Three key areas of controversy in synthetic-aperture radar (SAR) imaging of ocean surface waves are considered: first, the nature of Bragg scattering; second, the role, magnitude, and calculation of the scene coherence time; and third, the relevant ocean wave velocities for coherent Doppler modulations.
This work begins with a re-derivation and extension of existing SAR imaging theory for point and diffuse targets. Generic, relatively simple, closed-form expressions for the impulse response, the resolution, and the image bandwidth summarize this unified treatment. Theoretical differences between the imagery of point and diffuse targets are pointed out. Based upon these fundamental differences, a statistical testing procedure is formulated to address the question of scene target density.
Background ocean surface wave theory is outlined in preparation for discussions of SAR ocean imaging. Of central importance is the role of the phase velocity, which is the speed of translation of the mean pattern of reflectivity, and the orbital motion, which leads to coherent (phase) modulation, and hence to velocity bunching, acceleration defocus, and target decorrelation.
Based upon this theoretical background, one- and two-dimensional simulation models
are developed. The one-dimensional simulation addresses the effects of various parameters
upon the mean image contrast in a velocity bunching model and guides the development of the two-dimensional simulation. The two-dimensional simulation is unique because each target which constitutes the scene is explicitly considered. This leads to a degree of control and flexibility which is not available from actual SAR imagery.
Qualitative and quantitative comparisons are drawn between the simulated and actual SAR imagery to address the key areas of controversy. The assertion that Bragg scattering is a coherent process is defended, despite inability to conclusively verify this using SEASAT data. Comparisons between simulation and C-SAR imagery of waves propagating into ice verify the roles of the scene coherence time and the wave phase velocity. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate
| Identifer | oai:union.ndltd.org:UBC/oai:circle.library.ubc.ca:2429/27556 |
| Date | January 1987 |
| Creators | Vachon, Paris W. |
| Publisher | University of British Columbia |
| Source Sets | University of British Columbia |
| Language | English |
| Detected Language | English |
| Type | Text, Thesis/Dissertation |
| Rights | For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use. |
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