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Waite, W. P.

Publications and source records attributed to Waite, W. P..

35 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1981

Optimization of radar imaging system parameters for geological analysis

The use of radar image simulation to model terrain variation and determine optimum sensor parameters for geological analysis is described. Optimum incidence angle is determined by the simulation, which evaluates separately the discrimination of surface features possible due to terrain geometry and that due to terrain scattering. Depending on the relative relief, slope, and scattering cross section, optimum incidence angle may vary from 20 to 80 degrees. Large incident angle imagery (more than 60 deg) is best for the widest range of geological applications, but in many cases these large angles cannot be achieved by satellite systems. Low relief regions require low incidence angles (less than 30 deg), so a satellite system serving a broad range of applications should have at least two selectable angles of incidence.

Waite, W. P.↗
NASA NTRS1981

Using radar image simulation to assess relative geometric distortions inherent in radar imagery

A unique method for observing the relative contributions of backscatter and propagation effects is afforded by radar image simulation. Digital terrain data are used in modeling radar image formation. Backscatter and propagation effects are modeled separately. These are incorporated serially and the image expression of each is noted. Sequences of images are presented illustrating these effects over a range of slopes and angles of incidence. The conclusions reached are that at angles of incidence that are smaller than the average slope of the terrain in a region, propagation phenomena predominate. As the angle of incidence increases beyond this, the radar image portrays an increasingly faithful representation of the backscatter from the ground. It is also demonstrated that digital simulation affords an important tool for evaluating complex interactions between the ground and radar, for training users in radar image interpretation, and for selecting optimum sensor parameters for particular applications.

Kaupp, V. H.↗
NASA NTRS1981

Wetland mapping with imaging radar

An analysis of Seasat radar imagery is presented to identify the radar signature of vegetation-covered water surfaces. Imagery taken on Aug. 21, 1978 displayed anomalously high returns over swamp lands near Lafayette, LA. Landsat scans of the area two days later revealed uniform vegetation cover in the area, and ground examination found the area to be filled with cypress trees in swamps. Similar results were obtained during an overflight above a region of southeast Arkansas. Mechanisms producing the high degree of reflectance are explored, and the possibility that the strong return is due to an interaction of the vegetation cover and the specular water surface underneath is mentioned. Further studies to identify the exact mechanisms producing the anomalous returns are recommended, as well as optimization of the viewing angle for general classes of vegetation density.

Waite, W. P.↗
NASA NTRS1981

Geological terrain models

The initial phase of a program to determine the best interpretation strategy and sensor configuration for a radar remote sensing system for geologic applications is discussed. In this phase, terrain modeling and radar image simulation were used to perform parametric sensitivity studies. A relatively simple computer-generated terrain model is presented, and the data base, backscatter file, and transfer function for digital image simulation are described. Sets of images are presented that simulate the results obtained with an X-band radar from an altitude of 800 km and at three different terrain-illumination angles. The simulations include power maps, slant-range images, ground-range images, and ground-range images with statistical noise incorporated. It is concluded that digital image simulation and computer modeling provide cost-effective methods for evaluating terrain variations and sensor parameter changes, for predicting results, and for defining optimum sensor parameters.

Kaupp, V. H.↗
NASA NTRS1980

Data documentation for the bare soil experiment at the University of Arkansas

The reflectivities of several controlled moisture test plots were investigated. These test plots were of a similar soil texture which was clay loam and were prepared to give a desired initial soil moisture and density profile. Measurements were conducted on the plots as the soil water redistributed for both long term and diurnal cycles. These measurements included reflectivity, gravimetric and volumetric soil moisture, soil moisture potential, and soil temperature.

Waite, W. P.↗
NASA NTRS1978

Significance of dual polarized long wavelength radar for terrain analysis

Long wavelength systems with improved penetration capability have been considered to have the potential for minimizing the vegetation contribution and enhancing the surface return variations. L-band imagery of the Arkansas geologic test site provides confirmatory evidence of this effect. However, the increased wavelength increases the sensitivity to larger scale structure at relatively small incidence angles. The regularity of agricultural and urban scenes provides large components in the low frequency-large scale portion of the roughness spectrum that are highly sensitive to orientation. The addition of a cross polarized channel is shown to enable the interpreter to distinguish vegetation and orientational perturbations in the surface return.

Macdonald, H. C.↗
NASA NTRS1978

Long wavelength radar for geological analysis in vegetated terrain

In contrast to shorter wavelength radars, the range of returns from vegetated surfaces is appreciably less at L-band frequencies. However, the evaluation of differences in image quality due to changes in operational frequency is hindered by several system dissimilarities. In particular, a comparison of the Ka, X- and L-band radar imagery is difficult because of differences in 'effective' resolution. Though the physical resolution of these systems may be somewhat comparable, the inherent averaging of the real aperture systems (X-and Ka-) provides an apparent wider range of gray tones. This effect is related to the fact that at a scale where the resolution cell is discernable, the coherent scintillation of 'speckle' of the synthetic aperture L-band system masks tonal variations. This mismatch of effective resolution impedes detection of small changes in gray tone and makes subtle boundary changes less distinct.

Macdonald, H. C.↗
NASA NTRS1978

Dual polarized long wavelength radar for discrimination of agricultural land use

The scattered return of imaging radars is primarily sensitive to target structure or roughness and to composition of complex permittivity. The relative degree of penetration, or the depth of material to which the return is sensitive, also varies directly with the wavelength. Where vegetation can be eliminated as a factor, the surface return may be analyzed for variations in roughness or composition (primarily moisture content). L-band (25-cm) imagery has provided evidence that long-wavelength systems with improved penetration capability have the potential for minimizing the vegetation contribution and enhancing the surface return variations. However, the increased wavelength increases the sensitivity to large-scale structure. In the present paper, it is shown that addition of a cross polarized channel enables the interpreter to distinguish vegetation and orientation perturbations in the surface return.

Waite, W. P.↗
NASA NTRS1977

Preliminary geologic evaluation of L-band radar imagery: Arkansas test site

The relatively small angles of incidence (steep depression angles) of the L-band system provide minimal shadowing on terrain back-slopes and considerable foreshortening on terrain fore-slopes which sacrifice much of the topographic enhancement afforded by a more oblique angle of illumination. In addition, the dynamic range of the return from vegetated surfaces is substantially less for the L-band system, and many surface features defined primarily by subtle changes in vegetation are lost. In areas having terrain conditions similar to those of northern Arkansas, and where LANDSAT and shorter wavelength aircraft radar data are available, the value of the JPL L-band imagery as either a complimentary or supplementary geologic data source is not obvious.

Macdonald, H.↗
NASA NTRS1977

Landsat change detection can aid in water quality monitoring

Comparison between Landsat-1 and -2 imagery of Arkansas provided evidence of significant land use changes during the 1972-75 time period. Analysis of Arkansas historical water quality information has shown conclusively that whereas point source pollution generally can be detected by use of water quality data collected by state and federal agencies, sampling methodologies for nonpoint source contamination attributable to surface runoff are totally inadequate. The expensive undertaking of monitoring all nonpoint sources for numerous watersheds can be lessened by implementing Landsat change detection analyses.

Macdonald, H. C.↗
NASA NTRS1973

Imaging radars provide terrain texture and roughness parameters in semi-arid environments

Geoscience potentialities and limitations of available imaging radars are examined for alluvial valley-playa terrain environments. In such arid environments, a dual-sensor combination of an imaging radar with aerial photography is shown to provide a practical method for monitoring gross changes in surface textures of alluvial fans and playa surface conditions. It also appears feasible to infer surface materials and relative surface roughness with an improved degree of interpretive reliability.

Macdonald, H. C.↗
NASA NTRS1970

Snowfield mapping with K-band radar

Snow field mapping with K band radar imagery determining signal return difference with surrounding terrain, noting role of volume scattering and old snow structure

Macdonald, H. C.↗