Grass

Geographic Resources Analysis Support System (GRASS) is a general-purpose geographic information system (GIS) used for management, processing, analysis, modeling, and visualization of georeferenced data. Originally developed by the U.S. Army Corps of Engineers Construction Engineering Research Laboratories (1984–1993) as a tool for land management at military installations, its capabilities have been expanded to support geospatial analysis in the fields of hydrology, geography, ecology, business, and many others. GRASS is an open source/free software, released under the GNU General Public License (GPL) in 1999, and it is one of the founding projects [Page 218]of the Open Source Geospatial Foundation (OSGEO). It provides complete access to its source code written in the C programming language. GRASS is available for all commonly used operating systems, such as Linux, Mac OSX, and MS Windows.

GRASS is designed as an integrated set of over 300 modules that provide tools to process 2D raster and 3D voxel data, topological 2D/3D vector data, and imagery. Attributes are managed in a Structured Query Language-(SQL) based database management system, such as PostgreSQL/PostGIS. An extensive set of coordinate system transformations is supported through the PROJ library. The raster modules include map algebra, digital elevation modeling and watershed analysis, neighborhood operators, spatial statistics, line of sight, hydrologic modeling, solar irradiation, and many others. Vector data capabilities, such as digitizing, network analysis, and conversions between raster and vector data, are also provided. Image processing includes basic tools for image rectification and classification. Besides the standard 2D map display, an interactive visualization module allows users to view multiple surfaces and vector layers displayed in 3D space and create fly-through animations and dynamic surfaces. Volume visualization using isosurfaces and cross-sections is also available. Cartographic output is supported by a hardcopy postscript map output utility. The users can choose between a graphical user interface and a command line syntax especially useful for scripting. GRASS modules can also be accessed through popular external open source tools such as Quantum GIS.

The main components of the development and software maintenance are built on top of a highly automated Web-based infrastructure sponsored by the Center for Scientific and Technological Research (ITC-irst), in Trento, Italy, and Intevation GmbH, Germany, with numerous worldwide mirror sites. The software is developed by an international team of developers, collaborating over the Internet, who are also experienced GIS users. The Concurrent Versions System (CVS) provides network-transparent source control for groups of developers. The online bugtracking system, developers' and users' mailing lists, and wiki collaborative–environment–support software management and development.

To expand its capabilities, GRASS builds upon the efforts of many other open source/free GIS projects, such as the Geospatial Data Abstraction Library (GDAL), which is used for import and export of raster and vector data and seamless linking with other projects. A bridge to the R statistical language supports sophisticated geostatistical analysis. To support online mapping, GRASS can be directly linked to MapServer, which provides a powerful platform for dynamic Web mapping when extended with PostgreSQL and PostGIS. OSGEO foundation brings together a number of community-led geospatial software projects, including GRASS, and moves the collaboration between projects to a more formal level.

...