[Proj] GDM2000 for Malaysia

[Frank Warmerdam]

Bjørn Krangnes wrote:
> I have now been looking at this again and my findings are that the program
> cs2cs is working correct while using gdal in a c# enviroment gives
> problems. Without the use3 of no_uoff and rot_conv both programs gives the
>  same result:
> ** cs2cs
> cs2cs +proj=longlat +ellps=GRS80 +no_defs +to +proj=omerc +
> lat_0=4 +lonc=102.25 +alpha=323.0257964666666 +k=0.99984 +x_0=804671
> +y_0=0 +ellps=GRS80 +units=m +no_defs
> 103.64025987222223 1.827764875
> 959373.97       -240050.80 0.000
> 
> **gdal
> inn = inpGDM2000.ImportFromProj4("+proj=longlat +ellps=GRS80 +no_defs  <>");
> out = outRSO.ImportFromProj4("+proj=omerc +lat_0=4 +lonc=102.25
> +alpha=323.0257964666666 +k=0.99984 +x_0=804671 +y_0=0 +ellps=GRS80
> +units=m +no_defs <>")
> 959373.969 -240050.800
> 
> with no_uoff and rot_conv option
> ** cs2cs
> cs2cs +proj=longlat +ellps=GRS80 +no_defs +to +proj=omerc +
> lat_0=4 +lonc=102.25 +alpha=323.0257964666666 +k=0.99984 +x_0=804671
> +y_0=0 +ell ps=GRS80 +units=m +no_uoff +rot_conv +no_defs
> 103.64025987222223 1.827764875
> 627096.13       202122.06 0.000
> 
> **gdal
> inn = inpGDM2000.ImportFromProj4("+proj=longlat +ellps=GRS80 +no_defs  <>");
> out = outRSO.ImportFromProj4("+proj=omerc +lat_0=4 +lonc=102.25
> +alpha=323.0257964666666 +k=0.99984 +x_0=804671 +y_0=0 +ellps=GRS80
> +units=m +no_uoff +rot_conv +no_defs <>")
> 959373.969 -240050.800
> 
> It looks that the +no_uoff +rot_conv is not used in the gdal enviroment

Bjørn,

If you add the +wktext flag to the string passed to ImportFromProj4(),
then the OGRSpatialReference code will capture a literal copy of
the PROJ.4 parameters in the internal representation.  I think you
will need this.

Normally the coordinate system is converted to an internal (OGC WKT)
representation which does not include exotic parameters such as
+no_uoff, and +rot_conv.

You would need at least GDAL/OGR 1.4.x for this feature.

Best regards,

-- 
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I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush    | President OSGeo, http://osgeo.org