Registration of synthetic aperture radar (SAR) images is a non-trivial task because of the significant speckle noise associated with them. We have performed the registration using 2-D cepstrum technique which has been verified to be more noise-tolerant and computationally more efficient than the conventional correlation methods. The cepstral peaks revealed liner translations between SAR image pairs, accurately. Further work is in progress to isolate the registration peaks from spurious peaks in a more reliable way than the present heuristic approach. Removal of speckle noise from the SAR images is also addressed. Spatial averaging is a standard technique used on SAR images to reduce speckle. However, this causes a loss of resolution. We have employed mathematical morphology techniques to remove more speckle than spatial averaging can, with little loss of resolution. Long, one-dimensional structuring elements in different orientations are used to filter speckle while maintaining the sharpness of region boundaries. Afterward, a small, two-dimensional structuring element is used to remove thin line elements. The targets appearing as small bright spots are separated from the original images by a thresholding operation and superimposed on the filtered images. The computational time required on a sequential machine is comparable to that for spatial averaging. In addition, like other morphological filters, this technique could be implemented on a real time parallel architecture. The improvement in resolution and noise reduction over the spatial averaging is demonstrated for images acquired at different wavelengths.

Date Published: 12 January 1993
PDF: 11 pages
Proc. SPIE 1771, Applications of Digital Image Processing XV, (12 January 1993); doi: 10.1117/12.139072

Published in SPIE Proceedings Vol. 1771:
Applications of Digital Image Processing XV
Andrew G. Tescher, Editor(s)