Digital image processing of orbital synthetic aperture radar

Abstract

Synthetic aperture radar (SAP) is gaining increasing importance in the field of remote sensing. The main feature of image data transmitted from orbital satellite synthetic aperture radar is all-weather performance, which explains its importance in
many applications. Unfortunately SAP image data is susceptible to "speckle noise", which means that considerable processing is required before full use can be made of the data. This thesis describes research performed into the
enhancement of linear features, corresponding to ships' wakes, in noisy SAP satellite images. A summary of noise reduction
techniques is described, and the suitability of each to the problem of enhancing linear features in SAR images is discussed. A survey of available hardware is also included, with an assessment of its suitability for the selected technique, namely the Radon transform.
A transputer network is described in detail, together with OCCAM software to perform the Radon transform within a few
seconds. The Radon transform, performed via the two-dimensional frequency domain, uses a technique based on the Fourier slice theorem, and in this thesis a previously reported ambiguity is confirmed and analysed.
The development of a new Radon transform is described, which enables transformation into Radon space (for contrast
enhancement), and back into image space, all via the frequency domain. This new transform was also implemented in OCCAM on the transputer network, and it is shown that the new transform has advantages over a previously reported line enhancement techniq'ie in that it eliminates the ambiguity found in the standard Radon transform, and reduces computation considerably when the inverse transform is also required.