Spatial data provided by the State of Michigan is distributed in a Michigan-specific projected coordinate system named Michigan GeoRef. The type of map projection is known as “Hotine Oblique Mercator”. This coordinate system uses NAD1983 as the datum, but the coordinates are unique to—and usable only in—Michigan. It is supported by ESRI software (ArcGIS) as well as DNRGarmin, which can use the ESRI projection information. The POSC code for NAD 1983 Michigan Georef (meters) is 102123.

In ArcGIS (Version 9.2, 9.3, and 10) the projection information (.prj) file can be found in Coordinate Systems : Projected Coordinate Systems : State Systems : NAD 1983 Michigan GeoRef (Meters).prj

In ArcGIS (Pre-version 9.2) the projection information (.prj) file can be found in Coordinate Systems : Projected Coordinate Systems : National Grids : NAD 1983 Michigan GeoRef (Meters).prj

More information on Michigan-specific coordinate systems is available from either Michigan State University or from the Michigan DNR