COMPARISON OF IMPACT OF JPEG 2000 LOSSY COMPRESION WITH ECW LOSSY COMPRESSION TO DIGITAL ELEVATION MODEL

摘要

When dealing with a large set of geodata it is always necessary to use compression algorithms to lower their size. There are several algorithms that can be used for aerial (satellite) photos. The algorithms with a best compression ratio are nowadays based on a wavelet technique. Although digital elevation models (DEM) in a GRID form are a bit different to aerial (satellite) photos the wavelet algorithms can be used for a compression of DEM. The compression can be loss or loss less. The paper describes a comparison of two formats based on wavelet algorithm. The first one is well known as JPEG 2000 and the second one is well known as ECW (Enhanced Compression Wavelet). The goal of this research was to determine how the loss compression (high ratio) impacts quality of DEM. OpenJPEG library in GDAL was used to produce JPEG 2000 compressed file and ERDAS ECW SDK was used to produce ECW compressed file. GRASS GIS was used to compare compressed files and the impact of the compression.