[gdal-dev] Confused about datum transformations

[Chaitanya kumar CH]

Marc,

You don't need to rebuild proj.4; you are already using it. Since you were
able to use ogr2ogr to do the transformation, it works.

What you need to do is find out if the arguments you are passing to the
transformation builder are good. Especially 'MapSRS'. If it doesn't show any
problem, plug some debug messages in the OSR code in ogrct.cpp and rebuild
gdal.

On Wed, Oct 19, 2011 at 12:46 PM, <dev4cx4m9z at snkmail.com> wrote:

> 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:* gdal-dev-bounces at lists.osgeo.org [mailto:
> gdal-dev-bounces at lists.osgeo.org] *On Behalf Of *dev4cx4m9z at snkmail.com
> *Sent:* Tuesday, October 18, 2011 4:12 AM
> *To:* gdal-dev at lists.osgeo.org
> *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 <dev4cx4m9z at snkmail.com>
> 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
> gdal-dev at lists.osgeo.org
> 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*
> ***
>
> _______________________________________________
> gdal-dev mailing list
> gdal-dev at lists.osgeo.org
> http://lists.osgeo.org/mailman/listinfo/gdal-dev
>



-- 
Best regards,
Chaitanya kumar CH.

+91-9494447584
17.2416N 80.1426E
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.osgeo.org/pipermail/gdal-dev/attachments/20111019/18c9f30a/attachment.html