The ExtentedCoordSyst.txt file is used with the [http://trac.osgeo.org/fdo/wiki/FdoSQLServerSpatialNotes, SQL Server Spatial provider] (for SQL Server 2008).

The ExtendedCoordSys.txt is composed of the following information (it can be copied and pasted into the file directly as // represent comments)

// [[BR]]
//The format for each line in this file is:[[BR]]
//[[BR]]
//     <SRID> <Coordinate System Name> <WKT>[[BR]]
//[[BR]]
// where:[[BR]]
//     SRID: is the SRID for each coordinate system. For all coordinate systems initially in the file, the SRID[[BR]]
//         is the coordinate system's EPSG number.[[BR]]
//[[BR]]
//     Coordinate System Name: the coordinate system name. [[BR]]
//[[BR]]
//     WKT: a string in Open Geospatial Well-Known Text format. [[BR]]
//[[BR]]
//         Only Geodetic or Projected coordinate systems can be listed so the WKT must start with either GEOGCS or [[BR]]
//         PROJCS. [[BR]]
//[[BR]]
// Each field must be separated by spaces (sorry, no tabs). [[BR]]
//[[BR]]
// Coordinate System Name can have embedded spaces (though this is probably unlikely). All words after the EPSG number,[[BR]]
// up to before the WKT, are treated as part of the Coordinate System name. [[BR]]
//[[BR]]
// The file must reside in the FDO com directory (A sub-directory named 'com' that is in the same directory as the [[BR]]
// SQLServerSpatial provider DLL). [[BR]]
//[[BR]]