GRASS is an Open Source Geographic Information System that supports 2D and 3D raster (grid) and vector (point/line/polygon) data processing, analysis, and modeling capabilities. Grass supports dozens of raster and vector data formats for import and export, and may also connect to external geodatabases. GRASS includes both a Graphical User Interface (GUI) and a command line mode for interaction with the system. The command line capabilities of GRASS are also accessible through a variety of scripting languages (e.g. Python and Shell scripting) for automating geo-processing for repeated analyses and automated visualization or data processing. GRASS also integrates with many other statistical analysis packages such as R and is well documented.
GRASS has become a high quality cutting edge GIS software package with an almost unparalleled depth of offering directly within the main software package. Its functionality has been influenced by its usage and evaluation in numerous scientific studies. However, users need to invest time to get to know the user interface. In other words, there is a fairly high learning curve depending on user’s IT and GIS skills. Some users only use GRASS GIS for specific tasks only, but for daily work they use QGIS and ArcGIS.
GRASS has been under development for more than 30 years and it will continue to be a general-purpose GIS with a continuously improved structure and strong support for local adaptation for specific needs, particularly with respect to environmental studies.
The GRASS GIS software suite used for geospatial data management and analysis, image processing, graphics and maps production, spatial modeling, and visualization. It can handle raster, topological vector, image processing, and graphic data. Users can interface with the software features through a Graphical User Interface (GUI) or by “plugging into” GRASS via other software such as QGIS, allowing GRASS to be user-friendly.
There are over 300 core GRASS modules included in the GRASS GIS distribution, and over 100 add-on modules created by users and developers. The GRASS Add-ons page contains a growing list of links to GRASS GIS extensions, which are currently not part of the standard distributions. This allows many new features/functions to be easily added to the application.
http://grass.osgeo.org/download/addons/
Geographic information science widely used academic and commercial settings around the world, as well as by many governmental agencies and environmental consulting companies.
QGIS is free and open source cross-platform geographic information system software. Any user with an internet connection can visit one of the download sites and retrieve a copy of the software. There is no cost to the users and the source code is available under the terms of the GNU General Public License (GPL). Visit the GRASS GIS download page http://grass.osgeo.org/download/ to find a legitimate download package for the operating system of your choice.