[mapguide-users] Incorrect NAD27 to NAD83 coordinate conversions

[Kayne M. Morvant]

Bruce,

You are right; the datum shift grid files do not get copied to the "nad" 
folder.  I did as you suggested and stopped the server, copied the grid 
files to the "nad" folder and restarted the server, but the coordinates are 
still incorrect.

Please let me know if you can confirm a defect or if there is anything else 
that I can try.

thanks,
Kayne

At 01:06 PM 2/13/2007 -0800, you wrote:
>Kayne,
>
>You don't have to rebuild the server to use the grid files. You will
>need to stop the server and add the grid files then restart the server.
>
>I don't think the datum shift grid files get copied to the "make
>install" location. Can you check this? You might have to manually just
>install the grid files to the install "nad" folder.
>
>MapGuide will do a datum shift automatically if it can, ie the grid
>files exist.
>
>I had a look at the source code and there might be a defect. I'll have
>to test it to verify. Please try the above and if it still fails then it
>is a defect.
>
>Thanks,
>Bruce
>
>
>-----Original Message-----
>From: mapguide-users-bounces at lists.osgeo.org
>[mailto:mapguide-users-bounces at lists.osgeo.org] On Behalf Of Kayne M.
>Morvant
>Sent: February 13, 2007 12:18 PM
>To: mapguide-users at lists.osgeo.org
>Subject: [mapguide-users] Incorrect NAD27 to NAD83 coordinate
>conversions
>
>Hi,
>
>I have a sdf data source with a coordinate system of Lat/Long NAD27.  I
>also have a map created in Mapguide Studio and the coordinate system is
>set
>to "UTM83-15 (UTM83-15)".  When I view the map, the coordinates are off
>by
>about 13 meters on the x coord. and 225 meters on the y coord.
>
>It appeared to me that the appropriate datum shifts were not being
>applied
>(and were not actually part of the default installation), so I did the
>following:
>- I stopped the Mapguide server.
>- I downloaded the datum shift grids (proj-datumgrid-1.3.zip from
>remotesensing.org/proj) and unzipped into the nad directory.
>- I executed a 'make clean', 'make', and 'make install' from the proj
>root
>directory.
>- I re-started the Mapguide server.
>
>When I completed the steps above, I viewed my map again but the
>coordinates
>were still incorrect.
>
>I have two questions:
>1) Did I follow the correct steps to add NAD27/NAD83 datum shifting
>support
>for proj4?
>2) How does Mapguide know whether or not to apply the datum shifts?
>
>Note: I am running MGOS 1.1 on Linux.
>
>-Kayne
>
>
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-----------------------------------------
Kayne Morvant
C & C Technologies, Inc.
730 E. Kaliste Saloom Rd.
Lafayette, LA 70508
Phone: 337-261-0660 ext. 3431
Direct Line: 337-735-3667
Fax: 337-261-0192
Email: kmm at cctechnol.com
-----------------------------------------