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.
Micropolis is a city simulation game engine based on the original classic SimCity source code. Micropolis is based on the Tcl/Tk version of SimCity. It consists of the micropolis module, which is the engine recast as a C++ class; the cellengine module, which is a cellular automata machine engine; and the tileengine module, which is a Cairo based tile renderer. It is intended to be used with the OLPC's Sugar user interface environment, but layered so the core code is useful in other contexts.
GPSBabel converts waypoint data between about fifty file formats, including Magellan and Garmin serial, Garmin USB, Mapsource, Mapsend, Streets & Trips, Delorme, National Geographic, many PDA formats, and many others. It is endian and word-size safe, includes a GUI, and runs on a variety of operating systems. It also supports Groundspeak GPX extensions for geocaching.
Tkgeomap is a set of extensions to the Tcl/Tk scripting language for accessing, manipulating, and displaying geographic data. The extensions add commands that perform basic cartographic calculations, define and use projections, store data in lines and as named places, and display the data in canvas widgets.