GRASS (Geographic Resources Analysis Support System) is a public domain raster based GIS, vector GIS, image processing system, and graphics production system. Created by the US Army Corps of Engineers, Constriction Engineering Research Laboratory (USA/CERL) and enhanced by many others, it is used extensively at government offices, universities and commercial organizations throughout the world. It is written mostly in C for various UNIX based machines. Linux is one of its more robust implementations.
GRASS contains over 40 programs to render images on monitor and paper; over 60 raster manipulation programs; over 30 vector manipulation programs; nearly 30 multi-spectral image processing manipulation programs; 16 data management programs; and 6 point file management programs.
GRASS’ strengths lie in several fields. The simple user interface makes it an ideal platform for those learning about GIS for the first time. Users wishing to write their own code can do so by examining existing source code, interfacing with the documented GIS libraries, and by using the GRASS Programmers’ Manual. This allows more sophisticated functionality to be fully integrated within GRASS.
Other strengths include GRASS’ pioneering of mixed resolutions in a data base, mixed geographic coverage areas in a data base, raster image compression techniques via run-length encoding and reclassification lookup tables, GRASS’ rescaling of display images on the fly to fill the display screen, plus its fundamental design criterion of powerful computer-assisted scientific analysis of environmental issues (as opposed to merely going for intricate cartographic output of relatively simple processes).
GRASS is usually supplied as free, non-copyright source code to be compiled on host machines. Some compiled binaries are also easily obtainable at no cost via the Internet. It runs on a variety of UNIX platforms.
By: David A. Hastings – The Geographic Information Systems: GRASS How To