The state of Michigan uses a customized version of the Clarke 1866 spheroid. The major and minor axes are multiplied by 1.0000382. The major axis is 6378206.4 and the minor axis is 6356583.8. This is true for both the current and old zones.
When writing Avenue code, use the
For more information, please refer to the ArcView Help topic 'recommended readings', especially the U.S. Geological Survey Professional Papers by John Snyder.