From the PostGIS web site:

PostGIS adds support for geographic objects to the PostgreSQL object-relational database. In effect, PostGIS “spatially enables” the PostgreSQL server, allowing it to be used as a backend spatial database for geographic information systems (GIS), much like ESRI’s SDE or Oracle’s Spatial extension.

The data server can be downloaded from CodePlex. The data server is very easy to install. If you already have an existing PostGIS database, you only need to run the “Register.bat” batch script and the data server will be installed in GeoMedia. Like GeoMedia/Oracle, for read-only connections, you don’t even need to create a metadata schema! If you’d like to be able to PostGIS data, you’ll need to use the database utilities that come with the data server and setup the application metadata.

For those that are new to PostGIS, Intergraph provides a very nice PostGISGDOUserInfo.txt file that will guide you through the process of first installing PostGIS and then installing the data server. For those that would like to learn a lot more about PostGIS, there’s a recently released book named “PostGIS in Action“. Although I haven’t seen it myself, I’ve read many good things about it online.

One last note. If you’re a Windows Vista+ user, the data sever will NOT install unless you escalate a DOS window to “Administrator”. To do this, do the following:

1) In the start menu, type “CMD”

2) Right click on the result at the top and select “Run as administrator”

You’ll know that it worked as you’ll get back a “success” message box as opposed to a “error” message box.