[mapguide-users] Access DB and coord systems

[Dave Wilson]

I can't see anything obvious from the XML.
 
What UTM coordinate system are you using?
 
Does the LL83 data actaully map within the UTM coordinate system? I know
this is a dumb question, but it's possible to mistakenly try to display
Hawaii data from LL83/4 in a UTM for say Montana which will never work.
If the map was orginally created with the data in UTM it's extent was
set to that of the first layer imported. This may not be the full extent
of the UTM coordinate system. Are you sure that when you zoom out the
data isn't in the correct place within the UTM extent and it's just a
zoom issue?
 
Dave

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From: Gord McKenzie [mailto:gord.mckenzie at canam.com] 
Sent: Thursday, August 31, 2006 8:10 AM
To: users at mapguide.osgeo.org
Subject: RE: [mapguide-users] Access DB and coord systems



Here is the result of my getresourcedata query.  Does this help clarify
where the problem is occurring?

 

As this happens right in the Autodesk Studio tool, shipping version, I
wonder if anyone from Autodesk can tell me what they think might be
going on here.

 

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From: Traian Stanev [mailto:traian.stanev at autodesk.com] 
Sent: Wednesday, August 30, 2006 4:11 PM
To: users at mapguide.osgeo.org
Subject: RE: [mapguide-users] Access DB and coord systems

 

 

Reprojection is done on a stream of data that is independent of the
source -- SDF, SHP, Oracle, etc. all pass through the same code for
reprojection. That's why it has to be a problem with the way that code
gets the coordinate system from the FDO provider (or the provider giving
it the wrong coordinate system). 

 

It makes sense that the data still displays because one of the possible
fallbacks in that code is to default to identity transform. So your LL
data will (incorrectly in this case) display at UTM coordinates close to
the UTM origin (between 0 and 180 meters).

 

	-----Original Message----- 
	From: Gord McKenzie [mailto:gord.mckenzie at canam.com] 
	Sent: Wed 8/30/2006 5:33 PM 
	To: users at mapguide.osgeo.org 
	Cc: 
	Subject: RE: [mapguide-users] Access DB and coord systems

	Not sure if this means much but the data is actually drawn on
the map.  If I pan and zoom to the LL coordinates I find my data is
there.  So my source data is in LL and my map in UTM.  The weblayout
preview shows me that I am zoomed to the extents of my UTM window.
Never the less, the data from my access table is still drawn at it's LL
coordinates.  Going to try this with a SQL Server table and see if that
makes any difference.

	 

	I used the getresourcedata function to get an XML output of the
Access data source and it would seem to confirm that it knows about LL83
and only LL83.

	 

	Anyone actually successfully transforming LL cords from a DB to
something else and if so what database are you using?

	 

	Gord 

	 

	
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	From: Traian Stanev [mailto:traian.stanev at autodesk.com] 
	Sent: Wednesday, August 30, 2006 1:40 PM
	To: users at mapguide.osgeo.org
	Subject: RE: [mapguide-users] Access DB and coord systems

	 

	 

	One thing I can think of would be if your ODBC connection lists
more than one coordinate system when queried by the server and the
server then could end up using the wrong one for repro, which would
result in the behavior you describe. Another possibility is that it
didn't parse the WKT string correctly for the ODBC connection, although
that's unlikely, given that LL83 is a popular one.

	 

	Traian

	 

	
  _____  


	From: Gord McKenzie [mailto:gord.mckenzie at canam.com] 
	Sent: Wednesday, August 30, 2006 3:34 PM
	To: users at mapguide.osgeo.org
	Subject: [mapguide-users] Access DB and coord systems

	I have a table in access with lat and long.  I can create and
successfully Test Connection to the ODBC database which is identified as
LL83.  I can create a layer, a map and a web layout that will show this
data.  If I set my map coord system to UTM zone, the data is not
transformed.  I can add shape and sdf layers that are LL83 source and
reproject just fine.  Only DB data sources don't seem to want to
reproject.

	 

	Can anyone offer any reason or advice?

	 

	Thanks

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