Lossless Compression of Classification Map Images

A classification map is an image that provides a low-level content description of a corresponding remote-sensing image. Each “pixel” in the map is the index of a class that represents some type of content, such as a type of vegetation or mineral, in the corresponding spatial location of the remote-sensing image. Classification maps generated onboard a spacecraft may be used as part of a region-of-interest image data compression scheme, and/or to provide low-data-volume summaries of the remote-sensing images. In either case, it is desirable to losslessly compress classification maps prior to transmission. In this article, we describe a technique for lossless compression of classification maps. Compression tests on sample classification maps indicate that our technique yields considerable improvement, e.g., a 15 to 40 percent bit-rate reduction, as compared to existing general-purpose lossless image compression methods.