Comparison of the Compressed Aeronautical Chart and Compressed ARC DigitizedRaster Graphics Compression Techniques for ARC Digitized Raster Graphics Compression

摘要

This study compares two Defense Mapping Agency databases, the Navy StandardCompressed Aeronautical Chart (CAC) database and the Air Force Compressed Equal Arc-second Raster Chart Digitized Raster Graphics (CADRG) database, that are made up of compressed ARC digitized raster graphics data. There continues to be a large demand for raster map data in both the Department of Defense and commercial communities. Attention is focused on the various algorithms used to implement the compressions for each database. Both databases follow the same three basic steps, although the CADRG database employs some filtering techniques as well. Results show that the CADRG database, which achieves a 55:1 compression, outputs images that are slightly sharper, clearer, and of a higher resolution than the CAC images, due in large part to the additional filtering techniques. The CAC database, which achieves a 45:1 compression, was developed several years earlier than the CADRG database and was proven in combat situations during Operation Desert Storm. Both databases suffer loss of data during compression, and the actual differences between the images output by the databases are slight.