TerraGear is a collection of open-source tools and rendering libraries which can transform publically available GIS data in 3D representations (i.e. 3D models or 3D maps) of the earth for use in real time rendering projects. Terragear can import 3D data sets such as DEM terrain grids, 2D polygon data sets such as coastlines, city outlines, lake outlines, and 2D raster data sets such as the 1km NAOO land use/land cover data. It also has tools for generating realistic airports, runways, and lighting based on available FAA data.
TerraGear is the primary tool used to generate the world wide scenery for the FlightGear project.