This presentation will focus on the benefits Open Source Software can provide for the deployment of Internet-based Geographic Information Systems ( Apache GIS GIS software Homeland Defense Linux MapServer ) services. Open Source GIS software is in a position to play an important roll in breaking down barriers to the use of public spatial data, democratizing the use of GIS data in the US and around the world. In the US, Open Source GIS will be critical to the promotion of open spatial data standards as defined by the Open GIS Consortium, and to the development of a public infrastructure for spatial data. Some of the well-understood benefits of Open Source software, including security and robustness within networked environments, make Open Source GIS especially attractive in the context of . "Best of breed" web-based exists that can complete head on with proprietary software as and have done within their markets. There are many great Open Source GIS projects. A particular platform, , will be discussed in detail and demonstrated for this presentation. MapServer was originally developed by NASA and is now maintained by a worldwide group of developers.