Whitebox Geospatial Analysis Tools (GAT) is an open-source and cross-platform Geographic information system (GIS) and remote sensing software package that is distributed under the GNU General Public License. It has been developed by the members of the University of Guelph Centre for Hydrogeomatics and is intended for advanced geospatial analysis and data visualization in research and education settings. The package features a friendly graphical user interface (GUI) with help and documentation built into the dialog boxes for each of the more than 360 analysis tools. Users are also able to access extensive off-line and online help resources. The Whitebox GAT project started as a replacement for the Terrain Analysis System (TAS), a geospatial analysis software package written by John Lindsay. The current release support raster and vector (Shapefile) data structures.