The Sites

There are various sites that are dedicated to free GIS software, providing foundations, forums, repositories, jumpstations, and
open access journals.

Open Source Geospatial Foundation
Created to support and build the highest-quality open source geospatial software. Our goal is to encourage the use and collaborative development of community-led projects. Join us by signing up to our mailing lists or check out the Getting Started page to become more involved.
OS Geo Journal
The OSGeo Journal is a digital publication containing case studies, news, tutorials, project updates and more. With a general aim at promoting, highlighting and educating readers about open source geospatial applications in general, but also provides updates on OSGeo projects. The Journal is also available in French
Open Source GIS
This effort represents an attempt to build a complete index of Open Source / Free GIS related software projects. The effort has some way to go, especially for projects in languages other than English. The definition of GIS has been kept loose to encompass a broad range of projects which deal with spatial data.
Open Geospatial Consortium
The Open Geospatial Consortium, Inc.® (OGC) is a non-profit, international, voluntary consensus standards organization that is leading the development of standards for geospatial and location based services.

The Packages

We give an overview of the most important programs and packages that CES
uses, or intents to use, or at least intents to review.

GRASS
Commonly referred to as GRASS, this is a Geographic Information System (GIS) used for geospatial data management and analysis, image processing, graphics/maps production, spatial modeling, and visualization. GRASS is currently used in academic and commercial settings around the world, as well as by many governmental agencies and environmental consulting companies. GRASS is official project of the Open Source Geospatial Foundation.
Quantum GIS (QGIS)
Quantum GIS (QGIS) is a user friendly Open Source Geographic Information System (GIS) that runs on Linux, Unix, Mac OSX, and Windows. QGIS supports vector, raster, and database formats. QGIS is licensed under the GNU General Public License. QGIS lets you browse and create map data on your computer. It supports many common spatial data formats (e.g. ESRI ShapeFile, geotiff). QGIS supports plugins to do things like display tracks from your GPS. QGIS is Open Source software and its free of cost (download here). We welcome contributions from our user community in the form of code contributions, bug fixes, bug reports, contributed documentation, advocacy and supporting other users on our mailing lists and forums. Financial contributions are also welcome.
MapServer
MapServer is an Open Source development environment for building spatially-enabled internet applications. MapServer is not a full-featured GIS system, nor does it aspire to be. Instead, MapServer excels at rendering spatial data (maps, images, and vector data) for the web.
Generic Mapping Tools (GMT)
GMT is an open source collection of ~60 tools for manipulating geographic and Cartesian data sets (including filtering, trend fitting, gridding, projecting, etc.) and producing Encapsulated PostScript File (EPS) illustrations ranging from simple x-y plots via contour maps to artificially illuminated surfaces and 3-D perspective views. GMT supports ~30 map projections and transformations and comes with support data such as GSHHS coastlines, rivers, and political boundaries. GMT is developed and maintained by Paul Wessel and Walter H. F. Smith with help from a global set of volunteers, and is supported by the National Science Foundation. It is released under the GNU General Public License
PostGIS
PostGIS adds support for geographic objects to the PostgreSQL object-relational database. In effect, PostGIS “spatially enables” the PostgreSQL server, allowing it to be used as a backend spatial database for geographic information systems (GIS), much like ESRI’s SDE or Oracle’s Spatial extension. PostGIS follows the OpenGIS “Simple Features Specification for SQL” and has been certified as compliant with the “Types and Functions” profile.
uDig
The goal of uDig is to provide a complete Java solution for desktop GIS data access, editing, and viewing.
CrimeStat
CrimeStat is a spatial statistics program for the analysis of crime incident locations, developed by Ned Levine & Associates under the direction of Ned Levine, PhD, that was funded by grants from the National Institute of Justice (grants 1997-IJ-CX-0040, 1999-IJ-CX-0044, 2002-IJ-CX-0007, and 2005-IJ-CX-K037). The program is Windows-based and interfaces with most desktop GIS programs. The purpose is to provide supplemental statistical tools to aid law enforcement agencies and criminal justice researchers in their crime mapping efforts. CrimeStat is being used by many police departments around the country as well as by criminal justice and other researchers. The new version is 3.0 (CrimeStat III).
OSSIM
OSSIM provides advanced geo-spatial image processing for remote sensing, photogrammetry, and Geographic Information Systems. Backed by an active open source software development community, OSSIM solutions have been deployed on a number of critical commercial and government systems.