[Proj] Re: Michigan GeoRef

Melita Kennedy mkennedy2 at earthlink.net
Fri Jul 21 17:30:26 EDT 2006

Michigan GeoRef uses the same projection as State Plane Alaska zone 1. 
I don't know which projection this is in PROJ. We shouldn't need to implement 
another implementation of Hotine oblique Mercator to support Michigan GeoRef.

These are the official parameters from the Michigan DNR:

Projection: Oblique Mercator
Datum: NAD83
Ellipsoid: GRS80
Standard Units: Meters
Scale factor at projection's center: 0.9996
Longitude of projection's origin: 86° 00' 00" W
Latitude of projection's origin: 45° 18' 33" N
Azimuth at center of projection: 337.25556
False Easting: 2546731.496
False Northing: -4354009.816

Please note the azimuth value. The value in decimal degrees is not equal to the original
definition of 337d 15m 20s. Michigan GeoRef was originally defined to work with ArcInfo 
workstation which had a limitation in how many decimal places were allowed in the azimuth 
parameter. We've changed the ArcGIS version of the definition to match this--when we 
added the definition to the projection engine library, we used the DMS value--because 
Michigan clients were complaining that data wasn't lining up properly.


Melita Kennedy
ESRI Product Specialist
mkennedy at esri.com (but posting from mkennedy2 at earthlink.net)

-----Original Message-----
>Date: Thu, 20 Jul 2006 10:23:22 -0400
>From: "Clever, Max" <Maxc at spicergroup.com>
>Subject: [Proj] Michigan Georef projection support?
>To: <proj at lists.maptools.org>
>Hello Proj Developers,
>I've read a few posts and it looks like Gerald has already developed support for RSO's.  In the previous emails shown below, I have code written for Hotine Oblique Mercators that uses the Michigan Georef Parameters.  Hopefully the code you have written is more accurate.  I could not get the Northing accurate enough.  If you want the parameters for Michigan Georef they are available online if you google "Michigan Georef Projection".  This projection is very important for any Michigan Proj users since most freely available data is provided in Michigan Georef.  I think the last time I saw it in a proj format it was listed as a regular omerc which is not correct even though many sites describe it that way.  
>Anyhow, I was just wondering what the status was on the development of this projection
>-Max Clever

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