Thanks for all the suggestions – they have given me many possibilities to eliminate, but I still haven’t really got an answer to the original question.
Am I required to have proj.dll built with support for the datums/projections I want to use, or is it sufficient to set GDAL_DATA such that gcs.csv and pcs.csv are visible? I’m working in VB.NET, and I’m not confident I can rebuild PROJ with the required datums, so I wish to avoid if possible. I’d even be prepared to use SetGeogCS explicitly as I only use a few datums. If I use SetGeogCS, I can’t see what purpose proj.dll serves. I have set GDAL_DATA to the correct folder. I have checked that the datum numbers I use are in the gcs.csv file. From: [email protected] [mailto:[email protected]] On Behalf Of [email protected] Sent: Tuesday, October 18, 2011 4:12 AM To: [email protected] Subject: RE: [gdal-dev] Confused about datum transformations I’m not sure the code will help too much, but here are the relevant code fragments. I’m using a hand crafted VB.net wrapper which explains some of the syntax Private WGS84SRS As New OGRSpatialReference ' Coordinate system in WGS84 Private MapSRS As OGRSpatialReference ' Coordinate system of map Private ctWGS84toMap As OGRCoordinateTransformation ' Coordinate transform from WGS84 to map With WGS84SRS GDALError = .SetProjCS("WGS84 Datum") Debug.Assert(GDALError = OGRError.OGRERR_NONE, GetLastErrorMsg()) GDALError = .SetWellKnownGeogCS("WGS84") ' Define WGS84 coordinate system Debug.Assert(GDALError = OGRError.OGRERR_NONE, GetLastErrorMsg()) End With With MapSRS GDALError = .SetProjCS("Map coordinate system") Debug.Assert(GDALError = OGRError.OGRERR_NONE, GetLastErrorMsg()) GDALError = .ImportFromEPSG(3577) Debug.Assert(GDALError = OGRError.OGRERR_NONE, GetLastErrorMsg()) End With ctWGS84toMap = GDAL.CreateCoordinateTransformation(WGS84SRS, MapSRS) ' Create a coordinate transformation - WGS84 to map Debug.Assert(ctWGS84toMap IsNot Nothing, GetLastErrorMsg()) Marc, Can you provide the code leading to the error? On Tue, Oct 18, 2011 at 1:21 PM, Marc Hillman <[email protected]> wrote: I have a GIS database, and all data is stored in WGS84 datum. I have developed an application using GDAL, and I now need to translate my WGS84 coordinates to several different datums, depending what map is loaded. I seem to be going around in circles, and need a nudge in the right direction. I am defining an OGRSpatialReference for each datum (WGS84 and current map) and then attempting to create an OGRCoordinateTransformation for the transformation.. This last step fails with a PROJ.4 error (“No PROJ.4 translation for destination SRS, coordinate transformation initialization failed” My question is - Do I need PROJ.4 to do the translation? Can I not just use ImportFromWKT to define my OGRSpatialReference? If so, is there a nice canned list of all the WKT somewhere? I’m keen to avoid PROJ.4 if possible as I’m not sure I can build it. _______________________________________________ gdal-dev mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/gdal-dev -- Best regards, Chaitanya kumar CH. +91-9494447584 17.2416N 80.1426E No virus found in this message. Checked by AVG - www.avg.com Version: 2012.0.1831 / Virus Database: 2092/4558 - Release Date: 10/17/11 This email message is for the sole use of the intended recipient(s) and may contain confidential and privileged information. Any unauthorized review, use, disclosure or distribution is prohibited. If you are not the intended recipient, please contact the sender by reply email and delete the original message. No virus found in this message. Checked by AVG - www.avg.com Version: 2012.0.1831 / Virus Database: 2092/4558 - Release Date: 10/17/11
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