GRASS (the Geographic Resources Analysis Support System) is a software raster- and vector-based GIS (Geographic Information System), image processing system, graphics production system, and spatial modeling system. It contains many modules for raster data manipulation, vector data manipulation, rendering images on the monitor or paper, multispectral image geocoding and processing, point data management and general data management. It also has tools for interfacing with digitizers, scanners, and the PostgreSQL, DBF, and ODBC connected databases. GRASS operates on all common operating systems.
SaVi is satellite visualization software that lets you create, run, examine, and modify satellite orbits in two and three dimensions. Simulations of Iridium, Globalstar, Galileo, GPS, and other satellite constellations are included. SaVi requires Tcl and Tk on a system with Unix libraries. SaVi works well with the 3D renderer Geomview. Geomview is optional, though recommended for its 3D rendering capabilities.
Engauge Digitizer is digitizing software that converts an image showing a graph or map into numbers. The image file can come from a scanner, digital camera, or screenshot. The numbers can be read on the screen, and written or copied to a spreadsheet. Highlights for beginners include an intuitive interface and extensive context-sensitive documentation. Highlights for experts include compensation for image distortion, cartesian and polar coordinates, linear and logarithmic coordinates, automatic scanning, graphical previews, and browser help.
Mapnik is a toolkit for developing GIS applications. At the core is a C++ shared library providing algorithms/patterns for spatial data access and visualization. Essentially a collection of geographic objects (map, layer, datasource, feature, and geometry), the library doesn't rely on "windowing systems" and can be deployed in any server environment. It is intended to play fair in a multi-threaded environment and is aimed primarily, but not exclusively, at Web-based development. High-level Python bindings (boost.python) facilitate rapid application development, targeting zope3, django, etc.
Earth3D visualizes the earth in realtime in a 3D view. One can rotate and zoom the view and fly around. Additional data layers can be added to the view, e.g. country flags and names. It uses data from NASA, USGS, the CIA, and the city of Osnabrück. The data is loaded on demand over the Internet.
geo-* is a set of tools for geocaching, including tools for accessing the www.geocaching.com, opencaching.com, opencaching.us, and navicache.com websites, tools for geocoding addresses and creating maps, and tools for manipulating Mapopolis place guide data. The focus of these tools is to provide a command line driven environment.
Roadnav is an in-car navigation system capable of running on a variety of operating systems, including Linux, Windows, and Mac OS X. It can obtain a car's present location from a GPS unit, plot street maps of the area, and provide verbal turn by turn directions to any location in the USA. It uses the free TIGER/Line files from the US Census Bureau to build the maps, along with the GNIS state and topical gazetteer data from the USGS to identify locations.