[Proj] does proj.4 work with Hotine Oblique Mercator?

OvV_HN ovv at hetnet.nl
Mon Jul 23 04:59:47 EST 2012

[Proj] does proj.4 work with Hotine Oblique Mercator?
Rick Graves gravesricharde at yahoo.com
Mon Jul 23 01:21:03 EST 2012


The Michigan Georef projection was discussed & verified on this list around 
the end of January 2007 and around the end of July 2006 (judging from dates 
of my notes).

With my code I get for:
lat = 42.25; lon = -83.75; // decimal coordinates
the Oblique Mercator Georef coordinates of:
x = 685493.0527; y = 191370.6792; // meters

This seems to be about right. It is within the bounding box and it is in the 
neighborhood of where Ann Arbor is, looking at the coordinates map on page 
16 of:

A primer on coordinate systems commonly used in Michigan
David P. Lusch
Department of geography, Remote sensing & GIS research and Outreach services 
Michigan State University
sept 2005

Michican Georef uses one ellipsoid: GRS80, not adjusted.
I guess you should supply to proj an alpha (azimuth at center of projection: 
337d15m20s), NO gamma (let the code calculate this (the answer should be 
equal to alpha), set no_off/no_uoff (to make it a Hotine-RSO), units are 

If you cannot reproduce my x,y coordinates, then there could be something 
wrong with proj's omerc in your version/implementation.

Oscar van Vlijmen

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