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This thesis is concerned with the geocoding of Synthetic Aperture Radar (SAR) images and the use of stereo SAR images. The work was carried out as part of the preparation for the launch of the ERS-1 sateffite, due in July 1991, which will carry a SAR sensor. There are two basic approaches to geocoding: image-to-object and object-to-image. Both of these methods have been analysed and assessed on experimental data, namely SIR-B imagery of Mount Shasta. Each type of geocoding requires the solution of nonlinear equations. It has been shown that if the parameters which control the geocoding process are given to a good degree of accuracy, each method can give good results. The effect of inaccuracies in the estimation of these parameters has also been analysed. It was found that there was a predominantly linear response to parameter error in both types of geocoding. Experimental investigations into the effects of the resampling, inherent in operational geocoding, showed that the statistical properties of the resulting image may be severely corrupted with pixel values of less than zero being obtained. This discovery has subsequently been given theoretical support. Height can be determined from stereo pairs of images and digital elevation models can thus be produced, aiding both geocoding and topographic mapping. Existing approaches to SAR/SAR stereo all appear to be based on photograinmetric methods. An alternative, analytic approach, believed to be novel, is described and applied to the same Mount Shasta imagery. Using this method, with accurately-known controlling parameters, correspondence with ground data is excellent. However, an analysis of the sensitivity of the approach to inaccuracies in the controlling parameters shows that the method is extremely sensitive to error. The possibility of combining SAR and optical/infrared imagery for stereometric purposes is also discussed from a theoretical viewpoint.

The proposal is made that very small changes in gravitational field could be detected by monitoring a cell of heated fluid. Variations in gravity would be observed by their effect on the convection in the fluid cell. It is proposed that the convection patterns be observed by using an interferometer to image the temperature gradient in the fluid by utilising the effect of temperature variations on the refractive index of the fluid. It was proposed that this system may be able to detect changes in the Earth's gravitational field from orbit. The possibility of using the NASA GAS programme to perform a space flight test of this proposal was suggested. Activities in this programme were therefore surveyed and a proposal made. The primary experimental results were recorded in the form of convection images which were later processed on the ground to extract information. Research has been carried out in this area as investigation has shown that existing image processing techniques are not suitable to process the anticipated fringe images. Meanwhile design and development of a GAS experiment was performed. This was undertaken in liaison with NASA in order to achieve the required safety approvals for flight. Subsequently the flight experiment was performed aboard the Space Shuttle Endeavour during the STS-77 mission launched on the 19th May 1996. As a result of this project an image processing system for the analysis of interferogram images of convection has been developed and an experiment to image convection in microgravity, with a view to analysing its use for the detection of changes in gravity has been performed.

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