Evaluating VHF-band SAR autofocus algorithms using a forest backscatter model

The objective of this paper is to assess the accuracy of an autofocus method developed for the Fast Factorized Back-Projection (FFBP) algorithm in simulated scenarios. We specifically address the question whether correlation measurements between subimages will suffice in the focusing process in one arbitrary merging step. A forest clutter model is used together with a model of the impulse responses to simulate two SAR sub-images of a forest. Correlation is used for sub-image matching and residual displacement errors are compiled using simulation. We conclude that the matching error increases with increased number of trees per resolution cell but can be restored with a larger image size in the correlation measurements. We also conclude that the autofocus method will be successful.