[mapguide-users] Incorrect NAD27 to NAD83 coordinate conversions

[Bruce Dechant]

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


_______________________________________________
mapguide-users mailing list
mapguide-users at lists.osgeo.org
http://lists.osgeo.org/mailman/listinfo/mapguide-users