Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. uDig is a GIS software program produced by a community led by Canadian-based consulting company Refractions Research. It is based on the Eclipse platform and features full layered Open Source GIS. It is written in Java and released under GNU Lesser General Public License. uDig has a walkthrough in Flash and also quick start directions for those who wish to complete a full version build to write plug-ins or contribute to the main build. Udig can use GRASS for complex vector operations and also embeds JGRASS and specialized hydrology tools from the Horton Machine. It supports shapefiles, PostGIS, WMS, and many other data sources natively.