A dual mode nonlinear interpolative compressor is described which compresses synthetic aperture radar images. The compression algorithm takes advantage of (1) the strong contrast between the target and the background, (2) the small percentage of target area compared with the total SAR image. The algorithm operates in two modes, i.e., an exact data transmission mode and an interpolative mode. The image is first segmented into small sub-blocks. The compressor then selects one of two modes according to the pixel values inside the block. If any pixel inside the block is above a predetermined threshold all pixels in this block are transmitted. On the other hand, if all pixels inside the block are below the threshold only one pixel is transmitted. At the receiver a two dimensional interpolation is then conducted to estimate the entire pixels in the block. Under the stationary assumption of the background information a second order statistic of the SAR image is used to derive the interpolative scheme. The compressor not only offers a high degree of exact target recovery but also offers a good recovery of the background information. Computer simulation results indicate that a good quality reconstruction can be accomplished with 1.5 bits per pixel.
"A Dual Mode Nonlinear Interpolative Compressor For SAR Images", Proc. SPIE 0066, Efficient Transmission of Pictorial Information, (30 October 1975); doi: 10.1117/12.965356; https://doi.org/10.1117/12.965356