Engineering topics

Domik, G.

Publications and source records attributed to Domik, G..

10 records

NASA NTRS1988

SIR-B stereo-radargrammetry of Australia

Results are reported from an ongoing program of radargrammetric experimentation with SIR-B data. Six stereo models of orbits over Australia were processed in an analytical stereo plotter. Height accuracies were up to + or - 25 m or 1.8 times the range resolution. This is better than in previous SIR-B stereo work, probably due to better image quality. Some inconsistencies were encountered between look angle geometries and height measurement accuracies. While general observations about earlier SIR-B stereo results were confirmed, inconsistencies with theoretical expectations could not be fully explained.

Leberl, F.↗

NASA NTRS1988

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

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.↗

NASA NTRS1987

Image based SAR product simulation for analysis

SAR product simulation serves to predict SAR image gray values for various flight paths. Input typically consists of a digital elevation model and backscatter curves. A new method is described of product simulation that employs also a real SAR input image for image simulation. This can be denoted as 'image-based simulation'. Different methods to perform this SAR prediction are presented and advantages and disadvantages discussed. Ascending and descending orbit images from NASA's SIR-B experiment were used for verification of the concept: input images from ascending orbits were converted into images from a descending orbit; the results are compared to the available real imagery to verify that the prediction technique produces meaningful image data.

Domik, G.↗

NASA NTRS1986

Radar stereomapping techniques and application to SIR-B images of Mt. Shasta

One of the goals of the SIR-B experiment was the definition of optimum radar incidence and intersection angles for radargrammetric stereoscopy by comparing the results from three separate data-reduction methods. To this end three overlapping images of the prime radargrammetric site (Mt. Shasta in northern California) were obtained, fewer than anticipated. This paper describes the mathematical basis for radar stereomapping, along with preliminary results from one of the methods (using a so-called 'analytical' stereoplotter) for the Mt. Shasta site. Height coordinate errors range from 60 to 170 m depending on the density (number per ground area) of ground control points used.

Leberl, F. W.↗

NASA NTRS1986

Multiple incidence angle SIR-B experiment over Argentina Stereo-radargrammetric analysis

Four overlapping Shuttle Imaging Radar-B (SIR-B) radar images were obtained across southern Argentina; these form a total of six stereo models with intersection angles ranging from 5 to 23 deg. This data set is uniquely suited for experimental evaluation of some basic assumptions on stereo-radargrammetry. Each stereo model was measured on a specially programmed photogrammetric analytical plotter; the resulting coordinates of ground points were compared with those from maps. It is concluded that accuracies are lower than expected at the larger stereo-intersection angles, amounting to about + or 60 m in each coordinate direction. This might be explained by limitations of the quality of stereofusion caused by look angle differences and specular point migration, backscatter differences due to different incidence angles, differences in azimuth directions, and image noise and speckle.

Leberl, F.↗

NASA NTRS1986

Multiple incidence angle SIR-B experiment over Argentina Generation of secondary image products

Original radar images may be geometrically and radio metrically distorted. This may be a particular problem when multiple angle imagery is analyzed and there is topographic relief in the area of interest. This paper describes a set of techniques designed to combine a multiple angle radar data set with a digital terrain elevation model, to generate a set of new images called secondary image products. These new images are geometrically rectified radar ortho-images radiometrically rectified images, and stereo ortho-images. These secondary images can then reliably be used for thematic interpretation.

Domik, G.↗

NASA NTRS1986

Space Shuttle radargrammetry results

Preliminary results on the radargrammetric processing of SIR-A and SIR-B data are presented. Radargrammetric processing was applied to images of the Trinity National Forest in Northern California, the islands of Cephalonia, Ithaka, and Sardegna, Mt. Shasta, and Cordon La Grasa, Argentina. The preliminary processing of the SIR-A and SIR-B data has produced digital elevation models, stereo models, and a contour map.

Leberl, F.↗

NASA NTRS1986

Developing tools for digital radar image data evaluation

The refinement of radar image analysis methods has led to a need for a systems approach to radar image processing software. Developments stimulated through satellite radar are combined with standard image processing techniques to create a user environment to manipulate and analyze airborne and satellite radar images. One aim is to create radar products for the user from the original data to enhance the ease of understanding the contents. The results are called secondary image products and derive from the original digital images. Another aim is to support interactive SAR image analysis. Software methods permit use of a digital height model to create ortho images, synthetic images, stereo-ortho images, radar maps or color combinations of different component products. Efforts are ongoing to integrate individual tools into a combined hardware/software environment for interactive radar image analysis.

Domik, G.↗

NASA NTRS1984

Analysis of radar images by means of digital terrain models

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.↗

NASA NTRS1984

SIR-B cartography and stereo topographic mapping

The SIR-B mapping experiment which will evaluate the utility of SAR images taken singularly, in pairs, and in combination with other data sets for cartographic, topographic, and thematic mapping, and determine the optimum configuration of a SAR system for future mapping mission is outlined. SIR-B is the first orbital imaging radar mission which will incorporate maintenance of geometric image fidelity along with careful calibration and documentation of internal timing and frequency parameters. This along and and the multiple incidence angle images of the same target which are necessary for stereoscopy and topographic mapping, make it the ideal opportunity for cartographic experimentation. It is emphasized that comprises a significant part of the overall experiment objectives.

Kobrick, M.↗