Journal of Digital Information Management Alexander Kolesnikov 7 2 2009 http://www.dirf.org/jdim/v7n2a4.asp A problem of progressive transmission of the large vector maps from spatial information systems to the clients over the Internet or by channels with narrow bandwidth is considered. First, a simplified version of the vector map is sent to a client. The client can manipulate with the data at the coarse resolution level and request finer version of the map or of a part of the map. The proposed algorithm includes optimal multiresolution polygonal approximation used jointly with multiresolution quantization and compression of the quantized data with arithmetic codes. The proposed approach demonstrates a high compression performance with optimal and heuristic algorithms for polygonal approximation.