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  • 1
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    Radiometric correction of SAR images of varying terrain heights (1992)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: The advantages and disadvantages of three different approaches to solving the problem of the radiometric correction of synthetic aperture radar (SAR) images of varying terrain heights are presented. The first approach involves registration of a digital elevation model (DEM) of the terrain to the image, determination of the local elevation and incidence angles, and appropriate radiometric correction. The second approach uses a DEM generated from interferometric SAR data to derive the elevation and incidence angle maps. In the third approach, a monopulse technique is employed to determine the elevation angle only. The relative errors in radiometric correction between these approaches are assessed. Calibration errors are estimated using corner reflectors deployed within some of the scenes imaged by the Jet Propulsion Laboratory airborne SAR (JPL AIRSAR).
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: In: IGARSS '92; Proceedings of the 12th Annual International Geoscience and Remote Sensing Symposium, Houston, TX, May 26-29, 1992. Vol. 1 (A93-47551 20-43); p. 271-273.
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  • 2
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    Radar measurement of forested areas during OTTER (1992)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: To test a forest ecosystem model in the OTTER (Oregon ecosystem research) project, it is desirable to find forest canopy parameters via radar remote sensing measurements. Conventionally, forest biomass, along with quantities such as the leaf area index, drive the model. It is shown that the radar backscatter is not uniquely related to biomass. A sensitivity study is carried out using a forward scattering model to determine the variation of radar cross section as a function of several forest parameters. The results are used to find suitable quantities to recover via radar experiments. A parameter estimation scheme is developed to calculate some preliminary statistical properties of the forest.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: In: IGARSS '92; Proceedings of the 12th Annual International Geoscience and Remote Sensing Symposium, Houston, TX, May 26-29, 1992. Vol. 2 (A93-47551 20-43); p. 1135-1137.
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  • 3
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    Topographic mapping from interferometric synthetic aperture radar observations (1985)
    In:  CASI
    Details
    Publication Date: 2006-02-14
    Description: The production of high-resolution topographic maps derived from interferometric synthetic aperture radar observations of the Earth is reported. Topographic maps are typically determined from stereo-pair optical photographs. Vertical relief causes the same terrain to appear in a slightly different projection for differing look angles, and this shift in appearance is interpreted in terms of the height of the terrain. The radar interferometric approach is related to the stereo technique in that the terrain is viewed at two different angles; however, in this case, the angular separation of the antennas is extremely small, on the order of a milliradian or less, as compared to tens of degrees for the optical case. Thus, the geometrical distortion and subsequent rectification correction algorithms are much less severe in the reduction of interferometric data.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: NASA(JPL Aircraft SAR Workshop Proc.; p 41-44
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  • 4
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    Radio phase characteristics of terrain from multipolarized synthetic aperture radar data (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Recent advances in digital data acquisition and signal processing technology permit simultaneous measurement of the complex (amplitude and phase) radar backscatter from several polarization-diverse antennas. While absolute phase mesurements remain to be analyzed in detail. The differential phase of signals polarized parallel and perpendicular to the plane of incidence provide information on the scattering mechanisms that dominate the interaction of the radio waves with the terrain. Analysis of phase backscatter maps from a typical urban area yields a bimodal distribution with the two peaks separated by approximately 180 degrees, highly indicative of a dominant simple geometric one bounce-two bounce mechanism. Some maps of agricultural areas exhibit a similar distribution, however, other agricultural areas yield a distribution that, while still bimodal, consists of two peaks separated by about 110 deg. Still other agricultural areas exhibit a more complex distribution. All of the observed phase shifts appear to be independent of incidence angle from at least 20 deg to 55 deg, therefore the 110 degree shifts are inconsistent with both the geometric model used for the urban area and with common dielectric slab models.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
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  • 5
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    Modelling of backscatter from vegetation layers (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A simple way to build up a library of models which may be used to distinguish between the different types of vegetation and ground surfaces by means of their backscatter properties is presented. The curve of constant power received by the antenna (Gamma sphere) is calculated for the given Stokes Scattering Operator, and model parameters are adopted of the most similar library model Gamma sphere. Results calculated for a single scattering model resembling coniferous trees are compared with the Gamma spheres of a model resembling tropical region trees. The polarization which would minimize the effect of either the ground surface or the vegetation layer can be calculated and used to analyze the backscatter from the ground surface/vegetation layer combination, and enhance the power received from the desired part of the combination.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
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  • 6
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    Interferometric radar measurement of ocean surface currents (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A new method of measuring surface currents using an interferometric synthetic aperture radar is presented. An airborne implementation has been tested over San Francisco Bay near the time of maximum tidal flow, resulting in a map of the east-west component of the current. Only the line-of-sight component of velocity is measured by this technique. Where the SNR ratio was strongest, statistical fluctuations of less than 4 cm/s were observed for ocean patches of 60 x 60 m.
    Keywords: OCEANOGRAPHY
    Type: Nature (ISSN 0028-0836); 328; 707-709
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  • 7
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    Saturn's rings - Particle size distributions for thin layer model (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A model incorporating limited interaction between the incident energy and particles in the ring is considered which appears to be consistent with the multiple scattering process in Saturn's rings. The model allows for the small physical thickness of the rings and can be used to relate Voyager 1 observations of 3.6- and 13-cm wavelength microwave scatter from the rings to the ring particle size distribution function for particles with radii ranging from 0.001 to 20 m. This limited-scatter model yields solutions for particle size distribution functions for eight regions in the rings, which exhibit approximately inverse-cubic power-law behavior.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus (ISSN 0019-1035); 64; 531-548
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  • 8
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    Remote sensing of ocean currents (1989)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A method of remotely measuring near-surface ocean currents with a synthetic aperture radar (SAR) is described. The apparatus consists of a single SAR transmitter and two receiving antennas. The phase difference between SAR image scenes obtained from the antennas forms an interferogram that is directly proportional to the surface current. The first field test of this technique against conventional measurements gives estimates of mean currents accurate to order 20 percent, that is, root-mean-square errors of 5 to 10 centimeters per second in mean flows of 27 to 56 centimeters per second. If the full potential of the method could be realized with spacecraft, then it might be possible to routinely monitor the surface currents of the world's oceans.
    Keywords: OCEANOGRAPHY
    Type: Science (ISSN 0036-8075); 246; 1282-128
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  • 9
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    Topographic mapping from interferometric synthetic aperture radar observations (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Interferometric SAR observations are a basis for the generation of high resolution topographic maps of a region through the interpretation of interference fringes. The combination of height, along-track, and slant range measurements is sufficient for rectification of the radar imagery for cartographic applications, in addition to furnishing an accurate determination of the scene topography. Topographic maps have been derived on the basis of data recorded by both aircraft and Seasat-A satellite radars. A comparison of the maps obtained with U.S. Geological Survey Contour maps indicates a high degree of correlation between two sets of altitude data.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
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  • 10
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    Polarimetric radar measurements of a tropical rainforest (1991)
    In:  Other Sources
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    Publication Date: 2013-08-29
    Description: In Mar. 1990, the NASA/JPL DC-8 Airborne Synthetic Aperture Radar (AIRSAR) was flown over an area in northern Belize and the surrounding areas of Guatamala and Mexico. We have extracted the three-frequency polarimetric signatures of a variety of natural areas and have found that many appear to have a unique radar signature, if all polarizations and frequencies are examined.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Proceedings of the Third Airborne Synthetic Aperture Radar (AIRSAR) Workshop; p 223-229
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