[Proj] The Michigan Georef Projection Problem

[Clifford J Mugnier]

I stand corrected.  There is no "scaling" of the ellipsoid as is done in
Minnesota and Wisconsin.  However, the EPSG is not what I'd consider a
reliable source.  The Michigan DNR pdf file certainly is.

Sorry I can't help any further.

Cliff Mugnier
LSU
-----------------------------------------
Thanks for such a fast response,

Here is how it is described in my epsg file, which is correct according to
http://www.michigan.gov/documents/DNR_Map_Proj_and_MI_Georef_Info_20889_7.pdf

# NAD 1983 Michigan GeoRef Meters
<102123> +proj=omerc +lat_0=45.30916666666666 +lonc=-86
+alpha=337.255555555556 +k_0=0.9996 +x_0=2546731.496 +y_0=-4354009.816
+ellps=GRS80 +datum=NAD83 +units=m  no_defs <>


Michigan Georef is on the same datum and ellipsoid as the State Plane
projections so shouldn't an ellipsoid change be unnecessary?:

# NAD 1983 StatePlane Michigan South FIPS 2113 (US Feet)
<102690> +proj=lcc +lat_1=42.1 +lat_2=43.66666666666666 +lat_0=41.5
+lon_0=-84.36666666666666 +x_0=4000000 +y_0=0 +ellps=GRS80 +datum=NAD83
+to_meter=0.3048006096012192 no_defs <>

# NAD83 / Michigan South (International ft)
<2253> +proj=lcc +lat_1=43.66666666666666 +lat_2=42.1 +lat_0=41.5
+lon_0=-84.36666666666666 +x_0=3999999.999984 +y_0=0 +ellps=GRS80
+datum=NAD83 +to_meter=0.3048 +no_defs  no_defs <>




-----Original Message-----
From: Clifford J Mugnier [mailto:cjmce at lsu.edu]
Sent: Friday, December 17, 2004 4:10 PM
To: Clever, Max
Cc: proj at xserve.flids.com
Subject: Re: [Proj] The Michigan Georef Projection Problem






If memory serves me correctly, the Michigan Georef projection is just a
Hotine RSO with a differently-scaled ellipsoid to compensate for the
average elevation of the state.  To convert between that and standard State
Plane, you'd have to go through an ellipsoid change first.

Clifford J. Mugnier
Chief of Geodesy and
Associate Director,
CENTER FOR GEOINFORMATICS
Department of Civil Engineering
CEBA 3223A
LOUISIANA STATE UNIVERSITY
Baton Rouge, LA  70803
Voice and Facsimile:  (225) 578-8536 [Academic]
Voice and Facsimile:  (225) 578-4474 [Research]
======================================================
http://www.asprs.org/resources/GRIDS/
http://www.cee.lsu.edu/facultyStaff/mugnier/index.html
======================================================


Hello,

I have run into problems with the Michigan Georef projection and I think I
have read all the threads on it, which did not end up coming up with a
solution.  Have there been any fixes for this projection?  If not, then I
might need to work on Proj, which is a bit scary, but I still have the code
of a VB program I wrote that performs the transformation for michigan
georef to state plane and vice versa.  But, before I delve into Proj's
code, I just wanted to check on this listing if anybody has solved the
problem.

Until then, I will hope for the best.
Happy Holidays


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