an area dominated by volcanoes and volcanic caldera. The active Usu Volcano is at the lower right edge of the circular Lake Toya-Ko and near the center of the image. The prominent cone above and to the left of the lake is Yotei Volcano with its summit crater. The city of Sapporo lies at the base of the mountains at the top of the image and the town of Yoichi -- the hometown of SRTM astronaut Mamoru Mohri -- is at the upper left edge. The bay of Uchiura-Wan takes up the lower center of the image. In this image, color represents elevation, from blue at the lowest elevations to white at the highest. The radar image has been overlaid to provide more details of the terrain. Due to a processing problem, an island in the center of this crater lake is missing and will be properly placed when further SRTM swaths are processed. The horizontal banding in this image is a processing artifact that will be removed when the navigation information collected by SRTM is fully calibrated. This image was acquired by the Shuttle Radar Topography Mission (SRTM) aboard the Space Shuttle Endeavour, launched on February 11, 2000. SRTM used the same radar instrument that comprised the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR) that flew twice on the Space Shuttle Endeavour in 1994. SRTM was designed to collect three-dimensional measurements of the Earth's surface. To collect the 3-D data, engineers added a 60-meter-long (200-foot) mast, installed additional C-band and X-band antennas, and improved tracking and navigation devices. The mission is a cooperative project between the National Aeronautics and Space Administration (NASA), the National Imagery and Mapping Agency (NIMA) of the U.S. Department of Defense (DoD), and the German and Italian space agencies. It is managed by NASA's Jet Propulsion Laboratory, Pasadena, CA, for NASA's Earth Science Enterprise, Washington, DC. Size: 100 by 150 kilometers (62 by 93 miles) Location: 42.5 deg. North lat., 140.3 deg. East lon. Orientation: North towards upper left Image Data: SRTM Original Data Resolution: SRTM 30 meters (99 feet) Date Acquired: February 17, 2000

2000-01-01

274

Topography of a wrinkled membrane  

NASA Astrophysics Data System (ADS)

Polymerized vesicle membranes on cooling below the transition temperature, undergo a wrinkling transition and resemble a crumpled elastic sheet or a dried prune. We examine the topography of the surface of a wrinkled vesicle using SEM and AFM measurements.

Natrajan, Vinay; Chaieb, Sahraoui

2004-03-01

275

Doppler synthetic aperture radar imaging  

NASA Astrophysics Data System (ADS)

We consider synthetic aperture radar system using ultra-narrowband continuous waveforms, which we refer to as Doppler Synthetic Aperture Radar (DSAR). We present a novel image formation method for bi-static DSAR. Our method first correlates the received signal with a scaled or frequency-shifted version of the transmitted signal over a finite time window, and then uses microlocal analysis to reconstruct the scene by a filtered-backprojection of the correlated signals. Our approach can be used under non-ideal imaging scenarios such as arbitrary flight trajectories and non-flat topography. Furthermore, it is an analytic reconstruction technique which can be made computationally efficient. We present numerical experiments to demonstrate the performance of the proposed method.

Wang, Ling; Yazici, Birsen

2011-05-01

276

FPGA implementation of a software-defined radar processor  

NASA Astrophysics Data System (ADS)

A unified digital pulse compression processor is introduced as a radar-application-specific-processor (RASP) architecture for the next generation of adaptive radar. Based on traditional pulse compression matched filter and correlation receiver, the processor integrates specific designs to handle waveform diversities, which includes random noise waveforms, as well as digital transceiver self-reconfiguration for adaptive radars. Initial prototype of this processor is implemented with the latest Xilinx FPGA device and tested with an RF spaceborne radar transceiver testbed. Initial validation results show the effectiveness of real-time processing and engineering concepts.

Suarez, Hernan; Zhang, Yan Rockee

2013-05-01

277

Terrain Analysis Using Radar Shape-from-Shading  

Microsoft Academic Search

This paper develops a maximum a posteriori (MAP) probability estimation framework for shape-from-shading (SFS) from synthetic aperture radar (SAR) images. The aim is to use this method to reconstruct surface topography from a single radar image of relatively complex terrain. Our MAP framework makes explicit how the recoveryof local surface orientation depends on the whereabouts ofterrainedgefeaturesandtheavailableradarreflectanceinformation.Toapplytheresultingprocesstorealworldradardata,werequire probabilistic models for the

Adrian G. Bors; Edwin R. Hancock; Richard C. Wilson

2003-01-01

278

High-resolution 3D imaging laser radar flight test experiments  

NASA Astrophysics Data System (ADS)

Situation awareness and accurate Target Identification (TID) are critical requirements for successful battle management. Ground vehicles can be detected, tracked, and in some cases imaged using airborne or space-borne microwave radar. Obscurants such as camouflage net and/or tree canopy foliage can degrade the performance of such radars. Foliage can be penetrated with long wavelength microwave radar, but generally at the expense of imaging resolution. The goals of the DARPA Jigsaw program include the development and demonstration of high-resolution 3-D imaging laser radar (ladar) ensor technology and systems that can be used from airborne platforms to image and identify military ground vehicles that may be hiding under camouflage or foliage such as tree canopy. With DARPA support, MIT Lincoln Laboratory has developed a rugged and compact 3-D imaging ladar system that has successfully demonstrated the feasibility and utility of this application. The sensor system has been integrated into a UH-1 helicopter for winter and summer flight campaigns. The sensor operates day or night and produces high-resolution 3-D spatial images using short laser pulses and a focal plane array of Geiger-mode avalanche photo-diode (APD) detectors with independent digital time-of-flight counting circuits at each pixel. The sensor technology includes Lincoln Laboratory developments of the microchip laser and novel focal plane arrays. The microchip laser is a passively Q-switched solid-state frequency-doubled Nd:YAG laser transmitting short laser pulses (300 ps FWHM) at 16 kilohertz pulse rate and at 532 nm wavelength. The single photon detection efficiency has been measured to be > 20 % using these 32x32 Silicon Geiger-mode APDs at room temperature. The APD saturates while providing a gain of typically > 106. The pulse out of the detector is used to stop a 500 MHz digital clock register integrated within the focal-plane array at each pixel. Using the detector in this binary response mode simplifies the signal processing by eliminating the need for analog-to-digital converters and non-linearity corrections. With appropriate optics, the 32x32 array of digital time values represents a 3-D spatial image frame of the scene. Successive image frames illuminated with the multi-kilohertz pulse repetition rate laser are accumulated into range histograms to provide 3-D volume and intensity information. In this article, we describe the Jigsaw program goals, our demonstration sensor system, the data collection campaigns, and show examples of 3-D imaging with foliage and camouflage penetration. Other applications for this 3-D imaging direct-detection ladar technology include robotic vision, avigation of autonomous vehicles, manufacturing quality control, industrial security, and topography.

Marino, Richard M.; Davis, W. R.; Rich, G. C.; McLaughlin, J. L.; Lee, E. I.; Stanley, B. M.; Burnside, J. W.; Rowe, G. S.; Hatch, R. E.; Square, T. E.; Skelly, L. J.; O'Brien, M.; Vasile, A.; Heinrichs, R. M.

2005-05-01

279

Generating nonlinear FM chirp radar signals by multiple integrations  

DOEpatents

A phase component of a nonlinear frequency modulated (NLFM) chirp radar pulse can be produced by performing digital integration operations over a time interval defined by the pulse width. Each digital integration operation includes applying to a respectively corresponding input parameter value a respectively corresponding number of instances of digital integration.

Doerry, Armin W. (Albuquerque, NM) [Albuquerque, NM

2011-02-01

280

Derivation of Digital Elevation Models of Volcanoes Using ASTER  

NASA Astrophysics Data System (ADS)

We are creating digital elevation models (DEMs) of volcanoes using data obtained by the ASTER instrument on the Terra spacecraft. Near infrared data from ASTER can be used to produce DEMs via photogrammetric techniques by virtue of the nadir and aft-looking cameras (providing a fixed base-to-height ratio of 0.6). An automated stereo image auto-correlation technique is used to produce DEMs. To date, we have generated DEMs for Socompa volcano (Chile) and the Koolau/Waianae volcanoes on Oahu (Hawaii). As part of a data validation effort, these topographic data sets are being compared with existing elevation data collected by repeat-pass radar interferometry using ERS-2, and the TOPSAR airborne interferometric radar, respectively. ASTER DEMs appear to be a valuable new data source for volcanological research; Socompa, for instance, experienced a catastrophic landslide several thousand years ago, and we are using the DEM to study the flow characteristics of the landslide. ASTER DEMs appear to be highly complementary to other types of satellite-derived data, such as Shuttle Radar Topography Mission (SRTM) and repeat-pass radar interferometry. ASTER data have several advantages, including low cost (data are free), high spatial resolution (15 m vs. 30 m for ERS-2, or 90 m global coverage for SRTM), good correlation over vegetated areas and high-relief terrain, and the ability to obtain repeat coverage (unlike SRTM). Disadvantages include the potential masking by clouds, low correlation in areas of low relief, and potential low correlation due to atmospheric haze when the instrument is operated in cross-track mode. One of the goals in our work is to better understand potential and limitations of the ASTER DEMs for geomorphic studies of volcanoes.

Garbeil, H.; Mouginis-Mark, P.

2001-05-01

281

Flood delineation from synthetic aperture radar data with the help of a priori knowledge from historical acquisitions and digital elevation models in support of near-real-time flood mapping  

NASA Astrophysics Data System (ADS)

The monitoring of flood events with synthetic aperture radar (SAR) sensors has attracted a considerable amount of attention during the last decade, owing to the growing interest in using spaceborne data in near-real time flood management. Most existing methods for classifying flood extent from SAR data rely on pure image processing techniques. In this paper, we propose a method involving a priori knowledge about an area taken from a multitemporal time series and a digital elevation model. A time series consisting of ENVISAT ASAR acquisitions was geocoded and coregistered. Then, a harmonic model was fitted to each pixel time series. The standardised residuals of the model were classified as flooded when exceeding a certain threshold value. Additionally, the classified flood extent was limited to flood-prone areas which were derived from a freely available DEM using the height above nearest drainage (HAND) index. Comparison with two different reference datasets for two different flood events showed that the approach yielded realistic results but underestimated the inundation extent. Among the possible reasons for this are the rather coarse resolution of 150 m and the sparse data coverage for a substantial part of the time series. Nevertheless, the study shows the potential for production of rapid overviews in near-real time in support of early response to flood crises.

Schlaffer, Stefan; Hollaus, Markus; Wagner, Wolfgang; Matgen, Patrick

2012-10-01

282

Accessibility and Utilization of WSR-88D Radar Precipitation Data for Natural Resource Modeling Applications  

NASA Astrophysics Data System (ADS)

The National Weather Service (NWS) operates approximately 160 WSR-88D radar-precipitation stations as part of a Next Generation Radar (NEXRAD) program that began implementation in 1992. Among other products, these radar sites provide spatial rainfall estimates, at approximately 4 km2 resolution (Stage 1, Level 3 data), with nominal coverage of 96% of the coterminous United States. Effective coverage is much less than this in a given radar domain depending upon storm type and topography. As the original intent of this network was to support operational objectives of the Departments of Defense, Transportation and Commerce, the production of these data have been optimized for detection and mitigation of severe weather events that might result in flooding, destruction of property and loss of life. The primary hydrologic application has been river and flood forecast modeling by 13 NWS River Forecast Centers (RFC). As each RFC is responsible for a large river drainage, data processing and quality control of these data are geared toward optimization over a relatively large spatial domain (>100,000 km2). Use of these data for other hydrologic and natural resource applications is hampered by a lack of tools for data access and manipulation. NWRC has modified decoding and geo-referencing programs to facilitate utilization of these data for other research and management applications. Stage 1, Level 3 Digital Precipitation Array (DPA) files were obtained for the Boise, Idaho radar location (CBX) for the period of January 1998 to December 2000. Nine rain-gauge locations in the Reynolds Creek Experimental Watershed and Snake River Birds of Prey National Conservation Area, south of Boise, were georeferenced relative to the CBX Hydrologic Rainfall Analysis Project (HRAP) grid. NEXRAD estimates of total cumulative rainfall at these sites averaged only 20% of that measured by the local gauge network. This underestimate was attributed in the most part to truncation of low intensity rainfall events by the precipitation detection function (pdf) rather than to mis-calibration of the ZR relationship. At this time, these data are unsuitable as inputs for long-term water balance modeling but may be useful in extreme-event or flood-modeling applications. New tools to extract and manipulate specific subsets of Stage 1, Level 2 radar data may improve our ability to use radar reflectance data for a broader number of applications than are currently supported.

Hardegree, S. P.

2001-12-01

283

Acoustic Radar Employing Particle Velocity Sensors  

Microsoft Academic Search

\\u000a A concept, practical realization and applications of a passive acoustic radar for automatic localization and tracking of sound\\u000a sources were presented in the paper. The device consists of the new kind of multichannel miniature sound intensity sensors\\u000a and a group of digital signal processing algorithms. Contrary to active radars, it does not emit a scanning beam but after\\u000a receiving surroundings

Józef Kotus; Andrzej Czy?ewski

284

Survey of Digital Beam Forming Techniques and Current Technology.  

National Technical Information Service (NTIS)

Digital beamforming provides key advantages over analog beamforming in radar applications where proper response to multiple jammers in a rapidly changing environment is required. Ths survey reviews these advantages and various digital methods for attainin...

J. E. McCord

1988-01-01

285

Geologic interpretation of texture in Seasat and SIR-A radar images  

NASA Technical Reports Server (NTRS)

Geological information in radar images of heavily vegetated areas is contained mainly in the depiction of topography as image texture. This paper describes three techniques for the analysis of texture in radar images: the split-spectrum technique, Fourier transforms of subareas, and spatial frequency bandpass classification. These techniques were applied to a heavily vegetated area of Belize in Central America in order to evaluate their utility for geological mapping; Seasat and Shuttle Imaging Radar (SIR-A) images were considered.

Farr, T. G.

1982-01-01

286

Analysis of synthetic aperture radar imagery  

NASA Technical Reports Server (NTRS)

Some problems faced in applications of radar measurements in hydrology are: (1) adequate calibration of the radar systems and direct digital data will be required in order that repeatable data can be acquired for hydrologic applications; (2) quantitative hydrologic research on a large scale will be prohibitive with aircraft mounted synthetic aperture radar systems due to the system geometry; (3) spacecraft platforms appear to be the best platforms for radar systems when conducting research over watersheds larger than a few square kilometers; (4) experimental radar systems should be designed to avoid use of radomes; and (5) cross polarized X and L band data seem to discriminate between good and poor hydrologic cover better than like polarized data.

Blanchard, B. J.

1977-01-01

287

Progress in mapping bed topography with OIB and other data in Greenland and Antarctica (Invited)  

NASA Astrophysics Data System (ADS)

Bed topography beneath ice sheets is traditionally mapped using radar echo sounding profilers combined with a geostatistical interpolation technique to fill in data gaps and produce an output on a regular grid. Sea floor bathymetry is traditionally mapped with sonar profilers and in more recent years with multibeam sonars, except beneath floating ice shelves. NASA OIB has placed a strong focus on improving the mapping of glacier bed topography and sea floor bathymetry. In Greenland, we will show the current, fundamental limitations of radar echo sounding and the necessity to come up with new approaches. A promising approach is to combine the data with surface ice velocity data and infer ice thickness (and bed topography) on the basis of mass conservation. Examples in Greenland and Antarctica show that the method is robust versus errors from off-nadir returns, surface mass balance, ice thickening, temporal change in velocity and depth-average velocity versus surface velocity. The output products are bed topography maps at 350 m resolution, with 40 m vertical precision, which compare favorably to the best mapping achievable with radar sounding alone. Beneath floating ice shelves, OIB acquired airborne gravity data to infer sea floor bathymetry. Example results in Greenland and Antarctica demonstrate that many of the output products reveal major surprises and the fundamental importance of extending these measurements to other ice shelves and eventually to all floating ice shelves.

Rignot, E. J.; Morlighem, M.; Mouginot, J.; Seroussi, H.; Larour, E. Y.

2013-12-01

288

Highly Integrated Radar Sensor-on-Chip  

NASA Astrophysics Data System (ADS)

A highly integrated 24 GHz radar sensor is presented, based on a Radio Frequency Integrated Circuit (RFIC) which was specifically developed for a Frequency Modulated Shift Keying (FMSK) based Radar system design. Antenna, waveform, the Radio Frequency (RF) and Digital Signal Processor (DSP) module, the software design, cost and performance aspects will be described. The significant technical and economical advantages of the implemented Silicon-Germanium (SiGe) Bipolar CMOS (BiCMOS) transceiver are demonstrated. Some automotive and other applications based on this technology and new radar system design will be explained.

Mende, Ralph

2012-05-01

289

Radar target signature program performance specification  

NASA Astrophysics Data System (ADS)

This report is a Program Performance Specification (PPS) for a digital computer program that calculates the radar signatures of ships. The PPS will be used to guide the program through three development phases and acceptance testing. The primary objectives of the program are accuracy, flexibility of application, ease of modeling, and portability. The ship is modeled by identifying and defining all the geometrical shapes which cause radar scattering and coherently adding the signals from all the appropriate ones. The program will handle far-field, near-field, and bistatic geometries, antenna patterns, radar absorbing material, and high range resolution effects.

Toothman, H. L.

1981-06-01

290

Analysis of synthetic aperture radar imagery  

NASA Technical Reports Server (NTRS)

The author has identified the following significant results. Average radar response for L-band like polarized system appeared to be related to the watershed runoff coefficients when the viewing angle was approximately 42 deg off nadir. Four requirements for radar systems used to verify applications of active microwave for water resources were identified: (1) first generation digital data will be required; (2) radar should be calibrated both internally and externally; (3) new systems should avoid radom use; and (4) images should be geometrically rectified prior to delivery to the user.

Blanchard, B. J. (principal investigator)

1976-01-01

291

Basal topography of Kronebreen, NW Svalbard  

NASA Astrophysics Data System (ADS)

Kronebreen is a tidewater outlet glacier draining the icefield Holtedahlfonna, in the Kongsfjord area of NW Svalbard. Like most glaciers in Svalbard, Kronebreen has been in retreat since the first front positions were recorded, with the exception of a brief advance during the surge of the neighboring glacier Kongsvegen around 1948. Kronebreen is one of the fastest non-surging glaciers in Svalbard, with average annual velocities near the calving front of around 450 m/yr. It has not been possible until recently to calculate ice fluxes, however, since the bottom topography of Kronebreen has been unknown. In 2009, ice thickness data were obtained using low frequency radar from helicopter over the heavily crevassed Kronebreen. These new thickness data are combined with surface elevation maps, older ice depth data, and fjord bathymetry data to create an expanded bed map of the Kongsfjord area. Velocity data of Kronebreen derived from feature tracking of high-res visible imagery is also combined with thickness data to calculate estimates of flux throughout the glacier. Analysis of this new data will give a better understanding of Kronebreen's retreat history, its mass balance and flux into Kongsfjord, and help in making predictions of when and how quickly further glacier retreat may occur.

O'Sadnick, M.; Kohler, J.; Langley, K.; Kehrl, L. M.; Berthier, E.

2010-12-01

292

Simultaneous Topography and Recognition Imaging  

NASA Astrophysics Data System (ADS)

Atomic force microscopy (AFM) has developed into a key technique for the investigation of biological samples. In contrast to other microscopy methods, high lateral resolution down to the nanometer scale and measurements under physiological conditions are possible. Additionally, the piconewton force sensitivity allows accurate data collection for single-molecule interactions. This chapter describes the combination of high-resolution imaging and single-molecule interaction measurements. In the so-called topography and recognition imaging (TREC) mode, the scanning AFM tip is upgraded into a molecular sensor by anchoring a ligand to the tip. Enhanced electronics, including a recently developed feedback loop, allow measurement of the sample topography while simultaneously mapping ligand-binding sites. This results in topography images recorded alongside with recognition images, thereby allowing accurate allocation of the binding sites with a lateral resolution of one to a few nanometers. TREC has been successfully used for recognition imaging on isolated proteins, native and artificial membranes, and cells.

Ebner, A.; Chtcheglova, L. A.; Preiner, J.; Tang, J.; Wildling, L.; Gruber, H. J.; Hinterdorfer, P.

293

Radar Antenna.  

National Technical Information Service (NTIS)

An antenna is described for range-gated, pulse doppler, radar systems. The antenna includes first and second, shortened, half-wave dipoles and first and second reflecting screens. One dipole is fed through a fixed 22 1/2 degree phase-shift network while t...

O. E. Rittenback

1978-01-01

294

Radar Roadmap.  

National Technical Information Service (NTIS)

Instrumentation radar has played a very significant role in testing and training for more than 50 years. Along with optics, it has been a major supplier of time space position information (TSPI). With the advent of the Global Positioning System (GPS), the...

1998-01-01

295

Radar nomenclature  

Microsoft Academic Search

Like much of the equipment used by the armed forces, both civil and military radar systems may be allocated an identification resolved from a synonym, mnemonic, project name, number, application notation, or specialised nomenclature and sometimes may even be based upon the whims of an intelligence reporting service. Of these, mnemonics are very popular; whilst of designation systems used by

J. C. Wise

2004-01-01

296

Mississippi Delta, Radar Image with Colored Height  

NASA Technical Reports Server (NTRS)

[figure removed for brevity, see original site] Click on the image for the animation

About the animation: This simulated view of the potential effects of storm surge flooding on Lake Pontchartrain and the New Orleans area was generated with data from the Shuttle Radar Topography Mission. Although it is protected by levees and sea walls against storm surges of 18 to 20 feet, much of the city is below sea level, and flooding due to storm surges caused by major hurricanes is a concern. The animation shows regions that, if unprotected, would be inundated with water. The animation depicts flooding in one-meter increments.

About the image: The geography of the New Orleans and Mississippi delta region is well shown in this radar image from the Shuttle Radar Topography Mission. In this image, bright areas show regions of high radar reflectivity, such as from urban areas, and elevations have been coded in color using height data also from the mission. Dark green colors indicate low elevations, rising through yellow and tan, to white at the highest elevations.

New Orleans is situated along the southern shore of Lake Pontchartrain, the large, roughly circular lake near the center of the image. The line spanning the lake is the Lake Pontchartrain Causeway, the world's longest over water highway bridge. Major portions of the city of New Orleans are below sea level, and although it is protected by levees and sea walls, flooding during storm surges associated with major hurricanes is a significant concern.

Data used in this image were acquired by the Shuttle Radar Topography Mission aboard the Space Shuttle Endeavour, launched on Feb. 11, 2000. The mission used the same radar instrument that comprised the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar that flew twice on the Space Shuttle Endeavour in 1994. The Shuttle Radar Topography Mission was designed to collect 3-D measurements of the Earth's surface. To collect the 3-D data, engineers added a 60-meter (approximately 200-foot) mast, installed additional C-band and X-band antennas, and improved tracking and navigation devices. The mission is a cooperative project between NASA, the National Geospatial-Intelligence Agency of the U.S. Department of Defense and the German and Italian space agencies. It is managed by NASA's Jet Propulsion Laboratory, Pasadena, Calif., for NASA's Science Mission Directorate, Washington, D.C.

Location: 30 degrees North latitude, 90 degrees East longitude Orientation: North toward the top, Mercator projection Size: 222.6 by 192.8 kilometers (138.3 by 119.8 miles) Image Data: Radar image and colored Shuttle Radar Topography Mission elevation model Date Acquired: February 2000

2005-01-01

297

Topographic Phase Recovery from Stacked ERS Interferometry and a Low-Resolution Digital Elevation Model  

NASA Technical Reports Server (NTRS)

A hybrid approach to topographic recovery from ERS interferometry is developed and assessed. Tropospheric/ionospheric artifacts, imprecise orbital information, and layover are key issues in recovering topography and surface deformation from repeat-pass interferometry. Previously, we developed a phase gradient approach to stacking interferograms to reduce these errors and also to reduce the short-wavelength phase noise (see Sandwell arid Price [1998] and Appendix A). Here the method is extended to use a low-resolution digital elevation model to constrain long-wavelength phase errors and an iteration scheme to minimize errors in the computation of phase gradient. We demonstrate the topographic phase recovery on 16-m postings using 25 ERS synthetic aperture radar images from an area of southern California containing 2700 m of relief. On the basis of a comparison with 81 GPS monuments, the ERS derived topography has a typical absolute accuracy of better than 10 m except in areas of layover. The resulting topographic phase enables accurate two-pass, real-time interferometry even in mountainous areas where traditional phase unwrapping schemes fail. As an example, we form a topography-free (127-m perpendicular baseline) interferogram spanning 7.5 years; fringes from two major earthquakes and a seismic slip on the San Andreas Fault are clearly isolated.

Sandwell, David T.; Sichoix, Lydie; Frey, Herbert V. (Technical Monitor)

2000-01-01

298

Measured and Estimated Seafloor Topography: Land Topography from GTOPO30  

NSDL National Science Digital Library

This web site displays two "clickable" maps - one topographic, and the other a Ship Track Each of 16 regions on the maps displays measured and estimated seafloor topography. A poster of the images can be ordered for a fee. Links to related sites are also provided.

299

FPGA based Ultra-Wideband pseudo-noise radar  

Microsoft Academic Search

A high accuracy experimental platform for Ultra Wide Band (UWB) PN radar performance evaluation has been created. This PN radar platform could be used for the applications such as unmanned- aerial-vehicle anti-collision and short-range distance measurement etc (3). It includes compact size X-band radar transceiver, baseband signal processing in FPGA, high speed analog to digital converter (ADC), and Matlab tools.

Amutha Jayakumar; Asha Durafe

2011-01-01

300

The development of DBF phased array radar system  

Microsoft Academic Search

This paper presents the basic concept and implementation of an 8 element DBF (digital beamforming) phased array radar. The real transmitting patterns with various frequencies, weights and nullings are shown. The receiving pattern is also given

Wang Yan; Wu Manqing; Jin Xueming; Lu Jiaguo

2001-01-01

301

Combined Linear and Nonlinear Radar: Waveform Generation and Capture.  

National Technical Information Service (NTIS)

A combined-radar transceiver is constructed which enables target ranging in both linear and nonlinear (harmonic) receive modes. The transceiver is constructed using an arbitrary waveform generator as the signal source, a high-speed digitizing oscilloscope...

G. J. Mazzaro K. D. Sherbondy

2013-01-01

302

INTEGRATED CONTROL OF COMBINED SEWER REGULATORS USING WEATHER RADAR  

EPA Science Inventory

Integrated operation was simulated of ten dynamic combined sewer regulators on a Montreal interceptor. Detailed review of digital recording weather radar capabilities indicated that it is potentially the best rainfall estimation means for accomplishing the runoff prediction that ...

303

Cave Detection in Limestone using Ground Penetrating Radar  

Microsoft Academic Search

Ground penetrating radar (GPR) is becoming a more common component of the standard array of geophysical techniques that are used by archaeologists. In this paper, we report on the use of GPR to survey an area of archaeologically important karst topography at Kitley Caves in Devon, U.K. We describe the use of GPR to detect voids within a limestone outcrop,

Andrew T. Chamberlain; William Sellers; Chris Proctor; Roslyn Coard

2000-01-01

304

SRAL SAR radar altimeter for sentinel-3 mission  

Microsoft Academic Search

The SRAL SAR radar altimeter is the core instrument of the topography mission carried on board the Sentinel-3 satellite which is planned to be launched in 2012. A detailed overview of this instrument is given in this paper in terms of architecture, functions, modes and performances.

Y. Le Roy; M. Deschaux-Beaume; C. Mavrocordatos; M. Aguirre; F. Heliere

2007-01-01

305

Detection and diagnosis of radar modeling errors using covariance consistency  

Microsoft Academic Search

Often, detection-based tracking algorithms are developed without much regard for the effects of either the radar's analog signal processing or its digital signal-processing algorithms. In this paper, we combine the effects of the radar's signal processing and tracking algorithms to assess the combined effect on covariance consistency of various algorithms. To do this, we first define the terms detection, detection

Andy H. Register; Mahendra Mallik; W. Dale Blair; Chris Burton; Paul Burns

2009-01-01

306

vsb-RADAR - A 35 GHz Doppler Radar For Velocity Distance And Acceleration Measurements On Railbound Vehicles  

Microsoft Academic Search

Certain problems associated with conventional vehicular speed sensing such as wheel slip or wheel lock can be avoided by employing a microwave sensing technique. A 35 GHz doppler-radar has been developed to measure velocity, distance and acceleration of railbound vehicles. This radar, the vsb-RADAR, employs a Gunn-Device, a wave-guide slot antenna and a digital signal processor to provide the measuring

Bertram Keller; Holger Meinel; Bernhard Rembold

1978-01-01

307

Equatorial radar system  

Microsoft Academic Search

A large clear air radar with the sensitivity of an incoherent scatter radar for observing the whole equatorial atmosphere up to 1000 km altitude is now being designed in Japan. The radar, called the Equatorial Radar, will be built in Pontianak, Kalimantan Island, Indonesia (0.03 N, 109.3 E). The system is a 47 MHz monostatic Doppler radar with an active

S. Rukao; T. Tsuda; T. Sato; S. Kato

1989-01-01

308

Radars in space  

NASA Technical Reports Server (NTRS)

The capabilities of active microwave devices operating from space (typically, radar, scatterometers, interferometers, and altimeters) are discussed. General radar parameters and basic radar principles are explained. Applications of these parameters and principles are also explained. Trends in space radar technology, and where space radars and active microwave sensors in orbit are going are discussed.

Delnore, Victor E.

1990-01-01

309

Noninvasive measurement of corneal topography  

Microsoft Academic Search

The authors present a brief overview of the surface to be measured (the cornea of the eye), review the current state of the technology designed to measure the corneal topography, and define the outstanding issues of current significance. The topics discussed include: eye movements; fundamental operating principles of new systems; videokeratographic systems; fundamental limitations of the operating principles; limitations of

R. A. Applegate; H. C. Howland

1995-01-01

310

Reactions of cells to topography  

Microsoft Academic Search

Though contact guidance has been known since the very early days of cell culture very little quantitative examination of the reaction of cells to topography has been made. Exceptions to this subjective approach are given prominence below. Yet if we are to understand how cells react and if we are to be able to design ideal substrata for particular cells

Adam S. G. Curtis; Chris D. W. Wilkinson

1998-01-01

311

A Band FMCW Radar Front-End With Adaptive Leakage Cancellation  

Microsoft Academic Search

Monostatic frequency modulation continuous wave radars that use one antenna to simultaneously transmit and receive can result in compact and lightweight synthetic aperture radar systems. One of the greatest challenges in designing a continuous-wave monostatic radar is realizing enough isolation between the transmitter and the receiver. A novel real-time digital signal processing scheme is proposed to cancel the transmitter leakage

Kaihui Lin; Yuanxun Ethan Wang; Cheng-Keng Pao; Yi-Chi Shih

2006-01-01

312

Imaging a BQM-74E Target Drone Using Coherent Radar Cross Section Measurements  

Microsoft Academic Search

ince the early 1980s and the advent of the modern computer, digital radar imaging has developed into a mature field. In this article, the specific problem of imaging a rotating target with a stationary radar is reviewed and built upon. The relative motion between the rotating target and the stationary radar can be used to create a circular synthetic aperture

Allen J. Bric

1997-01-01

313

Sampling rate influence on detection performance of CFAR algorithms implemented in radar extractor  

Microsoft Academic Search

A radar extractor based on a two-processor digital signal-processing (DSP) card implemented in a standard personal computer (PC) has been developed. A constant false alarm rate (CFAR) processor is applied as a part of radar extractor algorithms. Some particular problems related to the CFAR automatic detection of radar signals are investigated, from theoretical and practical point of view, and given

Miroslav M. Petrovic; Dragan D. Dimitrijevic; Aleksandar T. Kostic

2001-01-01

314

Low-cost radar surveillance of inland waterways for homeland security applications  

Microsoft Academic Search

Low-cost radar systems have been developed for homeland security missions. These detect and track small maneuvering craft in the water. The systems consist of a conventional marine radar, a capture card that digitizes the radar signals, and a computer that processes them. We have an experimental system that can monitor western Lake Ontario. It runs in real time, with operator

P. Weber; A. Premji; T. J. Nohara; C. Krasnor

2004-01-01

315

High Resolution Radar Signal Processor for Isar and Automatic Target Recognition  

Microsoft Academic Search

This paper describes a radar signal processor architecture suitable for implementing monopulse high resolution radar (HRR). A coherent transmitter and receiver radar is used to transmit and process waveforms with long pulse widths and high-bandwidth properties. The received signals are YQ demodulated, sampled and processed using a digital filter matched to the transmitted waveform. The output of the processor is

L. J. Sciaccat; R. J. Evans

1996-01-01

316

Signal Processing for Passive Radar Using OFDM Waveforms  

Microsoft Academic Search

Passive radar is a concept where illuminators of opportunity are used in a multistatic radar setup. New digital signals, like digital audio\\/video broadcast (DAB\\/DVB), are excellent candidates for this scheme, as they are widely available, can be easily decoded to acquire the noise-free signal, and employ orthogonal frequency division multiplex (OFDM). Multicarrier transmission schemes like OFDM use block channel equalization

Christian R. Berger; Bruno Demissie; Jörg Heckenbach; Peter Willett; Shengli Zhou

2010-01-01

317

Radar image processing module development program, phase 3  

NASA Technical Reports Server (NTRS)

The feasibility of using charge coupled devices in an IPM for processing synthetic aperture radar signals onboard the NASA Convair 990 (CV990) aircraft was demonstrated. Radar data onboard the aircraft was recorded and processed using a CCD sampler and digital tape recorder. A description of equipment and testing was provided. The derivation of the digital presum filter was documented. Photographs of the sampler/tape recorder, real time display and circuit boards in the IPM were also included.

1977-01-01

318

Radar echo processing with partitioned de-ramp  

SciTech Connect

The spurious-free dynamic range of a wideband radar system is increased by apportioning de-ramp processing across analog and digital processing domains. A chirp rate offset is applied between the received waveform and the reference waveform that is used for downconversion to the intermediate frequency (IF) range. The chirp rate offset results in a residual chirp in the IF signal prior to digitization. After digitization, the residual IF chirp is removed with digital signal processing.

Dubbert, Dale F.; Tise, Bertice L.

2013-03-19

319

TRMM radar  

NASA Astrophysics Data System (ADS)

The results of a conceptual design study and the performance of key components of the Bread Board Model (BBM) of the Tropical Rainfall Measuring Mission (TRMM) radar are presented. The radar, which operates at 13.8 GHz and is designed to meet TRMM mission objectives, has a minimum measurable rain rate of 0.5 mm/h with a range resolution of 250 m, a horizontal resolution of about 4 km, and a swath width of 220 km. A 128-element active phased array system is adopted to achieve contiguous scanning within the swath. The basic characteristics of BBM were confirmed by experiments. The development of EM started with the cooperation of NASDA and CRL.

Okamoto, Kenichi

1993-05-01

320

TRMM radar  

NASA Technical Reports Server (NTRS)

The results of a conceptual design study and the performance of key components of the Bread Board Model (BBM) of the Tropical Rainfall Measuring Mission (TRMM) radar are presented. The radar, which operates at 13.8 GHz and is designed to meet TRMM mission objectives, has a minimum measurable rain rate of 0.5 mm/h with a range resolution of 250 m, a horizontal resolution of about 4 km, and a swath width of 220 km. A 128-element active phased array system is adopted to achieve contiguous scanning within the swath. The basic characteristics of BBM were confirmed by experiments. The development of EM started with the cooperation of NASDA and CRL.

Okamoto, Kenichi

1993-01-01

321

Radar studies related to the earth resources program. [remote sensing programs  

NASA Technical Reports Server (NTRS)

The radar systems research discussed is directed toward achieving successful application of radar to remote sensing problems in such areas as geology, hydrology, agriculture, geography, forestry, and oceanography. Topics discussed include imaging radar and evaluation of its modification, study of digital processing for synthetic aperture system, digital simulation of synthetic aperture system, averaging techniques studies, ultrasonic modeling of panchromatic system, panchromatic radar/radar spectrometer development, measuring octave-bandwidth response of selected targets, scatterometer system analysis, and a model Fresnel-zone processor for synthetic aperture imagery.

Holtzman, J.

1972-01-01

322

Evaluating soil moisture variability using synthetic aperture radar and terrain indices  

NASA Astrophysics Data System (ADS)

The spatial and temporal variability of soil moisture is influenced by precipitation patterns, local topography, soil texture and vegetation. It is likely that on bare agricultural fields of near homogeneous soil texture, soil moisture distribution is primarily controlled by topography. This research examines the relationship between soil moisture maps derived from satellite-based Synthetic Aperture Radar (SAR) sensors and wetness indices calculated from LiDAR digital elevation models (DEMs) under wet, dry and moderate moisture conditions. The radar response (backscatter) from SAR sensors is related to the dielectric constant of the surface, allowing soil moisture values to be retrieved through inversion techniques in backscatter models. Wetness indices model expected moisture patterns through evaluation of the surface slope and the number of upslope moisture-contributing cells (specific catchment area) at any point. Although multiple wetness indices have been developed and assessed, few researchers have evaluated the relationships of these indices in conjunction with high-resolution SAR imagery. For eight dates spanning fall 2009 and spring 2010, fine quad-polarimetric mode RADARSAT-2 imagery and coincident in situ surface parameter data are used to derive soil moisture maps of a small agricultural watershed in southwestern Ontario. Wetness indices are used as surrogates for soil moisture patterns in the same area. High-resolution LiDAR-derived DEMs at resolutions of 1, 4 and 8 m are used to calculate the ln(As/tan?) wetness index where As is the specific catchment area and ? is the surface slope. Multiple flow accumulation algorithms are employed to define As. Statistical analyses quantify the relationships and the described variance among assorted wetness index outputs and satellite-derived soil moisture under changing surface conditions.

Powell, K. A.; Berg, A. A.

2010-12-01

323

Digital Doppler Processor For Spaceborne Scatterometer  

NASA Technical Reports Server (NTRS)

Report describes conceptual digital Doppler processor for NASA scatterometer (NSCAT), advanced version of SEASAT spaceborne radar scatterometer used to measure winds near surface of ocean. In NSCAT design, six antennas illuminate surface of ocean with fanshaped beams.

LONG. D. G.; Chi, Chong-Yung; Li, Fuk K.

1989-01-01

324

Evolution of Neogene Dynamic Topography in Madagascar  

NASA Astrophysics Data System (ADS)

Madagascar is located on the fringes of the African superswell. Its position and the existence of a +30 mGal long wavelength free-air gravity anomaly suggest that its present-day topography is maintained by convective circulation of the sub-lithospheric mantle. Residual depth anomalies of oceanic crust encompassing the island imply that Madagascar straddles a dynamic topographic gradient. In June-July 2012, we examined geologic evidence for Neogene uplift around the Malagasy coastline. Uplifted coral reef deposits, fossil beach rock, and terraces demonstrate that the northern and southern coasts are probably being uplifted at a rate of ~0.2 mm/yr. Rates of uplift clearly vary around the coastline. Inland, extensive peneplains occur at elevations of 1 - 2 km. These peneplains are underlain by 10 - 20 m thick laterite deposits, and there is abundant evidence for rapid erosion (e.g. lavaka). Basaltic volcanism also occurred during Neogene times. These field observations can be combined with an analysis of drainage networks to determine the spatial and temporal pattern of convectively driven uplift. ~100 longitudinal river profiles were extracted from a digital elevation model of Madagascar. An inverse model is then used to minimize the misfit between observed and calculated river profiles as a function of uplift rate history. During inversion, the residual misfit decreases from ~20 to ~4. Our results suggest that youthful and rapid uplift of 1-2 km occurred at rates of 0.2-0.4 mm/yr during the last ?15 Myr. The algorithm resolves distinct phases of uplift which generate localized swells of high topography and relief (e.g. the Hauts Plateaux). Our field observations and modeling indicate that the evolution of drainage networks may contain useful information about mantle convective processes.

Paul, J. D.; Roberts, G.; White, N. J.

2012-12-01

325

Radar Studies in the Solar System  

NASA Technical Reports Server (NTRS)

We aid in study of the solar system by means of ground-based radar. We have concentrated on: (1) developing the ephemerides needed to acquire radar data at Arecibo Observatory and (2) analyzing the resultant data to: test fundamental laws of gravitation; determine the size , shape, topography, and spin vectors of the targets; and study the surface properties of these objects, through their scattering law and polarization characteristics. We are engaged in radar observations of asteroids and comets, both as systematically planned targets and as "targets of opportunity." In the course of the program, we have prepared ephemerides for about 80 asteroids and three comets, and the radar observations have been made or attempted at the Arecibo Observatory, in most cases successfully, and in some cases on more than one apparition. The results of these observations have included echo spectra for the targets and, in some cases, delay - Doppler images and measurements of the total round-trip delay to the targets. Perhaps the most dramatic of these results are the images obtained for asteroids (4179) Toutatis and 1989PB (Castalia), which were revealed to be double-lobed objects by the radar images. Besides these direct results, the radar observations have furnished information on the sizes and shapes of the targets through analysis of the Doppler width of the echoes as a function of time, and on the surface properties (such as composition, bulk density, and roughness) through analysis of the reflectivity and of the polarization state of the echoes. We have also refined the orbits of the observed asteroids as a result of the Doppler (and in some cases delay) measurements from the radar observations. Although the orbits of main-belt asteroids accessible to ground-based radar are quite well known from the available optical data, some near-Earth objects have been seen by radar very soon after their optical discovery (for example, 199OMF, just eight days after discovery). In such cases. the radar results ensure that the object in question can be anticipated and identified at the next apparition. We have also participated in radar studies of the terrestrial planets. The results of these studies have included both planetary topography profiles from the analysis of round-trip delays to points along the target Doppler equator and determinations of the target spin state. The latter is of special interest in the case of Venus, which is very close to, but not on, a multi-body spin-orbit resonance such that Venus rotates 12 times for every 8 Earth orbits and 13 Venus orbits. As a result, Venus presents nearly the same face toward Earth at each inferior conjunction. Our latest results confirm that the spin state of Venus is slightly off the resonance. The delay measurements from planetary 2 ranging have also been used in combination with other types of range data in testing general relativity with increasing accuracy. We have also been engaged in radar studies of planetary satellites. Using our ephemerides, Arecibo made radar observations of the Galilean satellites of Jupiter and of Mars' satellite Phobos during the favorable opposition seasons (1988-1992 for Jupiter and 1990 for Mars). An attempt was also made to observe Deimos, but without detecting an echo. In 1997, an attempt was made to observe Saturn's satellite Titan, using the newly upgraded Arecibo radar system for transmitting and the Goldstone radar for receiving, but no echo was detected. The study of satellites by radar is in many ways similar to that of asteroids. The results from these observations have included characterization of the surface properties from the reflectivity and polarization ratio, as well as (in the case of the large satellites of Jupiter) the variation of reflectivity with incidence angle.

Shaprio, Irwin I.

1998-01-01

326

Planetary Radar Studies.  

National Technical Information Service (NTIS)

A catalog of lunar and radar anomalies was generated to provide a base for comparison with Venusian radar signatures. The relationships between lunar radar anomalies and regolith processes were investigated, and a consortium was formed to compare lunar an...

T. W. Thompson J. A. Cutts

1981-01-01

327

X-ray Topography in Protein Crystals  

NASA Astrophysics Data System (ADS)

X-ray topography, especially synchrotron X-ray topography, provides a useful tool for the characterization of protein crystals in order to characterize the defects. We observed clear images of dislocations in hen-egg white lysozyme crystals. In this article we overviewed the research on crystal defects, especially dislocations of protein crystals by synchrotron X-ray topography.

Kojima, Kenichi; Tachibana, Masaru

328

Mars Gravity and Topography Interpretations  

NASA Technical Reports Server (NTRS)

New models of the topography of Mars and its gravity field from the Mars Global Surveyor mission are shedding new light on the structure of the planet and the state of isostatic compensation. Gravity field observations over the flat northern hemisphere plains show a number of anomalies at the 100 to 200 mGal level that have no apparent manifestation in the surface topography. We believe that these anomalies are probably the result of ancient impacts and represent regions of denser material buried beneath the outer depositional crust. Similar anomalies are also found in the region of the north polar ice cap even though a gravity anomaly resulting from the 3 km high icecap has not been uniquely identified. This leads us to speculate that the ice cap is largely compensated and is older than the timescale of isostatic compensation, about 10(exp 15) years.

Zuber, Maria T.; Smith, David E.; Solomon, Sean C.; Phillips, Roger J.

1999-01-01

329

NASA experimental airborne doppler radar and real time processor for wind shear detection  

NASA Technical Reports Server (NTRS)

The topics are presented in viewgraph form and include the following: experimental radar system capabilities; an experimental radar system block diagram; wind shear radar signal and data processor (WRSDP); WRSDP hardware architecture; WRSDP system design goals; DSP software development tools; OS-9 software development tools; WRSDP digital signal processing; WRSDP display operational modes; WRSDP division of functions; structure of WRSDP signal and data processing algorithms; and the wind shear radar flight experiment.

Schaffner, Philip H.; Richards, Mark A.; Jones, William R.; Crittenden, Lucille H.

1992-01-01

330

The SIR-C/X-SAR synthetic aperture radar system  

NASA Technical Reports Server (NTRS)

SIR-C/X-SAR, a three-frequency radar to be flown on the Space Shuttle in September 1993, is described. The SIR-C system is a two-frequency radar operating at 1250 MHz (L-band) and 5300 MHz (C-band), and is designed to get four-polarization radar imagery at multiple surface angles. The X-SAR system is an X-band imaging radar operating at 9600 MHz. The discussion covers the mission concept; system design; hardware; RF electronics; digital electronics; command, timing, and telemetry; and testing.

Jordan, Rolando L.; Huneycutt, Bryan L.; Werner, Marian

1991-01-01

331

Wavelet based hierarchical coding scheme for radar image compression  

NASA Astrophysics Data System (ADS)

This paper presents a wavelet based hierarchical coding scheme for radar image compression. Radar signal is firstly quantized to digital signal, and reorganized as raster-scanned image according to radar's repeated period frequency. After reorganization, the reformed image is decomposed to image blocks with different frequency band by 2-D wavelet transformation, each block is quantized and coded by the Huffman coding scheme. A demonstrating system is developed, showing that under the requirement of real time processing, the compression ratio can be very high, while with no significant loss of target signal in restored radar image.

Sheng, Wen; Jiao, Xiaoli; He, Jifeng

2007-11-01

332

Auxiliary signal processing system for a multiparameter radar  

NASA Technical Reports Server (NTRS)

The design of an auxiliary signal processor for a multiparameter radar is described with emphasis on low cost, quick development, and minimum disruption of radar operations. The processor is based around a low-cost digital signal processor card and personal computer controller. With the use of such a concept, an auxiliary processor was implemented for the NCAR CP-2 radar during a 1991 summer field campaign and allowed measurement of additional polarimetric parameters, namely, the differential phase and the copolar cross correlation. Sample data are presented from both the auxiliary and existing radar signal processors.

Chandrasekar, V.; Gray, G. R.; Caylor, I. J.

1993-01-01

333

Shuttle imaging radar-C science plan  

NASA Technical Reports Server (NTRS)

The Shuttle Imaging Radar-C (SIR-C) mission will yield new and advanced scientific studies of the Earth. SIR-C will be the first instrument to simultaneously acquire images at L-band and C-band with HH, VV, HV, or VH polarizations, as well as images of the phase difference between HH and VV polarizations. These data will be digitally encoded and recorded using onboard high-density digital tape recorders and will later be digitally processed into images using the JPL Advanced Digital SAR Processor. SIR-C geologic studies include cold-region geomorphology, fluvial geomorphology, rock weathering and erosional processes, tectonics and geologic boundaries, geobotany, and radar stereogrammetry. Hydrology investigations cover arid, humid, wetland, snow-covered, and high-latitude regions. Additionally, SIR-C will provide the data to identify and map vegetation types, interpret landscape patterns and processes, assess the biophysical properties of plant canopies, and determine the degree of radar penetration of plant canopies. In oceanography, SIR-C will provide the information necessary to: forecast ocean directional wave spectra; better understand internal wave-current interactions; study the relationship of ocean-bottom features to surface expressions and the correlation of wind signatures to radar backscatter; and detect current-system boundaries, oceanic fronts, and mesoscale eddies. And, as the first spaceborne SAR with multi-frequency, multipolarization imaging capabilities, whole new areas of glaciology will be opened for study when SIR-C is flown in a polar orbit.

1986-01-01

334

Radar target signature program performance specification  

Microsoft Academic Search

This report is a Program Performance Specification (PPS) for a digital computer program that calculates the radar signatures of ships. The PPS will be used to guide the program through three development phases and acceptance testing. The primary objectives of the program are accuracy, flexibility of application, ease of modeling, and portability. The ship is modeled by identifying and defining

H. L. Toothman

1981-01-01

335

Processing for spaceborne synthetic aperture radar imagery  

NASA Technical Reports Server (NTRS)

The data handling and processing in using synthetic aperture radar as a satellite-borne earth resources remote sensor is considered. The discussion covers the nature of the problem, the theory, both conventional and potential advanced processing techniques, and a complete computer simulation. It is shown that digital processing is a real possibility and suggests some future directions for research.

Lybanon, M.

1973-01-01

336

Topography, Cell Response, and Nerve Regeneration  

PubMed Central

In the body, cells encounter a complex milieu of signals, including topographical cues. Imposed topography can affect cells on surfaces by promoting adhesion, spreading, alignment, morphological changes, and changes in gene expression. Neural response to topography is complex, and depends on the dimensions and shapes of physical features. Looking toward repair of nerve injuries, strategies are being explored to engineer guidance conduits with precise surface topographies. How neurons and other cell types sense and interpret topography remains to be fully elucidated. Studies reviewed here include those of topography on cellular organization and function as well as potential cellular mechanisms of response.

Hoffman-Kim, Diane; Mitchel, Jennifer A.; Bellamkonda, Ravi V.

2010-01-01

337

Radar Images of the Kuiper Quadrangle (Mercury) from Goldstone Radar Data  

NASA Technical Reports Server (NTRS)

We have assembled all currently processed radar data from 1989 to 1998 into crude images covering the Kuiper (H6) region on Mercury. The data used were taken to support the ephemeris improvement and gravitational physics programs; however, the resolution is good enough in some cases to make north/south ambiguous images that show some features that can be identified with the Mariner 10 features. Topography profiles along the apparent equator are also available; some of these profiles show ridges and rills as well as crater depths and diameters. The combination of the optical imaging and the radar imaging can be helpful in understanding similar features in radar images of the optically unimaged hemisphere.

Jurgens, R. F.; Rojas, F.; Slade, M. A.; Standish, E. M.; Haldemann, A. F. C.

2000-01-01

338

Equatorial Radar System.  

National Technical Information Service (NTIS)

A large clear air radar with the sensitivity of an incoherent scatter radar for observing the whole equatorial atmosphere up to 1000 km altitude is now being designed in Japan. The radar, called the Equatorial Radar, will be built in Pontianak, Kalimantan...

S. Rukao T. Tsuda T. Sato S. Kato

1989-01-01

339

Wind shear radar simulation  

NASA Technical Reports Server (NTRS)

Viewgraphs used in a presentation on wind shear radar simulation are given. Information on a microburst model of radar reflectivity and wind velocity, radar pulse output, the calculation of radar return, microburst power spectrum, and simulation plans are given. A question and answer session is transcribed.

Britt, Charles L.

1988-01-01

340

Radar cross section  

Microsoft Academic Search

The technological evolution in signal processing that has been made in last decades led to improvements in radar performances. Increasing the radar range by improving its sensitivity has been made by the designers of aircraft and other military systems to try to decrease the radar cross section of these types of equipment. The radar cross section is a matter of

L. Nicolaescu; Teofil Oroian

2001-01-01

341

Digital Optical Circuit Technology  

NASA Technical Reports Server (NTRS)

The Proceedings for the 48th Meeting of the AGARD Avionics Panel contain the 18 papers presented a Technical Evaluation Report, and discussions that followed the presentations of papers. Seven papers were presented in the session devoted to optical bistability. Optical logic was addressed by three papers. The session on sources, modulators and demodulators presented three papers. Five papers were given in the final session on all optical systems. The purpose of this Specialists' Meeting was to present the research and development status of digital optical circuit technology and to examine its relevance in the broad context of digital processing, communication, radar, avionics and flight control systems implementation.

Dove, B. L. (editor)

1985-01-01

342

Urban topography: 3D database construction for propagation modeling in an urban environment  

NASA Astrophysics Data System (ADS)

Construction of digital elevation models (DEMs) for natural earth surfaces have now become common practice. What does one do when the topography is caused by the closely-spaced tall buildings of lower Manhattan, New York City. Although the DEM principles are applicable, special problems were encountered in this very exciting and innovative project, requiring unique solutions, which are all discussed in this article.

Goldsmith, Viktor; Williamson, Doug; Tobar, Juan; Becker, Mark

1998-02-01

343

Space shuttle synthetic aperture radar. [using real time  

NASA Technical Reports Server (NTRS)

Results of a feasibility study to investigate a digital signal processor for real-time operation with a synthetic aperture radar system aboard the space shuttle are presented. Pertinent digital processing theory, a description of the proposed system, and size, weight, power, scheduling, and development estimates are included.

1975-01-01

344

Study of Synthetic Aperture Radar (SAR) imagery characteristics  

NASA Technical Reports Server (NTRS)

Sources of geometric and radiometric fidelity errors in AN/APQ-102A radar imagery are discussed, along with a digital computer program to correct the distortions. The major effort, a computer program which will process digitalized recorded AN/APQ-102A phase histories into imagery, is described. All computer programs are listed.

1975-01-01

345

Foldbelt exploration with synthetic aperture radar (SAR) in Papua New Guinea  

SciTech Connect

Synthetic aperture radar (SAR) is being successfully used within the southern fold and thrust belt of Papua New Guinea to map surface structure and stratigraphy and to help plan a hydrocarbon exploration program. The airborne SAR imagery, along with other surface data, is used as a primary exploration tool because acquisition of acceptable seismic data is extremely costly due to extensive outcrops of Tertiary Darai Limestone which develops rugged karst topography. Most anticlines in the licenses are capped with this deeply karstified limestone. The region is ideally suited to geologic analysis using remote sensing technology. The area is seldom cloud free and is covered with tropical rain forest, and geologic field studies are limited. The widespread karst terrain is exceedingly dangerous, if not impossible, to traverse on the ground. SAR is used to guide ongoing field work, modeling of subsurface structure, and selection of well locations. SAR provides their explorationists with an excellent data base because (1) structure is enhanced with low illumination, (2) resolution is 6 x 12 m, (3) digital reprocessing is possible, (4) clouds are penetrated by the SAR, and (5) the survey was designed for stereoscopic photogeology. Landsat images and vertical aerial photographs complement SAR but provide subdued structural information because of minimal shadowing (due to high sun angles) and the jungle cover. SAR imagery reveals large-scale mass wasting that has led to a reevaluation of previously acquired field data. Lithologies can be recognized by textural and tonal changes on the SAR images despite near-continuous canopy of jungle. Reprocessing and contrast stretching of the digital radar imagery provide additional geologic information.

Ellis, J.M.; Pruett, F.D.

1987-05-01

346

Crop classification with a Landsat/radar sensor combination  

NASA Technical Reports Server (NTRS)

A combined Landsat/radar approach to classification of remotely sensed data, with emphasis on crops, was undertaken. Radar data were obtained by microwave radar spectrometers over fields near Eudora, Kansas and Landsat image data were obtained for the same test site. After Landsat digital images were registered and test-cells extracted, a comparable set of radar image pixels were simulated to match the Landsat pixels. The combined data set is then used for classification, and the results are examined with the best combination of sensor variables identified. Finally, the usefulness of radar in a simulated cloud-cover situation is demonstrated. The major conclusion derived from this study is that the combination of radar/optical sensors is superior to either one alone.

Li, R. Y.; Ulaby, F. T.; Eyton, J. R.

1980-01-01

347

Description and demonstration of the new Middle and Upper atmosphere Radar imaging system: 1-D, 2-D, and 3-D imaging of troposphere and stratosphere  

Microsoft Academic Search

The Middle and Upper atmosphere Radar (MUR) was upgraded in March 2004 for radar imaging capability with 5 frequencies across a 1 MHz bandwidth and 25 digital receivers. Although digitization introduces problems of its own, the uniformity of digitization is a great benefit over the analogue system in place before. This increased reliability will help make the new system an

G. Hassenpflug; M. Yamamoto; H. Luce; S. Fukao

2008-01-01

348

ENDO atmospheric EXO atmospheric radar modeling. Radar cross section modeling, appendix L  

Microsoft Academic Search

This effort is concerned with the development and inplementation of a set of digital computer programs that will augment the RADC digital computer radar simulation model procured under Contract F30602-72-C0393 (01707201). The computer programs shall consist of a sequence of subroutines that correspond to separate functions such as a chaff model, target model, propagation effects, and clutter model. The original

R. J. Hancock; F. H. Cleveland

1976-01-01

349

Design consideration and performance analysis of OCT-based topography  

NASA Astrophysics Data System (ADS)

We report a study on design consideration and performance analysis of OCT-based topography by tracking of maximum intensity at each layer's interface. We demonstrate that, for a given stabilized OCT system, a high precision and accuracy of OCT-based layers and thickness topography in the order of tens nanometer can be achieved by using a technique of maximum amplitude tracking. The submicron precision was obtained by over sampling through the FFT of the acquired spectral fringes but was eventually limited by the system stability. Furthermore, we report characterization of a precision, repeatability, and accuracy of the surfaces, sub-surfaces, and thickness topography using our optimized FD-OCT system. We verified that for a given stability of our OCT system, precision of the detected position of signal's peak of down to 20 nm was obtained. In addition, we quantified the degradation of the precision caused by sensitivity fall-off over depth of FD-OCT. The measured precision is about 20 nm at about 0.1 mm depth, and degrades to about 80 nm at 1 mm depth, a position of about 10 dB sensitivity fall-off. The measured repeatability of thickness measurements over depth was approximately 0.04 micron. Finally, the accuracy of the system was verified by comparing with a digital micrometer gauging.

Meemon, Panomsak; Yao, Jianing; Rolland, Jannick P.

2014-03-01

350

Ocean Surface Topography From Space  

NSDL National Science Digital Library

This site provides information on the many aspects of the study of the sea surface from space. Measuring the ocean surface topography provides information for studying global ocean circulation and the oceans heat budget. Regular scanning of the ocean surface to maintain a database of ocean surface topography can help predict short-term changes in weather and longer-term patterns of climate. Educational materials include a wide variety of games, puzzles, and facts; educational entertainment; on-line resources for educators; information about useful books; and links to lesson plans and classroom activities. There is information on obtaining a variety of visual materials on Oceanography and El Nino in both hardcopy form or PDF files. A class activities area presents plans for classroom activities in Oceans, Climate and Life from the "Visit to an Ocean Planet" CD-ROM in PDF format; shows how an El Nino works using common household items; and describes an El Nino Skit for primary grades. This area also lists on-line resources for educators, information about useful books, and links to lesson plans and classroom activities.

Kawasaki, Kristy

2002-12-13

351

Plasma processing for nanostructured topographies  

NASA Astrophysics Data System (ADS)

Plasma and directed ion interactions with materials have been widely observed to create complex surface patterns on a micro- and nano- scale. Generally, these texturizations are byproducts of another intended application (such as a feature formation on a sputtering target) and patterning is considered inconsequential or even detrimental. This work examined the possibility of using these phenomena as primary methods for producing beneficial topographies. Specifically, investigations focused on the use of helium plasma exposure and directed ion etching to create nanostructured surfaces capable of affecting biological interactions with implanted materials. Orthogonal argon ion etching and low energy helium plasma texturization of titanium were considered for use on orthopedic and dental implants as a means of increasing osteoblast activity and bone attachment; and oblique angle etching was evaluated for its use in creating topographies with cell deterrent or anti-thrombogenic properties. In addition, the helium driven evolution of surface features on 6061 aluminum alloy was characterized with respect to ion energy and substrate temperature. These surfaces were then considered for ice phobic applications.

Riedel, Nicholas Alfred

352

Geostatistical analysis of ground-penetrating radar data: A means of describing spatial variation in the subsurface  

Microsoft Academic Search

We have investigated the use of ground-penetrating radar (GPR) as a means of characterizing the heterogeneity of the subsurface. Radar data were collected at several sites in southwestern British Columbia underlain by glaciodeltaic sediments. A cliff face study was conducted in which geostatistical analysis of a digitized photograph of the face and the radar image of the face showed excellent

Jane Rea; Rosemary Knight

1998-01-01

353

Fifty years of radar  

NASA Astrophysics Data System (ADS)

A development history of radar technology is presented, with attention to the driving of radar system design advances by the emergence of such weapon systems as long range aircraft and cruise missiles in World War II and the range of current applications for state-of-the-art radar techniques. The applications noted encompass over-the-horizon backscatter radars for aircraft detection at 500-1800 nmi ranges, ultralow sidelobe antenna military radars, a long range, frequency scanning three-dimensional S-band radar, a shipborne phased array radar for the collection of exoatmospheric and endoatmospheric data on ballistic missile reentry vehicles, multimission/multimode X-band fighter aircraft radars, and phased array air defense radars.

Skolnik, M. I.

1985-02-01

354

Surface Roughness of the Moon Derived from Multi-frequency Radar Data  

NASA Astrophysics Data System (ADS)

Surface roughness of the Moon provides important information concerning both significant questions about lunar surface processes and engineering constrains for human outposts and rover trafficabillity. Impact-related phenomena change the morphology and roughness of lunar surface, and therefore surface roughness provides clues to the formation and modification mechanisms of impact craters. Since the Apollo era, lunar surface roughness has been studied using different approaches, such as direct estimation from lunar surface digital topographic relief, and indirect analysis of Earth-based radar echo strengths. Submillimeter scale roughness at Apollo landing sites has been studied by computer stereophotogrammetry analysis of Apollo Lunar Surface Closeup Camera (ALSCC) pictures, whereas roughness at meter to kilometer scale has been studied using laser altimeter data from recent missions. Though these studies shown lunar surface roughness is scale dependent that can be described by fractal statistics, roughness at centimeter scale has not been studied yet. In this study, lunar surface roughnesses at centimeter scale are investigated using Earth-based 70 cm Arecibo radar data and miniature synthetic aperture radar (Mini-SAR) data at S- and X-band (with wavelengths 12.6 cm and 4.12 cm). Both observations and theoretical modeling show that radar echo strengths are mostly dominated by scattering from the surface and shallow buried rocks. Given the different penetration depths of radar waves at these frequencies (< 30 m for 70 cm wavelength, < 3 m at S-band, and < 1 m at X-band), radar echo strengths at S- and X-band will yield surface roughness directly, whereas radar echo at 70-cm will give an upper limit of lunar surface roughness. The integral equation method is used to model radar scattering from the rough lunar surface, and dielectric constant of regolith and surface roughness are two dominate factors. The complex dielectric constant of regolith is first estimated globally using the regolith composition and the relation among the dielectric constant, bulk density, and regolith composition. The statistical properties of lunar surface roughness are described by the root mean square (RMS) height and correlation length, which represent the vertical and horizontal scale of the roughness. The correlation length and its scale dependence are studied using the topography data from laser altimeter observations from recent lunar missions. As these two parameters are known, surface roughness (RMS slope) can be estimated by minimizing the difference between the observed and modeled radar echo strength. Surface roughness of several regions over Oceanus Procellarum and southeastern highlands on lunar nearside are studied, and preliminary results show that maira is smoother than highlands at 70 cm scale, whereas the situation turns opposite at 12 and 4 cm scale. Surface roughness of young craters is in general higher than that of maria and highlands, indicating large rock population produced during impacting process.

Fa, W.

2011-12-01

355

Radar Range Sidelobe Reduction Using Adaptive Pulse Compression Technique  

NASA Technical Reports Server (NTRS)

Pulse compression has been widely used in radars so that low-power, long RF pulses can be transmitted, rather than a highpower short pulse. Pulse compression radars offer a number of advantages over high-power short pulsed radars, such as no need of high-power RF circuitry, no need of high-voltage electronics, compact size and light weight, better range resolution, and better reliability. However, range sidelobe associated with pulse compression has prevented the use of this technique on spaceborne radars since surface returns detected by range sidelobes may mask the returns from a nearby weak cloud or precipitation particles. Research on adaptive pulse compression was carried out utilizing a field-programmable gate array (FPGA) waveform generation board and a radar transceiver simulator. The results have shown significant improvements in pulse compression sidelobe performance. Microwave and millimeter-wave radars present many technological challenges for Earth and planetary science applications. The traditional tube-based radars use high-voltage power supply/modulators and high-power RF transmitters; therefore, these radars usually have large size, heavy weight, and reliability issues for space and airborne platforms. Pulse compression technology has provided a path toward meeting many of these radar challenges. Recent advances in digital waveform generation, digital receivers, and solid-state power amplifiers have opened a new era for applying pulse compression to the development of compact and high-performance airborne and spaceborne remote sensing radars. The primary objective of this innovative effort is to develop and test a new pulse compression technique to achieve ultrarange sidelobes so that this technique can be applied to spaceborne, airborne, and ground-based remote sensing radars to meet future science requirements. By using digital waveform generation, digital receiver, and solid-state power amplifier technologies, this improved pulse compression technique could bring significant impact on future radar development. The novel feature of this innovation is the non-linear FM (NLFM) waveform design. The traditional linear FM has the limit (-20 log BT -3 dB) for achieving ultra-low-range sidelobe in pulse compression. For this study, a different combination of 20- or 40-microsecond chirp pulse width and 2- or 4-MHz chirp bandwidth was used. These are typical operational parameters for airborne or spaceborne weather radars. The NLFM waveform design was then implemented on a FPGA board to generate a real chirp signal, which was then sent to the radar transceiver simulator. The final results have shown significant improvement on sidelobe performance compared to that obtained using a traditional linear FM chirp.

Li, Lihua; Coon, Michael; McLinden, Matthew

2013-01-01

356

The PACES digital engagement model  

Microsoft Academic Search

This paper describes the Passive and Active Countermeasures Evaluation Simulation (PACES). PACES is best characterized as an engineering level digital engagement model used to study the effectiveness of electronic countermeasures and aircraft maneuvers against threat radar and missile systems. A typical scenario consists of one or two maneuvering aircraft deploying electronic countermeasures (ECM) against a single threat system. PACES includes

E. L. Gau

1997-01-01

357

Analysis of a digital RF memory in a signal-delay application  

SciTech Connect

Laboratory simulation of the approach of a radar fuze towards a target is an important factor in our ability to accurately measure the radar`s performance. This simulation is achieved, in part, by dynamically delaying and attenuating the radar`s transmitted pulse and sending the result back to the radar`s receiver. Historically, the device used to perform the dynamic delay has been a limiting factor in the evaluation of a radar`s performance and characteristics. A new device has been proposed that appears to have more capability than previous dynamic delay devices. This device is the digital RF memory. This report presents the results of an analysis of a digital RF memory used in a signal-delay application. 2 refs.

Jelinek, D.A.

1992-03-01

358

EAARL Coastal Topography-Pearl River Delta 2008: Bare Earth  

USGS Publications Warehouse

These remotely sensed, geographically referenced elevation measurements of Lidar-derived bare earth (BE) topography were produced as a collaborative effort between the U.S. Geological Survey (USGS), Florida Integrated Science Center (FISC), St. Petersburg, FL; the University of New Orleans (UNO), Pontchartrain Institute for Environmental Sciences (PIES), New Orleans, LA; and the National Aeronautics and Space Administration (NASA), Wallops Flight Facility, VA. This project provides highly detailed and accurate datasets of a portion of the Pearl River Delta in Louisiana and Mississippi, acquired March 9-11, 2008. The datasets are made available for use as a management tool to research scientists and natural resource managers. An innovative airborne Lidar instrument originally developed at the NASA Wallops Flight Facility, and known as the Experimental Advanced Airborne Research Lidar (EAARL), was used during data acquisition. The EAARL system is a raster-scanning, waveform-resolving, green-wavelength (532-nanometer) Lidar designed to map near-shore bathymetry, topography, and vegetation structure simultaneously. The EAARL sensor suite includes the raster-scanning, water-penetrating full-waveform adaptive Lidar, a down-looking red-green-blue (RGB) digital camera, a high-resolution multi-spectral color infrared (CIR) camera, two precision dual-frequency kinematic carrier-phase GPS receivers, and an integrated miniature digital inertial measurement unit, which provide for submeter georeferencing of each laser sample. The nominal EAARL platform is a twin-engine Cessna 310 aircraft, but the instrument may be deployed on a range of light aircraft. A single pilot, a Lidar operator, and a data analyst constitute the crew for most survey operations. This sensor has the potential to make significant contributions in measuring sub-aerial and submarine coastal topography within cross-environmental surveys. Elevation measurements were collected over the survey area using the EAARL system, and the resulting data were then processed using the Airborne Lidar Processing System (ALPS), a custom-built processing system developed in a NASA-USGS collaboration. ALPS supports the exploration and processing of Lidar data in an interactive or batch mode. Modules for presurvey flight line definition, flight path plotting, Lidar raster and waveform investigation, and digital camera image playback have been developed. Processing algorithms have been developed to extract the range to the first and last significant return within each waveform. ALPS is used routinely to create maps that represent submerged or first surface topography. Specialized filtering algorithms have been implemented to determine the 'bare earth' under vegetation from a point cloud of last return elevations.

Nayegandhi, Amar; Brock, John C.; Wright, C. Wayne; Miner, Michael D.; Yates, Xan; Bonisteel, Jamie M.

2009-01-01

359

EAARL Coastal Topography-Chandeleur Islands, Louisiana, 2010: Bare Earth  

USGS Publications Warehouse

These remotely sensed, geographically referenced elevation measurements of lidar-derived bare-earth (BE) and submerged topography datasets were produced collaboratively by the U.S. Geological Survey (USGS), St. Petersburg Coastal and Marine Science Center, St. Petersburg, FL, and the National Aeronautics and Space Administration (NASA), Wallops Flight Facility, VA. This project provides highly detailed and accurate datasets of a portion of the Chandeleur Islands, acquired March 3, 2010. The datasets are made available for use as a management tool to research scientists and natural-resource managers. An innovative airborne lidar instrument originally developed at the NASA Wallops Flight Facility, and known as the Experimental Advanced Airborne Research Lidar (EAARL), was used during data acquisition. The EAARL system is a raster-scanning, waveform-resolving, green-wavelength (532-nanometer) lidar designed to map near-shore bathymetry, topography, and vegetation structure simultaneously. The EAARL sensor suite includes the raster-scanning, water-penetrating full-waveform adaptive lidar, a down-looking red-green-blue (RGB) digital camera, a high-resolution multispectral color-infrared (CIR) camera, two precision dual-frequency kinematic carrier-phase GPS receivers, and an integrated miniature digital inertial measurement unit, which provide for sub-meter georeferencing of each laser sample. The nominal EAARL platform is a twin-engine Cessna 310 aircraft, but the instrument may be deployed on a range of light aircraft. A single pilot, a lidar operator, and a data analyst constitute the crew for most survey operations. This sensor has the potential to make significant contributions in measuring sub-aerial and submarine coastal topography within cross-environmental surveys. Elevation measurements were collected over the survey area using the EAARL system, and the resulting data were then processed using the Airborne Lidar Processing System (ALPS), a custom-built processing system developed in a NASA-USGS collaboration. ALPS supports the exploration and processing of lidar data in an interactive or batch mode. Modules for presurvey flight-line definition, flight-path plotting, lidar raster and waveform investigation, and digital camera image playback have been developed. Processing algorithms have been developed to extract the range to the first and last significant return within each waveform. ALPS is used routinely to create maps that represent submerged or sub-aerial topography. Specialized filtering algorithms have been implemented to determine the 'bare earth' under vegetation from a point cloud of last return elevations. For more information about similar projects, please visit the Decision Support for Coastal Science and Management website.

Nayegandhi, Amar; Bonisteel-Cormier, Jamie M.; Brock, John C.; Sallenger, A.H.; Wright, C. Wayne; Nagle, David B.; Vivekanandan, Saisudha; Yates, Xan; Klipp, Emily S.

2010-01-01

360

EAARL Coastal Topography - Northeast Barrier Islands 2007: Bare Earth  

USGS Publications Warehouse

These remotely sensed, geographically referenced elevation measurements of Lidar-derived bare earth (BE) topography were produced collaboratively by the U.S. Geological Survey (USGS), Florida Integrated Science Center (FISC), St. Petersburg, FL, and the National Aeronautics and Space Administration (NASA), Wallops Flight Facility, VA. This project provides highly detailed and accurate datasets of the northeast coastal barrier islands in New York and New Jersey, acquired April 29-30 and May 15-16, 2007. The datasets are made available for use as a management tool to research scientists and natural resource managers. An innovative airborne Lidar instrument originally developed at the NASA Wallops Flight Facility, and known as the Experimental Advanced Airborne Research Lidar (EAARL), was used during data acquisition. The EAARL system is a raster-scanning, waveform-resolving, green-wavelength (532-nanometer) Lidar designed to map near-shore bathymetry, topography, and vegetation structure simultaneously. The EAARL sensor suite includes the raster-scanning, water-penetrating full-waveform adaptive Lidar, a down-looking red-green-blue (RGB) digital camera, a high-resolution multi-spectral color infrared (CIR) camera, two precision dual-frequency kinematic carrier-phase GPS receivers and an integrated miniature digital inertial measurement unit, which provide for submeter georeferencing of each laser sample. The nominal EAARL platform is a twin-engine Cessna 310 aircraft, but the instrument may be deployed on a range of light aircraft. A single pilot, a Lidar operator, and a data analyst constitute the crew for most survey operations. This sensor has the potential to make significant contributions in measuring sub-aerial and submarine coastal topography within cross-environmental surveys. Elevation measurements were collected over the survey area using the EAARL system, and the resulting data were then processed using the Airborne Lidar Processing System (ALPS), a custom-built processing system developed in a NASA-USGS collaboration. ALPS supports the exploration and processing of Lidar data in an interactive or batch mode. Modules for presurvey flight line definition, flight path plotting, Lidar raster and waveform investigation, and digital camera image playback have been developed. Processing algorithms have been developed to extract the range to the first and last significant return within each waveform. ALPS is routinely used to create maps that represent submerged or first surface topography. Specialized filtering algorithms have been implemented to determine the 'bare earth' under vegetation from a point cloud of last return elevations.

Nayegandhi, Amar; Brock, John C.; Sallenger, A. H.; Wright, C. Wayne; Yates, Xan; Bonisteel, Jamie M.

2008-01-01

361

EAARL Coastal Topography - Northern Gulf of Mexico, 2007: Bare Earth  

USGS Publications Warehouse

These remotely sensed, geographically referenced elevation measurements of Lidar-derived bare earth (BE) topography were produced as a collaborative effort between the U.S. Geological Survey (USGS), Florida Integrated Science Center (FISC), St. Petersburg, FL; the National Park Service (NPS), Gulf Coast Network, Lafayette, LA; and the National Aeronautics and Space Administration (NASA), Wallops Flight Facility, VA. The purpose of this project is to provide highly detailed and accurate datasets of select barrier islands and peninsular regions of Louisiana, Mississippi, Alabama, and Florida, acquired on June 27-30, 2007. The datasets are made available for use as a management tool to research scientists and natural resource managers. An innovative airborne Lidar instrument originally developed at the NASA Wallops Flight Facility, and known as the Experimental Advanced Airborne Research Lidar (EAARL), was used during data acquisition. The EAARL system is a raster-scanning, waveform-resolving, green-wavelength (532-nanometer) Lidar designed to map near-shore bathymetry, topography, and vegetation structure simultaneously. The EAARL sensor suite includes the raster-scanning, water-penetrating full-waveform adaptive Lidar, a down-looking red-green-blue (RGB) digital camera, a high-resolution multi-spectral color infrared (CIR) camera, two precision dual-frequency kinematic carrier-phase GPS receivers, and an integrated miniature digital inertial measurement unit which provide for submeter georeferencing of each laser sample. The nominal EAARL platform is a twin-engine Cessna 310 aircraft, but the instrument may be deployed on a range of light aircraft. A single pilot, a Lidar operator, and a data analyst constitute the crew for most survey operations. This sensor has the potential to make significant contributions in measuring sub-aerial and submarine coastal topography within cross-environmental surveys. Elevation measurements were collected over the survey area using the EAARL system and the resulting data were then processed using the Airborne Lidar Processing System (ALPS), a custom-built processing system developed in a NASA-USGS collaboration. ALPS supports the exploration and processing of Lidar data in an interactive or batch mode. Modules for presurvey flight line definition, flight path plotting, Lidar raster and waveform investigation, and digital camera image playback have been developed. Processing algorithms have been developed to extract the range to the first and last significant return within each waveform. ALPS is used routinely to create maps that represent submerged or sub-aerial topography. Specialized filtering algorithms have been implemented to determine the 'bare earth' under vegetation from a point cloud of last return elevations.

Smith, Kathryn E. L.; Nayegandhi, Amar; Wright, C. Wayne; Bonisteel, Jamie M.; Brock, John C.

2009-01-01

362

EAARL Topography - Natchez Trace Parkway 2007: First Surface  

USGS Publications Warehouse

These remotely sensed, geographically referenced elevation measurements of Lidar-derived first surface (FS) topography were produced as a collaborative effort between the U.S. Geological Survey (USGS), Florida Integrated Science Center (FISC), St. Petersburg, FL; the National Park Service (NPS), Gulf Coast Network, Lafayette, LA; and the National Aeronautics and Space Administration (NASA), Wallops Flight Facility, VA. This project provides highly detailed and accurate datasets of a portion of the Natchez Trace Parkway in Mississippi, acquired on September 14, 2007. The datasets are made available for use as a management tool to research scientists and natural resource managers. An innovative airborne Lidar instrument originally developed at the NASA Wallops Flight Facility, and known as the Experimental Advanced Airborne Research Lidar (EAARL), was used during data acquisition. The EAARL system is a raster-scanning, waveform-resolving, green-wavelength (532-nanometer) Lidar designed to map near-shore bathymetry, topography, and vegetation structure simultaneously. The EAARL sensor suite includes the raster-scanning, water-penetrating full-waveform adaptive Lidar, a down-looking red-green-blue (RGB) digital camera, a high-resolution multi-spectral color infrared (CIR) camera, two precision dual-frequency kinematic carrier-phase GPS receivers, and an integrated miniature digital inertial measurement unit, which provide for submeter georeferencing of each laser sample. The nominal EAARL platform is a twin-engine Cessna 310 aircraft, but the instrument may be deployed on a range of light aircraft. A single pilot, a Lidar operator, and a data analyst constitute the crew for most survey operations. This sensor has the potential to make significant contributions in measuring sub-aerial and submarine coastal topography within cross-environmental surveys. Elevation measurements were collected over the survey area using the EAARL system, and the resulting data were then processed using the Airborne Lidar Processing System (ALPS), a custom-built processing system developed in a NASA-USGS collaboration. ALPS supports the exploration and processing of Lidar data in an interactive or batch mode. Modules for presurvey flight line definition, flight path plotting, Lidar raster and waveform investigation, and digital camera image playback have been developed. Processing algorithms have been developed to extract the range to the first and last significant return within each waveform. ALPS is used routinely to create maps that represent submerged or first surface topography. Specialized filtering algorithms have been implemented to determine the 'bare earth' under vegetation from a point cloud of last return elevations.

Nayegandhi, Amar; Brock, John C.; Wright, C. Wayne; Segura, Martha; Yates, Xan

2008-01-01

363

EAARL Coastal Topography--Cape Canaveral, Florida, 2009: First Surface  

USGS Publications Warehouse

These remotely sensed, geographically referenced elevation measurements of lidar-derived first-surface (FS) topography datasets were produced collaboratively by the U.S. Geological Survey (USGS), St. Petersburg Coastal and Marine Science Center, St. Petersburg, FL, and the National Aeronautics and Space Administration (NASA), Kennedy Space Center, FL. This project provides highly detailed and accurate datasets of a portion of the eastern Florida coastline beachface, acquired on May 28, 2009. The datasets are made available for use as a management tool to research scientists and natural-resource managers. An innovative airborne lidar instrument originally developed at the NASA Wallops Flight Facility, and known as the Experimental Advanced Airborne Research Lidar (EAARL), was used during data acquisition. The EAARL system is a raster-scanning, waveform-resolving, green-wavelength (532-nanometer) lidar designed to map near-shore bathymetry, topography, and vegetation structure simultaneously. The EAARL sensor suite includes the raster-scanning, water-penetrating full-waveform adaptive lidar, a down-looking red-green-blue (RGB) digital camera, a high-resolution multispectral color-infrared (CIR) camera, two precision dual-frequency kinematic carrier-phase GPS receivers, and an integrated miniature digital inertial measurement unit, which provide for sub-meter georeferencing of each laser sample. The nominal EAARL platform is a twin-engine aircraft, but the instrument was deployed on a Pilatus PC-6. A single pilot, a lidar operator, and a data analyst constitute the crew for most survey operations. This sensor has the potential to make significant contributions in measuring sub-aerial and submarine coastal topography within cross-environmental surveys. Elevation measurements were collected over the survey area using the EAARL system, and the resulting data were then processed using the Airborne Lidar Processing System (ALPS), a custom-built processing system developed in a NASA-USGS collaboration. ALPS supports the exploration and processing of lidar data in an interactive or batch mode. Modules for presurvey flight-line definition, flight-path plotting, lidar raster and waveform investigation, and digital camera image playback have been developed. Processing algorithms have been developed to extract the range to the first and last significant return within each waveform. ALPS is used routinely to create maps that represent submerged or sub-aerial topography. Specialized filtering algorithms have been implemented to determine the "bare earth" under vegetation from a point cloud of last return elevations.

Bonisteel-Cormier, J.M.; Nayegandhi, Amar; Plant, Nathaniel; Wright, C.W.; Nagle, D.B.; Serafin, K.S.; Klipp, E.S.

2011-01-01

364

EAARL Coastal Topography-Pearl River Delta 2008: First Surface  

USGS Publications Warehouse

These remotely sensed, geographically referenced elevation measurements of Lidar-derived first surface (FS) topography were produced as a collaborative effort between the U.S. Geological Survey (USGS), Florida Integrated Science Center (FISC), St. Petersburg, FL; the University of New Orleans (UNO), Pontchartrain Institute for Environmental Sciences (PIES), New Orleans, LA; and the National Aeronautics and Space Administration (NASA), Wallops Flight Facility, VA. This project provides highly detailed and accurate datasets of a portion of the Pearl River Delta in Louisiana and Mississippi, acquired March 9-11, 2008. The datasets are made available for use as a management tool to research scientists and natural resource managers. An innovative airborne Lidar instrument originally developed at the NASA Wallops Flight Facility, and known as the Experimental Advanced Airborne Research Lidar (EAARL), was used during data acquisition. The EAARL system is a raster-scanning, waveform-resolving, green-wavelength (532-nanometer) Lidar designed to map near-shore bathymetry, topography, and vegetation structure simultaneously. The EAARL sensor suite includes the raster-scanning, water-penetrating full-waveform adaptive Lidar, a down-looking red-green-blue (RGB) digital camera, a high-resolution multi-spectral color infrared (CIR) camera, two precision dual-frequency kinematic carrier-phase GPS receivers, and an integrated miniature digital inertial measurement unit, which provide for submeter georeferencing of each laser sample. The nominal EAARL platform is a twin-engine Cessna 310 aircraft, but the instrument may be deployed on a range of light aircraft. A single pilot, a Lidar operator, and a data analyst constitute the crew for most survey operations. This sensor has the potential to make significant contributions in measuring sub-aerial and submarine coastal topography within cross-environmental surveys. Elevation measurements were collected over the survey area using the EAARL system, and the resulting data were then processed using the Airborne Lidar Processing System (ALPS), a custom-built processing system developed in a NASA-USGS collaboration. ALPS supports the exploration and processing of Lidar data in an interactive or batch mode. Modules for presurvey flight line definition, flight path plotting, Lidar raster and waveform investigation, and digital camera image playback have been developed. Processing algorithms have been developed to extract the range to the first and last significant return within each waveform. ALPS is used routinely to create maps that represent submerged or first surface topography. Specialized filtering algorithms have been implemented to determine the 'bare earth' under vegetation from a point cloud of last return elevations.

Nayegandhi, Amar; Brock, John C.; Wright, C. Wayne; Miner, Michael D.; Michael D.; Yates, Xan; Bonisteel, Jamie M.

2009-01-01

365

EAARL Coastal Topography - Northeast Barrier Islands 2007: First Surface  

USGS Publications Warehouse

These remotely sensed, geographically referenced elevation measurements of Lidar-derived first surface (FS) topography were produced collaboratively by the U.S. Geological Survey (USGS), Florida Integrated Science Center (FISC), St. Petersburg, FL, and the National Aeronautics and Space Administration (NASA), Wallops Flight Facility, VA. This project provides highly detailed and accurate datasets of the northeast coastal barrier islands in New York and New Jersey, acquired April 29-30 and May 15-16, 2007. The datasets are made available for use as a management tool to research scientists and natural resource managers. An innovative airborne Lidar instrument originally developed at the NASA Wallops Flight Facility, and known as the Experimental Advanced Airborne Research Lidar (EAARL), was used during data acquisition. The EAARL system is a raster-scanning, waveform-resolving, green-wavelength (532-nanometer) Lidar designed to map near-shore bathymetry, topography, and vegetation structure simultaneously. The EAARL sensor suite includes the raster-scanning, water-penetrating full-waveform adaptive Lidar, a down-looking red-green-blue (RGB) digital camera, a high-resolution multi-spectral color infrared (CIR) camera, two precision dual-frequency kinematic carrier-phase GPS receivers, and an integrated miniature digital inertial measurement unit, which provide for submeter georeferencing of each laser sample. The nominal EAARL platform is a twin-engine Cessna 310 aircraft, but the instrument may be deployed on a range of light aircraft. A single pilot, a Lidar operator, and a data analyst constitute the crew for most survey operations. This sensor has the potential to make significant contributions in measuring sub-aerial and submarine coastal topography within cross-environmental surveys. Elevation measurements were collected over the survey area using the EAARL system, and the resulting data were then processed using the Airborne Lidar Processing System (ALPS), a custom-built processing system developed in a NASA-USGS collaboration. ALPS supports the exploration and processing of Lidar data in an interactive or batch mode. Modules for presurvey flight line definition, flight path plotting, Lidar raster and waveform investigation, and digital camera image playback have been developed. Processing algorithms have been developed to extract the range to the first and last significant return within each waveform. ALPS is routinely used to create maps that represent submerged or first surface topography. Specialized filtering algorithms have been implemented to determine the 'bare earth' under vegetation from a point cloud of last return elevations.

Nayegandhi, Amar; Brock, John C.; Sallenger, A. H.; Wright, C. Wayne; Yates, Xan; Bonisteel, Jamie M.

2009-01-01

366

EAARL Topography - Jean Lafitte National Historical Park and Preserve 2006  

USGS Publications Warehouse

These remotely sensed, geographically referenced elevation measurements of Lidar-derived first surface (FS) and bare earth (BE) topography were produced as a collaborative effort between the U.S. Geological Survey (USGS), Florida Integrated Science Center (FISC), St. Petersburg, FL; the National Park Service (NPS), Gulf Coast Network, Lafayette, LA; and the National Aeronautics and Space Administration (NASA), Wallops Flight Facility, VA. This project provides highly detailed and accurate datasets of the Jean Lafitte National Historical Park and Preserve in Louisiana, acquired on September 22, 2006. The datasets are made available for use as a management tool to research scientists and natural resource managers. An innovative airborne Lidar instrument originally developed at the NASA Wallops Flight Facility, and known as the Experimental Advanced Airborne Research Lidar (EAARL), was used during data acquisition. The EAARL system is a raster-scanning, waveform-resolving, green-wavelength (532-nanometer) Lidar designed to map near-shore bathymetry, topography, and vegetation structure simultaneously. The EAARL sensor suite includes the raster-scanning, water-penetrating full-waveform adaptive Lidar, a down-looking red-green-blue (RGB) digital camera, a high-resolution multi-spectral color infrared (CIR) camera, two precision dual-frequency kinematic carrier-phase GPS receivers, and an integrated miniature digital inertial measurement unit, which provide for submeter georeferencing of each laser sample. The nominal EAARL platform is a twin-engine Cessna 310 aircraft, but the instrument may be deployed on a range of light aircraft. A single pilot, a Lidar operator, and a data analyst constitute the crew for most survey operations. This sensor has the potential to make significant contributions in measuring sub-aerial and submarine coastal topography within cross-environmental surveys. Elevation measurements were collected over the survey area using the EAARL system, and the resulting data were then processed using the Airborne Lidar Processing System (ALPS), a custom-built processing system developed in a NASA-USGS collaboration. ALPS supports the exploration and processing of Lidar data in an interactive or batch mode. Modules for presurvey flight line definition, flight path plotting, Lidar raster and waveform investigation, and digital camera image playback have been developed. Processing algorithms have been developed to extract the range to the first and last significant return within each waveform. ALPS is used routinely to create maps that represent submerged or first surface topography. Specialized filtering algorithms have been implemented to determine the 'bare earth' under vegetation from a point cloud of last return elevations.

Nayegandhi, Amar; Brock, John C.; Wright, C. Wayne; Segura, Martha; Yates, Xan

2008-01-01

367

EAARL Coastal Topography - Fire Island National Seashore 2007  

USGS Publications Warehouse

These remotely sensed, geographically referenced elevation measurements of Lidar-derived first surface (FS) and bare earth (BE) topography were produced as a collaborative effort between the U.S. Geological Survey (USGS), Florida Integrated Science Center (FISC), St. Petersburg, FL; the National Park Service (NPS), Northeast Coastal and Barrier Network, Kingston, RI; and the National Aeronautics and Space Administration (NASA), Wallops Flight Facility, VA. This project provides highly detailed and accurate datasets of Fire Island National Seashore in New York, acquired on April 29-30 and May 15-16, 2007. The datasets are made available for use as a management tool to research scientists and natural resource managers. An innovative airborne Lidar instrument originally developed at the NASA Wallops Flight Facility, and known as the Experimental Advanced Airborne Research Lidar (EAARL) was used during data acquisition. The EAARL system is a raster-scanning, waveform-resolving, green-wavelength (532-nanometer) Lidar designed to map near-shore bathymetry, topography, and vegetation structure simultaneously. The EAARL sensor suite includes the raster-scanning, water-penetrating full-waveform adaptive Lidar, a down-looking red-green-blue (RGB) digital camera, a high-resolution multi-spectral color infrared (CIR) camera, two precision dual-frequency kinematic carrier-phase GPS receivers and an integrated miniature digital inertial measurement unit, which provide for submeter georeferencing of each laser sample. The nominal EAARL platform is a twin-engine Cessna 310 aircraft, but the instrument may be deployed on a range of light aircraft. A single pilot, a Lidar operator, and a data analyst constitute the crew for most survey operations. This sensor has the potential to make significant contributions in measuring sub-aerial and submarine coastal topography within cross-environmental surveys. Elevation measurements were collected over the survey area using the EAARL system, and the resulting data were then processed using the Airborne Lidar Processing System (ALPS), a custom-built processing system developed in a NASA-USGS collaboration. ALPS supports the exploration and processing of Lidar data in an interactive or batch mode. Modules for pre-survey flight line definition, flight path plotting, Lidar raster and waveform investigation, and digital camera image playback have been developed. Processing algorithms have been developed to extract the range to the first and last significant return within each waveform. ALPS is routinely used to create maps that represent submerged or first surface topography. Specialized filtering algorithms have been implemented to determine the 'bare earth' under vegetation from a point cloud of last return elevations.

Nayegandhi, Amar; Brock, John C.; Wright, C. Wayne; Stevens, Sara; Yates, Xan; Bonisteel, Jamie M.

2008-01-01

368

EAARL Submerged Topography - U.S. Virgin Islands 2003  

USGS Publications Warehouse

These remotely sensed, geographically referenced elevation measurements of Lidar-derived submerged topography were produced as a collaborative effort between the U.S. Geological Survey (USGS), Florida Integrated Science Center (FISC), St. Petersburg, FL; the National Park Service (NPS), South Florida-Caribbean Network, Miami, FL; and the National Aeronautics and Space Administration (NASA), Wallops Flight Facility, VA. This project provides highly detailed and accurate bathymetric datasets of a portion of the U.S. Virgin Islands, acquired on April 21, 23, and 30, May 2, and June 14 and 17, 2003. The datasets are made available for use as a management tool to research scientists and natural resource managers. An innovative airborne Lidar instrument originally developed at the NASA Wallops Flight Facility, and known as the Experimental Advanced Airborne Research Lidar (EAARL), was used during data acquisition. The EAARL system is a raster-scanning, waveform-resolving, green-wavelength (532-nanometer) Lidar designed to map near-shore bathymetry, topography, and vegetation structure simultaneously. The EAARL sensor suite includes the raster-scanning, water-penetrating full-waveform adaptive Lidar, a down-looking red-green-blue (RGB) digital camera, a high-resolution multi-spectral color infrared (CIR) camera, two precision dual-frequency kinematic carrier-phase GPS receivers, and an integrated miniature digital inertial measurement unit, which provide for submeter georeferencing of each laser sample. The nominal EAARL platform is a twin-engine Cessna 310 aircraft, but the instrument may be deployed on a range of light aircraft. A single pilot, a Lidar operator, and a data analyst constitute the crew for most survey operations. This sensor has the potential to make significant contributions in measuring sub-aerial and submarine coastal topography within cross-environmental surveys. Elevation measurements were collected over the survey area using the EAARL system, and the resulting data were then processed using the Airborne Lidar Processing System (ALPS), a custom-built processing system developed in a NASA-USGS collaboration. ALPS supports the exploration and processing of Lidar data in an interactive or batch mode. Modules for presurvey flight line definition, flight path plotting, Lidar raster and waveform investigation, and digital camera image playback have been developed. Processing algorithms have been developed to extract the range to the first and last significant return within each waveform. ALPS is used routinely to create maps that represent submerged or first surface topography. Specialized filtering algorithms have been implemented to determine the 'bare earth' under vegetation from a point cloud of last return elevations.

Nayegandhi, Amar; Brock, John C.; Wright, C. Wayne; Stevens, Sara; Yates, Xan; Bonisteel, Jamie M.

2008-01-01

369

Calculation and Error Analysis of a Digital Elevation Model of Hofsjokull, Iceland from SAR Interferometry  

NASA Technical Reports Server (NTRS)

Two ascending European Space Agency (ESA) Earth Resources Satellites (ERS)-1/-2 tandem-mode, synthetic aperture radar (SAR) pairs are used to calculate the surface elevation of Hofsjokull, an ice cap in central Iceland. The motion component of the interferometric phase is calculated using the 30 arc-second resolution USGS GTOPO30 global digital elevation product and one of the ERS tandem pairs. The topography is then derived by subtracting the motion component from the other tandem pair. In order to assess the accuracy of the resultant digital elevation model (DEM), a geodetic airborne laser-altimetry swath is compared with the elevations derived from the interferometry. The DEM is also compared with elevations derived from a digitized topographic map of the ice cap from the University of Iceland Science Institute. Results show that low temporal correlation is a significant problem for the application of interferometry to small, low-elevation ice caps, even over a one-day repeat interval, and especially at the higher elevations. Results also show that an uncompensated error in the phase, ramping from northwest to southeast, present after tying the DEM to ground-control points, has resulted in a systematic error across the DEM.

Barton, Jonathan S.; Hall, Dorothy K.; Sigurosson, Oddur; Williams, Richard S., Jr.; Smith, Laurence C.; Garvin, James B.

1999-01-01

370

Noncircular waveforms exploitation for Radar Signal processing: Survey and study for agile radar waveform  

Microsoft Academic Search

With new generation of Active Digital Radar Antenna, there is a renewal of waveform generation and processing approaches, and new strategies can be explored to optimize waveform design and waveform analysis and to benefit of all potential waveform diversity. Among these strategies, building and exploitation of the Noncircularity of waveforms is a promising issue. Up to the middle of the

F. Barbaresco; P. Chevalier

2009-01-01

371

Local topography of Mars and its relationship to surface weathering processes  

NASA Technical Reports Server (NTRS)

There is a growing body of evidence in favor of the importance of aqueous sedimentary processes on Mars. It is important to understand the role that surface weathering processes have played in the development of the present morphology of the Martian surface. Such an understanding is important not only for its relevance to the study of volatile sources and sinks on Mars through time, but also for its relevance to Martian geologic and tectonic history. Starting in the fall of this year, the Mars Observer Laser Altimeter will begin sending back to Earth data on the topography of Mars that is of a higher quality than most of the topography data available for the Earth. This data will be invaluable, not only for understanding global and large-scale regional processes and landforms on Mars, but also for the study of local and smaller-scale regional processes and landforms. Digital topography is an important part of geologic and geomorphic studies, useful in distinguishing between different lithologies and between different types of weathering. Digital topography data may be used to study a wide variety of local and regional-scale landforms, including valleys, sand dunes, lava flows, landslides, and slopes. Topography data are also essential to the analysis of spectral response patterns, especially in areas of high topographic relief. Geomorphic classification can be significantly improved by the addition of topographic information.

Schaefer, M. W.

1993-01-01

372

ATM Coastal Topography-Texas, 2001: UTM Zone 15  

USGS Publications Warehouse

These remotely sensed, geographically referenced elevation measurements of lidar-derived first-surface (FS) topography were produced collaboratively by the U.S. Geological Survey (USGS), Florida Integrated Science Center (FISC), St. Petersburg, FL, and the National Aeronautics and Space Administration (NASA), Wallops Flight Facility, VA. This project provides highly detailed and accurate datasets of a portion of the Texas coastline within UTM zone 15, from Matagorda Peninsula to Galveston Island, acquired October 12-13, 2001. The datasets are made available for use as a management tool to research scientists and natural-resource managers. An innovative scanning lidar instrument originally developed by NASA, and known as the Airborne Topographic Mapper (ATM), was used during data acquisition. The ATM system is a scanning lidar system that measures high-resolution topography of the land surface and incorporates a green-wavelength laser operating at pulse rates of 2 to 10 kilohertz. Measurements from the laser-ranging device are coupled with data acquired from inertial navigation system (INS) attitude sensors and differentially corrected global positioning system (GPS) receivers to measure topography of the surface at accuracies of +/-15 centimeters. The nominal ATM platform is a Twin Otter or P-3 Orion aircraft, but the instrument may be deployed on a range of light aircraft. Elevation measurements were collected over the survey area using the ATM system, and the resulting data were then processed using the Airborne Lidar Processing System (ALPS), a custom-built processing system developed in a NASA-USGS collaboration. ALPS supports the exploration and processing of lidar data in an interactive or batch mode. Modules for presurvey flight-line definition, flight-path plotting, lidar raster and waveform investigation, and digital camera image playback have been developed. Processing algorithms have been developed to extract the range to the first and last significant return within each waveform. ALPS is used routinely to create maps that represent submerged or first-surface topography.

Klipp, Emily S.; Nayegandhi, Amar; Brock, John C.; Sallenger, A.H.; Bonisteel, Jamie M.; Yates, Xan; Wright, C. Wayne

2009-01-01

373

ATM Coastal Topography-Florida 2001: Western Panhandle  

USGS Publications Warehouse

These remotely sensed, geographically referenced elevation measurements of Lidar-derived first surface (FS) topography were produced collaboratively by the U.S. Geological Survey (USGS), Florida Integrated Science Center (FISC), St. Petersburg, FL, and the National Aeronautics and Space Administration (NASA), Wallops Flight Facility, VA. This project provides highly detailed and accurate datasets of the western Florida panhandle coastline, acquired October 2-4 and 7-10, 2001. The datasets are made available for use as a management tool to research scientists and natural resource managers. An innovative scanning Lidar instrument originally developed by NASA, and known as the Airborne Topographic Mapper (ATM), was used during data acquisition. The ATM system is a scanning Lidar system that measures high-resolution topography of the land surface and incorporates a green-wavelength laser operating at pulse rates of 2 to 10 kilohertz. Measurements from the laser-ranging device are coupled with data acquired from inertial navigation system (INS) attitude sensors and differentially corrected global positioning system (GPS) receivers to measure topography of the surface at accuracies of +/-15 centimeters. The nominal ATM platform is a Twin Otter or P-3 Orion aircraft, but the instrument may be deployed on a range of light aircraft. Elevation measurements were collected over the survey area using the ATM system, and the resulting data were then processed using the Airborne Lidar Processing System (ALPS), a custom-built processing system developed in a NASA-USGS collaboration. ALPS supports the exploration and processing of Lidar data in an interactive or batch mode. Modules for presurvey flight line definition, flight path plotting, Lidar raster and waveform investigation, and digital camera image playback have been developed. Processing algorithms have been developed to extract the range to the first and last significant return within each waveform. ALPS is routinely used to create maps that represent submerged or first surface topography.

Yates, Xan; Nayegandhi, Amar; Brock, John C.; Sallenger, A.H.; Bonisteel, Jamie M.; Klipp, Emily S.; Wright, C. Wayne

2009-01-01

374

ATM Coastal Topography-Florida 2001: Eastern Panhandle  

USGS Publications Warehouse

These remotely sensed, geographically referenced elevation measurements of Lidar-derived first surface (FS) topography were produced collaboratively by the U.S. Geological Survey (USGS), Florida Integrated Science Center (FISC), St. Petersburg, FL, and the National Aeronautics and Space Administration (NASA), Wallops Flight Facility, VA. This project provides highly detailed and accurate datasets of the eastern Florida panhandle coastline, acquired October 2, 2001. The datasets are made available for use as a management tool to research scientists and natural resource managers. An innovative scanning Lidar instrument originally developed by NASA, and known as the Airborne Topographic Mapper (ATM), was used during data acquisition. The ATM system is a scanning Lidar system that measures high-resolution topography of the land surface and incorporates a green-wavelength laser operating at pulse rates of 2 to 10 kilohertz. Measurements from the laser-ranging device are coupled with data acquired from inertial navigation system (INS) attitude sensors and differentially corrected global positioning system (GPS) receivers to measure topography of the surface at accuracies of +/-15 centimeters. The nominal ATM platform is a Twin Otter or P-3 Orion aircraft, but the instrument may be deployed on a range of light aircraft. Elevation measurements were collected over the survey area using the ATM system, and the resulting data were then processed using the Airborne Lidar Processing System (ALPS), a custom-built processing system developed in a NASA-USGS collaboration. ALPS supports the exploration and processing of Lidar data in an interactive or batch mode. Modules for presurvey flight line definition, flight path plotting, Lidar raster and waveform investigation, and digital camera image playback have been developed. Processing algorithms have been developed to extract the range to the first and last significant return within each waveform. ALPS is routinely used to create maps that represent submerged or first surface topography.

Yates, Xan; Nayegandhi, Amar; Brock, John C.; Sallenger, A.H.; Bonisteel, Jamie M.; Klipp, Emily S.; Wright, C. Wayne

2009-01-01

375

ATM Coastal Topography-Texas, 2001: UTM Zone 14  

USGS Publications Warehouse

These remotely sensed, geographically referenced elevation measurements of lidar-derived first-surface (FS) topography were produced collaboratively by the U.S. Geological Survey (USGS), Florida Integrated Science Center (FISC), St. Petersburg, FL, and the National Aeronautics and Space Administration (NASA), Wallops Flight Facility, VA. This project provides highly detailed and accurate datasets of a portion of the Texas coastline within UTM zone 14, acquired October 12-13, 2001. The datasets are made available for use as a management tool to research scientists and natural-resource managers. An innovative scanning lidar instrument originally developed by NASA, and known as the Airborne Topographic Mapper (ATM), was used during data acquisition. The ATM system is a scanning lidar system that measures high-resolution topography of the land surface and incorporates a green-wavelength laser operating at pulse rates of 2 to 10 kilohertz. Measurements from the laser-ranging device are coupled with data acquired from inertial navigation system (INS) attitude sensors and differentially corrected global positioning system (GPS) receivers to measure topography of the surface at accuracies of +/-15 centimeters. The nominal ATM platform is a Twin Otter or P-3 Orion aircraft, but the instrument may be deployed on a range of light aircraft. Elevation measurements were collected over the survey area using the ATM system, and the resulting data were then processed using the Airborne Lidar Processing System (ALPS), a custom-built processing system developed in a NASA-USGS collaboration. ALPS supports the exploration and processing of lidar data in an interactive or batch mode. Modules for presurvey flight-line definition, flight-path plotting, lidar raster and waveform investigation, and digital camera image playback have been developed. Processing algorithms have been developed to extract the range to the first and last significant return within each waveform. ALPS is used routinely to create maps that represent submerged or first-surface topography.

Klipp, Emily S.; Nayegandhi, Amar; Brock, John C.; Sallenger, A.H.; Bonisteel, Jamie M.; Yates, Xan; Wright, C. Wayne

2009-01-01

376

Ultrawideband radar clutter measurements of forested terrain, 1991--1992  

SciTech Connect

The ultrawideband (UWB) radar clutter measurements project was conducted to provide radar clutter data for new ultrawideband radar systems which are currently under development. A particular goal of this project is to determine if conventional narrow band clutter data may be extrapolated to the UWB case. This report documents measurements conducted in 1991 and additional measurements conducted in 1992. The original project consisted of clutter measurements of forested terrain in the Olympic National Forest near Sequim, WA. The impulse radar system used a 30 kW peak impulse source with a 2 Gigasample/second digitizer to form a UHF (300--1000 MHz) ultrawideband impulse radar system. Additional measurements were conducted in parallel using a Systems Planning Corporation (SPC) step-chirp radar system. This system utilized pulse widths of 1330 nanoseconds over a bandwidth of 300--1000 MHz to obtain similar resolution to the impulse system. Due to the slow digitizer data throughput in the impulse radar system, data collection rates were significantly higher using the step-chirp system. Additional forest clutter measurements were undertaken in 1992 to increase the amount of data available, and especially to increase the amount of data from the impulse radar system.

Sheen, D.M.; Severtsen, R.H.; Prince, J.M.; Davis, K.C.; Collins, H.D.

1993-06-01

377

Imaging Radar Applications in the Death Valley Region  

NASA Technical Reports Server (NTRS)

Death Valley has had a long history as a testbed for remote sensing techniques (Gillespie, this conference). Along with visible-near infrared and thermal IR sensors, imaging radars have flown and orbited over the valley since the 1970's, yielding new insights into the geologic applications of that technology. More recently, radar interferometry has been used to derive digital topographic maps of the area, supplementing the USGS 7.5' digital quadrangles currently available for nearly the entire area. As for their shorter-wavelength brethren, imaging radars were tested early in their civilian history in Death Valley because it has a variety of surface types in a small area without the confounding effects of vegetation. In one of the classic references of these early radar studies, in a semi-quantitative way the response of an imaging radar to surface roughness near the radar wavelength, which typically ranges from about 1 cm to 1 m was explained. This laid the groundwork for applications of airborne and spaceborne radars to geologic problems in and regions. Radar's main advantages over other sensors stems from its active nature- supplying its own illumination makes it independent of solar illumination and it can also control the imaging geometry more accurately. Finally, its long wavelength allows it to peer through clouds, eliminating some of the problems of optical sensors, especially in perennially cloudy and polar areas.

Farr, Tom G.

1996-01-01

378

Radar images analysis for scattering surfaces characterization  

NASA Astrophysics Data System (ADS)

According to the different problems and techniques related to the detection and recognition of airplanes and vehicles moving on the Airport surface, the present work mainly deals with the processing of images gathered by a high-resolution radar sensor. The radar images used to test the investigated algorithms are relative to sequence of images obtained in some field experiments carried out by the Electronic Engineering Department of the University of Florence. The radar is the Ka band radar operating in the'Leonardo da Vinci' Airport in Fiumicino (Rome). The images obtained from the radar scan converter are digitized and putted in x, y, (pixel) co- ordinates. For a correct matching of the images, these are corrected in true geometrical co-ordinates (meters) on the basis of fixed points on an airport map. Correlating the airplane 2-D multipoint template with actual radar images, the value of the signal in the points involved in the template can be extracted. Results for a lot of observation show a typical response for the main section of the fuselage and the wings. For the fuselage, the back-scattered echo is low at the prow, became larger near the center on the aircraft and than it decrease again toward the tail. For the wings the signal is growing with a pretty regular slope from the fuselage to the tips, where the signal is the strongest.

Piazza, Enrico

1998-10-01

379

Venus - Global gravity and topography  

NASA Astrophysics Data System (ADS)

A new gravity field determination that has been produced combines both the Pioneer Venus Orbiter (PVO) and the Magellan Doppler radio data. Comparisons between this estimate, a spherical harmonic model of degree and order 21, and previous models show that significant improvements have been made. Results are displayed as gravity contours overlaying a topographic map. We also calculate a new spherical harmonic model of topography based on Magellan altimetry, with PVO altimetry included where gaps exist in the Magellan data. This model is also of degree and order 21, so in conjunction with the gravity model, Bouguer and isostatic anomaly maps can be produced. These results are very consistent with previous results, but reveal more spatial resolution in the higher latitudes.

McNamee, J. B.; Borderies, N. J.; Sjogren, W. L.

1993-05-01

380

Venus - Global gravity and topography  

NASA Technical Reports Server (NTRS)

A new gravity field determination that has been produced combines both the Pioneer Venus Orbiter (PVO) and the Magellan Doppler radio data. Comparisonsbetween this estimate, a spherical harmonic model of degree and order 21, and previous models show that significant improvements have been made. Results are displayed as gravity contours overlaying a topographic map. We also calculate a new spherical harmonic model of topography based on Magellan altimetry, with PVO altimetry included where gaps exist in the Magellan data. This model is also of degree and order 21, so in conjunction with the gravity model, Bouguer and isostatic anomaly maps can be produced. These results are very consistent with previous results, but reveal more spatial resolution in the higher latitudes.

Mcnamee, J. B.; Borderies, N. J.; Sjogren, W. L.

1993-01-01

381

Sentinel-3 Surface Topography Mission: Payload, Data Products and Cal/Val Preparation  

NASA Astrophysics Data System (ADS)

Sentinel-3 is an Earth observation satellite mission designed for GMES to ensure the long-term collection of high-quality measurements delivered in an operational manner to GMES ocean, land, atmospheric, emergency and security services. Primary sentinel-3 topography mission measurement requirements have been derived from GMES user needs as follows: • Sea surface topography (SSH), significant wave height (Hs) and surface wind speed derived over the global ocean to an equivalent accuracy and precision as that presently achieved by ENVISAT Radar Altimeter-2 (RA-2). • Enhanced surface topography measurements in the coastal zone, sea ice regions and over inland rivers, their tributaries and lakes. To address the above requirements, the Sentinel-3 Topography payload will carry a Synthetic Aperture Radar Altimeter (SRAL) instrument, a passive microwave radiometer (MWR) a GPS receiver and laser retro-reflector for precise orbit determination providing continuing the legacy of ENVISAT RA-2 and Cryosat. Three level of timeliness are defined within GMES for the S-3 Topography mission: • NRT products, delivered to the users in less than 3 hours after acquisition of data by the sensor, • Short time critical (STC) products, delivered to the users in less than 48 hours after the acquisition and, • Non-time critical (NTC) products delivered not later than 1 month after acquisition or from long-term archives. The Sentinel-3 topography data products will provide continuity of ENVISAT type measurement capability in Europe to determine sea, ice and land surface topography measurements with high accuracy, timely delivery and in a sustained operational manner for GMES users. The Sentinel-3 data will also provide fundamental inputs to a variety of value-adding downstream services for industry, government agencies, commercial users, service providers and appropriate regulatory authorities. The Calibration and Validation of the Sentinel-3 topography products will nominally rely on the cross-comparison with the ESA Envisat Altimetry mission and will be a significant challenge due to the stringent S-3 mission measurement requirements and their safeguarding all over the mission lifetime.

Féménias, P.; Rebhan, H.; Donlon, C.; Buongiorno, A.; Mavrocordatos, C.

2012-04-01

382

Digital Libraries  

NSDL National Science Digital Library

This projects introduces digital libraries, digital initiatives, search techniques, and the Instructional Architect Review Rubric. Digital Library Information : The Scope of the Digital Library D-Lib Journal article, 1998 2008 Joint Conference on Digital Libraries (JCDL) Annual meeting devoted to Digital Libraries Initiatives : Digital Libraries Initiative The Initiative's focus is to dramatically advance the means to collect, store, and organize information in digital forms, and make it available for searching, retrieval, and processing via communication networks -- all in ...

Heather

2008-09-29

383

Analysis of a digital chirp synthesizer  

SciTech Connect

Definite advantages are gained by using a chirp (linear-FM) waveform for radar pulse compression. Digital generation of this waveform provides programmability, predictability, and repeatability. Of the digital implementations considered, the digital chirp synthesizer is shown to have the most flexibility and is more readily miniaturized than the arbitrary waveform generator design. Elements and features of the digital chirp synthesizer are examined and design considerations are presented. A TTL breadboard circuit that was built demonstrates the soundness of the fundamental design of the digital chirp synthesizer concept. 10 refs., 18 figs., 10 tabs.

Allen, C.T.

1988-08-01

384

Radar, Target and Ranging.  

National Technical Information Service (NTIS)

This Test Operations Procedure (TOP) provides conventional test methods employing conventional test instrumentation for testing conventional radars. Single tests and subtests designed to test radar components, transmitters, receivers, antennas, etc., and ...

1984-01-01

385

Radar Absorbing Material Design.  

National Technical Information Service (NTIS)

Low observable platforms have extremely low radar cross section specifications that cannot be achieved by shaping alone. The application of radar absorbing material is necessary, in which case the appropriate constitutive parameters and thickness must be ...

C. K. Yuzcelik

2003-01-01

386

Enhanced characterization of niobium surface topography  

NASA Astrophysics Data System (ADS)

Surface topography characterization is a continuing issue for the superconducting radio frequency (SRF) particle accelerator community. Efforts are under way to both improve surface topography and its characterization and analysis using various techniques. In measurement of topography, power spectral density (PSD) is a promising method to quantify typical surface parameters and develop scale-specific interpretations. PSD can also be used to indicate how the process modifies topography at different scales. However, generating an accurate and meaningful topographic PSD of an SRF surface requires careful analysis and optimization. In this report, niobium surfaces with different process histories are sampled with atomic force microscopy and stylus profilometry and analyzed to trace topography evolution at different scales. An optimized PSD analysis protocol to serve SRF needs is presented.

Xu, Chen; Tian, Hui; Reece, Charles E.; Kelley, Michael J.

2011-12-01

387

Satellite radar interferometry - Two-dimensional phase unwrapping  

NASA Technical Reports Server (NTRS)

Interferometric synthetic aperture radar observations provide a means for obtaining high-resolution digital topographic maps from measurements of amplitude and phase of two complex radar images. The phase of the radar echoes may only be measured modulo 2 pi; however, the whole phase at each point in the image is needed to obtain elevations. An approach to 'unwrapping' the 2 pi ambiguities in the two-dimensional data set is presented. It is found that noise and geometrical radar layover corrupt measurements locally, and these local errors can propagate to form global phase errors that affect the entire image. It is shown that the local errors, or residues, can be readily identified and avoided in the global phase estimation. A rectified digital topographic map derived from the unwrapped phase values is presented.

Goldstein, Richard M.; Zebker, Howard A.; Werner, Charles L.

1988-01-01

388

Equatorial radar system  

Microsoft Academic Search

A large clear air radar with the sensitivity of an incoherent scatter radar for observing the whole equatorial atmosphere up to 1000 km altitude is now being designed in Japan. The radar will be built in Pontianak, West Kalimantan, Indonesia (0.03 deg N, 109.29 deg E). The system is a 47-MHz monostatic Doppler radar with an active phased array configuration

Shoichiro Fukao; Toshitaka Tsuda; Toru Sato; Susumu Kato

1990-01-01

389

Radar observations of asteroids  

NASA Technical Reports Server (NTRS)

The type of information that can be obtained from radar observations of asteroids includes sizes, shapes, spin vectors, and such surface characteristics as the decimeter-scale morphology, topographic relief, regolith porosity, and metal concentration. This paper describes the two radar facilities active in asteroid studies (the Arecibo Observatory in Puerto Rico and the Goldstone Radar in California) and techniques used in radar observations of asteroids. Results available for main-belt and near-earth asteroids are discussed.

Ostro, Steven J.

1989-01-01

390

Fifty years of radar  

Microsoft Academic Search

A development history of radar technology is presented, with attention to the driving of radar system design advances by the emergence of such weapon systems as long range aircraft and cruise missiles in World War II and the range of current applications for state-of-the-art radar techniques. The applications noted encompass over-the-horizon backscatter radars for aircraft detection at 500-1800 nmi ranges,

M. I. Skolnik

1985-01-01

391

Harmonic Radar Literature Harmonisk Radar - en Litteraturstudie.  

National Technical Information Service (NTIS)

A harmonic radar sends on a given frequency f sub o and receives on another frequency usually 3 f sub o. The overtone is generated on joints between the metal parts of the radar target. The generated high harmonic frequency is very weak, which is why this...

B. Jansson

1980-01-01

392

Harmonic radar literature  

Microsoft Academic Search

A harmonic radar sends on a given frequency f sub o and receives on another frequency usually 3 f sub o. The overtone is generated on joints between the metal parts of the radar target. The generated high harmonic frequency is very weak, which is why this radar has an extremely low range of detection. Natural objects in the target

B. Jansson

1980-01-01

393

Lunar radar backscatter studies  

NASA Technical Reports Server (NTRS)

The lunar surface material in the Plato area is characterized using Earth based visual, infrared, and radar signatures. Radar scattering in the lunar regolith with an existing optical scattering computer program is modeled. Mapping with 1 to 2 km resolution of the Moon using a 70 cm Arecibo radar is presented.

Thompson, T. W.

1979-01-01

394

Radar cross section measurements  

Microsoft Academic Search

The present status of radar cross section (RCS) measurements is addressed. The fundamental considerations and definitions associated with RCS measurements are reviewed, including radar waveform, polarization requirements, far-field requirements, and target dimensional scaling. Different types of measurement facilities are examined, including their range geometries, target support systems, calibration standards, and facility evaluation. Instrumentation radar requirements and designs are reviewed, and

Robert B. Dybdal

1987-01-01

395

Automatic Radar Waveform Recognition  

Microsoft Academic Search

In this paper, a system for automatically recognizing radar waveforms is introduced. This type of techniques are needed in various spectrum management, surveillance and cognitive radio or radar applications. The intercepted radar signal is classified to eight classes based on the pulse compression waveform: linear frequency modulation (LFM), discrete frequency codes (Costas codes), binary phase, and Frank, P1, P2, P3,

Jarmo Lundn; Visa Koivunen

2007-01-01

396

Controlling radar signature  

Microsoft Academic Search

Low observable technologies for military and tactical aircraft are reviewed including signature-reduction techniques and signal detection\\/jamming. Among the applications considered are low-signature sensors and the reduction of radar cross section in conjunction with radar-absorbing structures and materials. Technologies for reducing radar cross section are shown to present significant technological challenges, although they afford enhanced aircraft survivability.

Foulke

1992-01-01

397

Modern Radar Techniques for Geophysical Applications: Two Examples  

NASA Technical Reports Server (NTRS)

The last decade of the evolution of radar was heavily influenced by the rapid increase in the information processing capabilities. Advances in solid state radio HF devices, digital technology, computing architectures and software offered the designers to develop very efficient radars. In designing modern radars the emphasis goes towards the simplification of the system hardware, reduction of overall power, which is compensated by coding and real time signal processing techniques. Radars are commonly employed in geophysical radio soundings like probing the ionosphere; stratosphere-mesosphere measurement, weather forecast, GPR and radio-glaciology etc. In the laboratorio di Geofisica Ambientale of the Istituto Nazionale di Geofisica e Vulcanologia (INGV), Rome, Italy, we developed two pulse compression radars. The first is a HF radar called AIS-INGV; Advanced Ionospheric Sounder designed both for the purpose of research and for routine service of the HF radio wave propagation forecast. The second is a VHF radar called GLACIORADAR, which will be substituting the high power envelope radar used by the Italian Glaciological group. This will be employed in studying the sub glacial structures of Antarctica, giving information about layering, the bed rock and sub glacial lakes if present. These are low power radars, which heavily rely on advanced hardware and powerful real time signal processing. Additional information is included in the original extended abstract.

Arokiasamy, B. J.; Bianchi, C.; Sciacca, U.; Tutone, G.; Zirizzotti, A.; Zuccheretti, E.

2005-01-01

398

A transceiver module of the Mu radar  

NASA Technical Reports Server (NTRS)

The transceiver (TR) module of a middle and upper atmospheric radar is described. The TR module used in the radar is mainly composed of two units: a mixer (MIX unit) and a power amplifier (PA unit). The former generates the RF wave for transmission and converts the received echo to the IF signal. A 41.5-MHz local signal fed to mixers passes through a digitally controlled 8-bit phase shifter which can change its value up to 1,000 times in a second, so that the MU radar has the ability to steer its antenna direction quickly and flexibly. The MIX unit also contains a buffer amplifier and a gate for the transmitting signal and preamplifier for the received one whose noise figure is less than 5 dB. The PA unit amplifies the RF signal supplied from the MIX unit up to 63.7 dBm (2350 W), and feeds it to the crossed Yagi antenna.

Kato, S.; Ogawa, T.; Tsuda, T.; Sato, T.; Kimura, I.; Fukao, S.

1983-01-01

399

Radar image analysis utilizing junctive image metamorphosis  

NASA Astrophysics Data System (ADS)

A feasibility study was initiated to investigate the ability of algorithms developed for medical sonogram image analysis, to be trained for extraction of cartographic information from synthetic aperture radar imagery. BioComputer Research Inc. has applied proprietary `junctive image metamorphosis' algorithms to cancer cell recognition and identification in ultrasound prostate images. These algorithms have been shown to support automatic radar image feature detection and identification. Training set images were used to develop determinants for representative point, line and area features, which were used on test images to identify and localize the features of interest. The software is computationally conservative; operating on a PC platform in real time. The algorithms are robust; having applicability to be trained for feature recognition on any digital imagery, not just those formed from reflected energy, such as sonograms and radar images. Applications include land mass characterization, feature identification, target recognition, and change detection.

Krueger, Peter G.; Gouge, Sally B.; Gouge, Jim O.

1998-09-01

400

Delineate subsurface structures with ground penetrating radar  

SciTech Connect

High resolution ground penetrating radar (GPR) surveys were conducted at the Savannah River Site in South Carolina in late 1991 to demonstrate the radar techniques in imaging shallow utility and soil structures. Targets of interest at two selected sites, designated as H- and D-areas, were a buried backfilled trench, buried drums, geologic stratas, and water table. Multiple offset 2-D and single offset 3-D survey methods were used to acquire high resolution radar data. This digital data was processed using standard seismic processing software to enhance signal quality and improve resolution. Finally, using a graphics workstation, the 3D data was interpreted. In addition, a small 3D survey was acquired in The Woodlands, Texas, with very dense spatial sampling. This data set adequately demonstrated the potential of this technology in imaging subsurface features.

Wyatt, D.E. [Westinghouse Savannah River Co., Aiken, SC (United States); Hu, L.Z. [New Wave Technology, Houston, TX (United States); Ramaswamy, M. [Houston Advanced Research Center, Woodlands, TX (United States); Sexton, B.G. [Microseeps, Inc., Pittsburgh, PA (United States)

1992-10-01

401

Delineate subsurface structures with ground penetrating radar  

SciTech Connect

High resolution ground penetrating radar (GPR) surveys were conducted at the Savannah River Site in South Carolina in late 1991 to demonstrate the radar techniques in imaging shallow utility and soil structures. Targets of interest at two selected sites, designated as H- and D-areas, were a buried backfilled trench, buried drums, geologic stratas, and water table. Multiple offset 2-D and single offset 3-D survey methods were used to acquire high resolution radar data. This digital data was processed using standard seismic processing software to enhance signal quality and improve resolution. Finally, using a graphics workstation, the 3D data was interpreted. In addition, a small 3D survey was acquired in The Woodlands, Texas, with very dense spatial sampling. This data set adequately demonstrated the potential of this technology in imaging subsurface features.

Wyatt, D.E. (Westinghouse Savannah River Co., Aiken, SC (United States)); Hu, L.Z. (New Wave Technology, Houston, TX (United States)); Ramaswamy, M. (Houston Advanced Research Center, Woodlands, TX (United States)); Sexton, B.G. (Microseeps, Inc., Pittsburgh, PA (United States))

1992-01-01

402

Volume-imaging UHF radar measurement of atmospheric turbulence  

Microsoft Academic Search

The Turbulent Eddy Profiler (TEP) is a volume-imaging 915 MHz radar designed for atmospheric boundary layer turbulence studies. TEP is a pulsed, phased-array radar using digital beamforming techniques to provide four-dimensional images of refractive index fluctuations and wind vectors on grid scales comparable to those of large-eddy simulations. During October 1999, TEP was deployed during the Cooperative Atmospheric Surface Exchange

Jie Li; Francisco J. Lopez-Dekker; Turker Ince; S. J. Frasier

2000-01-01

403

Do you have a radar bill in your pocket?  

NSDL National Science Digital Library

This activity introduces students to radar bills (currency that has serial numbers that read the same forward and backward) and challenges them to estimate how frequently radar bills occur. The activity, part of the Figure This! collection of 80 math challenges emphasizing math in the real world, explains how symmetry and repeating patterns are important to mathematicians, scientists, and artists. The Hint tells students that our currency has eight-digit serial numbers, and the solution provides a table that shows the relationship between the number of digits in a serial number and the number of radar bills. Related questions ask students to solve similar problems with serial numbers that contain different numbers of digits. Answers to all questions and links to additional resources are provided. Copyright 2005 Eisenhower National Clearinghouse

National Council of Teachers of Mathematics (NCTM)

2002-01-01

404

Radar image preprocessing. [of SEASAT-A SAR data  

NASA Technical Reports Server (NTRS)

Standard image processing techniques are not applicable to radar images because of the coherent nature of the sensor. Therefore there is a need to develop preprocessing techniques for radar images which will then allow these standard methods to be applied. A random field model for radar image data is developed. This model describes the image data as the result of a multiplicative-convolved process. Standard techniques, those based on additive noise and homomorphic processing are not directly applicable to this class of sensor data. Therefore, a minimum mean square error (MMSE) filter was designed to treat this class of sensor data. The resulting filter was implemented in an adaptive format to account for changes in local statistics and edges. A radar image processing technique which provides the MMSE estimate inside homogeneous areas and tends to preserve edge structure was the result of this study. Digitally correlated Seasat-A synthetic aperture radar (SAR) imagery was used to test the technique.

Frost, V. S.; Stiles, J. A.; Holtzman, J. C.; Held, D. N.

1980-01-01

405

Enhancing the Arctic Mean Sea Surface and Mean Dynamic Topography with CryoSat-2 Data  

NASA Astrophysics Data System (ADS)

A reliable mean sea surface (MSS) is essential to derive a good mean dynamic topography (MDT) and for the estimation of short and long-term changes in the sea surface. The lack of satellite radar altimetry observations above 82 degrees latitude means that existing mean sea surface models have been unreliable in the Arctic Ocean. We here present the latest DTU mean sea surface and mean dynamic topography models that includes CryoSat-2 data to improve the reliability in the Arctic Ocean. In an attempt to extrapolate across the gap above 82 degrees latitude the previously models included ICESat data, gravimetrical geoids, ocean circulation models and various combinations hereof. Unfortunately cloud cover and the short periods of operation has a negative effect on the number of ICESat sea surface observations. DTU13MSS and DTU13MDT are the new generation of state of the art global high-resolution models that includes CryoSat-2 data to extend the satellite radar altimetry coverage up to 88 degrees latitude. Furthermore the SAR and SARin capability of CryoSat-2 dramatically increases the amount of useable sea surface returns in sea-ice covered areas compared to conventional radar altimeters like ENVISAT and ERS-1/2. With the inclusion of CryoSat-2 data the new mean sea surface is improved by more than 20 cm above 82 degrees latitude compared with the previous generation of mean sea surfaces.

Stenseng, Lars; Andersen, Ole B.; Knudsen, Per

2014-05-01

406

Radar Meteorology Tutorial  

NSDL National Science Digital Library

Brian McNoldy at Multi-community Environmental Storm Observatory (MESO) educates the public about the use of radar in meteorology in this pdf document. After reading about the history of radar, visitors can find out how radar can detect storms by transmitting a high-power beam of radiation. Students can learn how scatter, absorption, frequencies, scan angles, and moments impact the radar display. With the help of many example images, the author also discusses how to interpret the images collected. At the end of the online document, visitors can learn about the characteristics and capabilities of NEXRAD WSR-88D, the radar used throughout the United States.

Mcnoldy, Brian

2007-08-16

407

Maps of Mars Global Topography  

NASA Technical Reports Server (NTRS)

Maps of Mars' global topography. The projections are Mercator to 70o latitude and stereographic at the poles with the south pole at left and north pole at right. Note the elevation difference between the northern and southern hemispheres. The Tharsis volcano-tectonic province is centered near the equator in the longitude range 220o E to 300o E and contains the vast east-west trending Valles Marineris canyon system and several major volcanic shields including Olympus Mons (18o N, 225o E), Alba Patera (42o N, 252o E), Ascraeus Mons (12o N, 248o E), Pavonis Mons (0o, 247o E), and Arsia Mons (9o S, 239o E). Regions and structures discussed in the text include Solis Planum (25o S, 270o E), Lunae Planum (10o N, 290o E), and Claritas Fossae (30o S, 255o E). Major impact basins include Hellas (45o S, 70o E), Argyre (50o S, 320o E), Isidis (12o N, 88o E), and Utopia (45o N, 110o E). This analysis uses an areocentric coordinate convention with east longitude positive.

1999-01-01

408

A fully photonics-based coherent radar system.  

PubMed

The next generation of radar (radio detection and ranging) systems needs to be based on software-defined radio to adapt to variable environments, with higher carrier frequencies for smaller antennas and broadened bandwidth for increased resolution. Today's digital microwave components (synthesizers and analogue-to-digital converters) suffer from limited bandwidth with high noise at increasing frequencies, so that fully digital radar systems can work up to only a few gigahertz, and noisy analogue up- and downconversions are necessary for higher frequencies. In contrast, photonics provide high precision and ultrawide bandwidth, allowing both the flexible generation of extremely stable radio-frequency signals with arbitrary waveforms up to millimetre waves, and the detection of such signals and their precise direct digitization without downconversion. Until now, the photonics-based generation and detection of radio-frequency signals have been studied separately and have not been tested in a radar system. Here we present the development and the field trial results of a fully photonics-based coherent radar demonstrator carried out within the project PHODIR. The proposed architecture exploits a single pulsed laser for generating tunable radar signals and receiving their echoes, avoiding radio-frequency up- and downconversion and guaranteeing both the software-defined approach and high resolution. Its performance exceeds state-of-the-art electronics at carrier frequencies above two gigahertz, and the detection of non-cooperating aeroplanes confirms the effectiveness and expected precision of the system. PMID:24646997

Ghelfi, Paolo; Laghezza, Francesco; Scotti, Filippo; Serafino, Giovanni; Capria, Amerigo; Pinna, Sergio; Onori, Daniel; Porzi, Claudio; Scaffardi, Mirco; Malacarne, Antonio; Vercesi, Valeria; Lazzeri, Emma; Berizzi, Fabrizio; Bogoni, Antonella

2014-03-20

409

Radar image San Francisco Bay Area, California  

NASA Technical Reports Server (NTRS)

The San Francisco Bay Area in California and its surroundings are shown in this radar image from the Shuttle Radar Topography Mission (SRTM). On this image, smooth areas, such as the bay, lakes, roads and airport runways appear dark, while areas with buildings and trees appear bright. Downtown San Francisco is at the center and the city of Oakland is at the right across the San Francisco Bay. Some city areas, such as the South of Market district in San Francisco, appear bright due to the alignment of streets and buildings with respect to the incoming radar beam. Three of the bridges spanning the Bay are seen in this image. The Bay Bridge is in the center and extends from the city of San Francisco to Yerba Buena and Treasure Islands, and from there to Oakland. The Golden Gate Bridge is to the left and extends from San Francisco to Sausalito. The Richmond-San Rafael Bridge is in the upper right and extends from San Rafael to Richmond. Angel Island is the large island east of the Golden Gate Bridge, and lies north of the much smaller Alcatraz Island. The Alameda Naval Air Station is seen just below the Bay Bridge at the center of the image. Two major faults bounding the San Francisco-Oakland urban areas are visible on this image. The San Andreas fault, on the San Francisco peninsula, is seen on the left side of the image. The fault trace is the straight feature filled with linear reservoirs, which appear dark. The Hayward fault is the straight feature on the right side of the image between the urban areas and the hillier terrain to the east.

This radar image was acquired by just one of SRTM's two antennas and, consequently, does not show topographic data, but only the strength of the radar signal reflected from the ground. This signal, known as radar backscatter, provides insight into the nature of the surface, including its roughness, vegetation cover and urbanization. The overall faint striping pattern in the images is a data processing artifact due to the preliminary nature of this image product. These artifacts will be removed after further data processing.

This image was acquired by the Shuttle Radar Topography Mission (SRTM) aboard the Space Shuttle Endeavour, launched on February 11,2000. SRTM uses the same radar instrument that comprised the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR) that flew twice on the Space Shuttle Endeavour in 1994. The mission is designed to collect three-dimensional measurements of the Earth's surface. To collect the 3-D data, engineers added a 60-meter-long (200-foot) mast, installed additional C-band and X-band antennas, and improved tracking and navigation devices. The mission is a cooperative project between the National Aeronautics and Space Administration (NASA), the National Imagery and Mapping Agency (NIMA) of the U.S. Department of Defense (DoD), and the German and Italian Space agencies. It is managed by NASA's Jet Propulsion Laboratory, Pasadena, CA, for NASA's Earth Science Enterprise, Washington, DC.

Size: 38 km (24 miles) by 71 km (44 miles) Location: 37.7 deg. North lat., 122.2 deg. West lon. Orientation: North to the upper right Original Data Resolution: 30 meters (99 feet) Date Acquired: February 16, 2000

2000-01-01

410

Digital wires  

Microsoft Academic Search

We study hardware implementations of cellular automata as reliable, adjustable, and secure commication lines. We discuss energy efficient digital wires on a nano-scale, all-optical digital wires, and digital wires as power lines and present performance data of a prototype digital wire, a six cells wide and ten cells long Boolean network. We show that digital wires have the following advantages:

Alfred Hübler

2009-01-01

411

EAARL Coastal Topography - Northern Gulf of Mexico, 2007: First Surface  

USGS Publications Warehouse

These remotely sensed, geographically referenced elevation measurements of Lidar-derived first surface (FS) elevation data were produced as a collaborative effort between the U.S. Geological Survey (USGS), Florida Integrated Science Center (FISC), St. Petersburg, FL; the National Park Service (NPS), Gulf Coast Network, Lafayette, LA; and the National Aeronautics and Space Administration (NASA), Wallops Flight Facility, VA. The project provides highly detailed and accurate datasets of select barrier islands and peninsular regions of Louisiana, Mississippi, Alabama, and Florida, acquired June 27-30, 2007. The datasets are made available for use as a management tool to research scientists and natural resource managers. An innovative airborne Lidar instrument originally developed at the NASA Wallops Flight Facility, and known as the Experimental Advanced Airborne Research Lidar (EAARL), was used during data acquisition. The EAARL system is a raster-scanning, waveform-resolving, green-wavelength (532-nanometer) Lidar designed to map near-shore bathymetry, topography, and vegetation structure simultaneously. The EAARL sensor suite includes the raster-scanning, water-penetrating full-waveform adaptive Lidar, a down-looking red-green-blue (RGB) digital camera, a high-resolution multi-spectral color infrared (CIR) camera, two precision dual-frequency kinematic carrier-phase GPS receivers, and an integrated miniature digital inertial measurement unit which provide for submeter georeferencing of each laser sample. The nominal EAARL platform is a twin-engine Cessna 310 aircraft, but the instrument may be deployed on a range of light aircraft. A single pilot, a Lidar operator, and a data analyst constitute the crew for most survey operations. This sensor has the potential to make significant contributions in measuring sub-aerial and submarine coastal topography within cross-environmental surveys. Elevation measurements were collected over the survey area using the EAARL system, and the resulting data were then processed using the Airborne Lidar Processing System (ALPS), a custom-built processing system developed in a NASA-USGS collaboration. ALPS supports the exploration and processing of Lidar data in an interactive or batch mode. Modules for presurvey flight line definition, flight path plotting, Lidar raster and waveform investigation, and digital camera image playback have been developed. Processing algorithms have been developed to extract the range to the first and last significant return within each waveform. ALPS is used routinely to create maps that represent submerged or sub-aerial topography. Specialized filtering algorithms have been implemented to determine the 'bare earth' under vegetation from a point cloud of last return elevations.

Smith, Kathryn E. L.; Nayegandhi, Amar; Wright, C. Wayne; Bonisteel, Jamie M.; Brock, John C.

2009-01-01

412

EAARL coastal topography--Alligator Point, Louisiana, 2010  

USGS Publications Warehouse

This project provides highly detailed and accurate datasets of a portion of Alligator Point, Louisiana, acquired on March 5 and 6, 2010. The datasets are made available for use as a management tool to research scientists and natural-resource managers. An innovative airborne lidar instrument originally developed at the National Aeronautics and Space Administration (NASA) Wallops Flight Facility, and known as the Experimental Advanced Airborne Research Lidar (EAARL), was used during data acquisition. The EAARL system is a raster-scanning, waveform-resolving, green-wavelength (532-nanometer) lidar designed to map near-shore bathymetry, topography, and vegetation structure simultaneously. The EAARL sensor suite includes the raster-scanning, water-penetrating full-waveform adaptive lidar, a down-looking red-green-blue (RGB) digital camera, a high-resolution multispectral color-infrared (CIR) camera, two precision dual-frequency kinematic carrier-phase GPS receivers, and an integrated miniature digital inertial measurement unit, which provide for sub-meter georeferencing of each laser sample. The nominal EAARL platform is a twin-engine aircraft, but the instrument was deployed on a Pilatus PC-6. A single pilot, a lidar operator, and a data analyst constitute the crew for most survey operations. This sensor has the potential to make significant contributions in measuring sub-aerial and submarine coastal topography within cross-environmental surveys. Elevation measurements were collected over the survey area using the EAARL system, and the resulting data were then processed using the Airborne Lidar Processing System (ALPS), a custom-built processing system developed in a NASA-USGS collaboration. ALPS supports the exploration and processing of lidar data in an interactive or batch mode. Modules for presurvey flight-line definition, flight-path plotting, lidar raster and waveform investigation, and digital camera image playback have been developed. Processing algorithms have been developed to extract the range to the first and last significant return within each waveform. ALPS is used routinely to create maps that represent submerged or sub-aerial topography. Specialized filtering algorithms have been implemented to determine the "bare earth" under vegetation from a point cloud of last return elevations.

Nayegandhi, Amar; Bonisteel-Cormier, J. M.; Wright, C. W.; Brock, J. C.; Nagle, D. B.; Vivekanandan, Saisudha; Fredericks, Xan; Barras, J. A.

2012-01-01

413

Assessment of Digital Elevation Model (DEM) aggregation methods for hydrological modeling: Lake Chad basin, Africa  

NASA Astrophysics Data System (ADS)

Digital Elevation Models (DEMs) are used to compute the hydro-geomorphological variables required by distributed hydrological models. However, the resolution of the most precise DEMs is too fine to run these models over regional watersheds. DEMs therefore need to be aggregated to coarser resolutions, affecting both the representation of the land surface and the hydrological simulations. In the present paper, six algorithms (mean, median, mode, nearest neighbour, maximum and minimum) are used to aggregate the Shuttle Radar Topography Mission (SRTM) DEM from 3? (90 m) to 5' (10 km) in order to simulate the water balance of the Lake Chad basin (2.5 Mkm 2). Each of these methods is assessed with respect to selected hydro-geomorphological properties that influence Terrestrial Hydrology Model with Biogeochemistry (THMB) simulations, namely the drainage network, the Lake Chad bottom topography and the floodplain extent. The results show that mean and median methods produce a smoother representation of the topography. This smoothing involves the removing of the depressions governing the floodplain dynamics (floodplain area<5000 km 2) but it eliminates the spikes and wells responsible for deviations regarding the drainage network. By contrast, using other aggregation methods, a rougher relief representation enables the simulation of a higher floodplain area (>14,000 km 2 with the maximum or nearest neighbour) but results in anomalies concerning the drainage network. An aggregation procedure based on a variographic analysis of the SRTM data is therefore suggested. This consists of preliminary filtering of the 3? DEM in order to smooth spikes and wells, then resampling to 5' via the nearest neighbour method so as to preserve the representation of depressions. With the resulting DEM, the drainage network, the Lake Chad bathymetric curves and the simulated floodplain hydrology are consistent with the observations (3% underestimation for simulated evaporation volumes).

Le Coz, Mathieu; Delclaux, François; Genthon, Pierre; Favreau, Guillaume

2009-08-01

414

High Performance Waveform Generator Design for Full-Coherent Millimeter-Wave Radar  

Microsoft Academic Search

Millimeter-wave radar has attracted much attention as a replacement of some infrared or laser systems currently in use. In this paper, an approach of developing high performance waveform for full-coherent millimeter-wave radar is proposed. With good frequency configuration and optimal utilization of DDS (direct digital synthesizer), PLL (phase locked loop) and FPGA (field programming gate array), the developed radar waveform

Jingye Cait; Yishi Yang; Yuanwang Yang; Lianfu Liu; Xueyong Zhu

2007-01-01

415

Nearshore Processes, Currents and Directional Wave Spectra Monitoring Using Coherent and Non-coherent Imaging Radars  

Microsoft Academic Search

Two new radar systems have been developed for real-time measurement of near-shore processes, and results are presented for measurements of ocean wave spectra, near-shore sand bar structure, and ocean currents. The first is a non-coherent radar based on a modified version of the Sitex radar family, with a data acquisition system designed around an ISR digital receiver card. The card

D. Trizna; K. Hathaway

2007-01-01

416

Rendezvous radar for the orbital maneuvering vehicle  

NASA Technical Reports Server (NTRS)

This paper describes the development of the Rendezvous Radar Set (RRS) for the Orbital Maneuvering Vehicle (OMV) for the National Aeronautics and Space Administration (NASA). The RRS was to be used to locate, and then provide vectoring information to, target satellites (or Shuttle or Space Station) to aid the OMV in making a minimum-fuel-consumption approach and rendezvous. The RRS design is that of an X-Band, all solid-state, monopulse tracking, frequency hopping, pulse-Doppler radar system. The development of the radar was terminated when the OMV prime contract to TRW was terminated by NASA. At the time of the termination, the development was in the circuit design stage. The system design was virtually completed, the PDR had been held. The RRS design was based on Motorola's experiences, both in the design and production of radar systems for the US Army and in the design and production of hi-rel communications systems for NASA space programs. Experience in these fields was combined with the latest digital signal processor and micro-processor technology to design a light-weight, low-power, spaceborne radar. The antenna and antenna positioner (gimbals) technology developed for the RRS is now being used in the satellite-to-satellite communication link design for Motorola's Iridium telecommunications system.

Locke, John W.; Olds, Keith; Parks, Howard

1991-01-01

417

Spatial relationship of groundwater arsenic distribution with regional topography and water-table fluctuations in the shallow aquifers in Bangladesh  

NASA Astrophysics Data System (ADS)

The present study has examined the relationship of groundwater arsenic (As) levels in alluvial aquifers with topographic elevation, slope, and groundwater level on a large basinal-scale using high-resolution (90 m × 90 m) Shuttle Radar Topography Mission (SRTM) digital elevation model and water-table data in Bangladesh. Results show that high As (>50 ?g/l) tubewells are located in low-lying areas, where mean surface elevation is approximately 10 m. Similarly, high As concentrations are found within extremely low slopes (<0.7°) in the country. Groundwater elevation (weekly measured by Bangladesh Water Development Board) was mapped using water-table data from 950 shallow (depth <100 m) piezometers distributed over the entire country. The minimum, maximum and mean groundwater elevation maps for 2003 were generated using Universal Kriging interpolation method. High As tubewells are located mainly in the Ganges-Brahmaputra-Meghna delta, Sylhet Trough, and recent floodplains, where groundwater elevation in shallow aquifers is low with a mean value of 4.5 m above the Public Works Datum (PWD) level. Extremely low groundwater gradients (0.01-0.001 m/km) within the GBM delta complex hinder groundwater flow and cause slow flushing of aquifers. Low elevation and gentle slope favor accumulation of finer sediments, As-carrying iron-oxyhydroxide minerals, and abundant organic matter within floodplains and alluvial deposits. At low horizontal hydraulic gradients and under reducing conditions, As is released in groundwater by microbial activity, causing widespread contamination in the low-lying deltaic and floodplain areas, where As is being recycled with time due to complex biogeochemical processes.

Shamsudduha, M.; Marzen, L. J.; Uddin, A.; Lee, M.-K.; Saunders, J. A.

2009-06-01

418

Bed topography of Store Glacier, Greenland from high-resolution airborne gravity data  

NASA Astrophysics Data System (ADS)

Store Glacier is a major west Greenland outlet tidewater glacier draining an area of 30,000 square km into Uummannaq Fjord, flowing at a speed of 4.8 km per year at the terminus. The bed topography of the glacier is poorly known and the fjord bathymetry has only been partially surveyed for the first time in 2012. In this study, we present a new approach on the modeling of glacier thickness and sea floor bathymetry based on high resolution gravity constrained with other observations. In August 2012, we acquired a 250m spacing grid of free-air gravity data at a speed of 50 knots with accuracy at sub-milligal level. We constrain the 3D inversion of these gravity data with ship-borne bathymetry near the glacier front and radar-derived ice thickness on grounded ice to derive a seamless map of bed topography of grounded ice and sea floor. Comparison of the new topography with prior maps reveals vast differences. Prior bathymetry (IBCAO3) has an ice front grounded at sea level whereas observations show a depth of 550m. On grounded ice, the data reveal the subglacial topography at an unprecedented level of spatial details. We discuss the impact of the results on the modeling of the glacier flow and the understanding of its interaction with ocean thermal forcing and surface mass balance.

An, L.; Rignot, E. J.

2013-12-01

419

Ocean Surface Topography from Space: Educational Resources (title provided or enhanced by cataloger)  

NSDL National Science Digital Library

This portal provides access to a variety of educational resources from the National Aeronautics and Space Administration's (NASA) ocean surface topography program based on the missions of the TOPEX/Poseidon and Jason satellites. Materials include a kids' section with games, puzzles, and facts; educational entertainment; online resources for educators; information about useful books; and links to lesson plans and classroom activities. There is also a section on radar altimetry and its use in studying ocean topography, and a set of links to interactive exhibits demonstrating TOPEX/Poseidon technology. The class activities section includes hands-on demonstrations, skits, and an activity in which older students make models of the sea surface to match TOPEX/Poseidon satellite images of sea-surface height. There is also information on obtaining posters, brochures, CDs and slides, and a collection of links to additional resources and to frequently-asked-questions.