MSc Dissertation: Amit Ashok


Adobe-PDF-downloadAshok, Amit. Implementation and Analysis of a Bayesian Approach to Topographic Reconstruction with Multiple Antenna Synthetic Aperture Radar Interferometry. MSc Dissertation. Department of Electrical Engineering, University of Cape Town, 2001.



Multiple antenna synthetic aperture radar SAR interferometry is a single pass interferometry technique for topographic mapping. A Bayesian model based approach to topographic reconstruction with multiple-antenna SAR interferometry, proposed by Dr A J Wilkinson, is implemented and analysed in this dissertation. The phase ambiguity reduction and data noise improvement achieved with multiple-antenna interferometry are explained from the basic principles of radar interferometry. The surface topography is modelled by a rectangular grid of discrete points on the ground, corresponding to the individual pixels in a SAR image. The position of each point is parameterised in terms of the angle of arrival of the received signal, represented by a pixel in the SAR image. Topographic reconstruction stated as an angle of arrival parameter estimation problem in a Bayesian inference framework.

To generate the necessary multiple-antenna data, an interferometric SAR simulator (based on a forward model for the SAR imaging process) is implemented. Two Bayesian estimation methods are implemented for estimating the angle of arrival parameter from the simulated multiple-antenna data. One estimation method uses a single pixel data vector to estimate the angle of arrival for a point in a image. The other estimation method employs a multiple pixel data vector with data from neighbouring pixels to estimate the angle of arrival for a point in the image. The likelihood and posterior distributions of angle of arrival obtained with the Bayesian estimation methods are analysed in detail for a three-antenna airborne SAR system. The ambiguities measured in the likelihood distribution of the angle of arrival obtained using the three antenna simulated dataset are verified from theoretical calculations. A measure of the accuracy of the angle of arrival estimate is formulated in terms of the standard deviation of posterior distribution obtained from the Bayesian analysis of the data. Finally, the Bayesian estimation methods are applied to a simulated three-antenna datset to demonstrate the topographic reconstruction process.



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