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• GIS Development -- THE reference source for the GIS development community.
• GIS.com -- "Your Internet guide to Geographic Information Systems"
• GIS Cafe
• OpenGIS.org -- Open GIS Consortium OGC.  An industry consortium to develop publicly available geoprocessing specifications. 
• GIS Internet Resources -- If you don't find what you're looking for at The Contractor's Outpost, you will find it at GIS Internet Resources
• Modeling and Simulation  -- Modeling and simulation resources covering all areas including terrain modeling and visualization.
• Digital Data Sources -- A collection of on-line repositories of digital mapping, terrain and imagery data.
• Dod/MIL References -- Standards and field manuals related to Terrain Analysis and cartographic products.
• GeoVRML Org -- Working ground developing tools and standard practice for representing geographic data (e.g. maps and 3D models) on the web using VRML.
• SEDRIS -- Synthetic Environment Data Representation and Interchange Specification organization.
• SRM -- Spatial Reference Model
• SDTS -- Spatial Data Transfer Standard at the USGS.

• NGA -- United States Nation Geospatial Intelligence Agency, formerly known as NIMA, United States National Imagery and Mapping Agency
• Richmond Map Facility -- At the Defense Supply Center, Richmond, Va.  A clearinghouse for NGA products.
• USGS -- United States Geological Survey
• USGS Publications -- The publications section of the USGS.
• Navigator of the Navy -- Navy's focal point for the development of technical standards for navigation plans, data standards, training, and navigation system certification.
• NGS -- U.S. National Geodetic Survey
• NAVSTAR -- GPS Joint Program Office