[gdal-dev] Coordinate Transformation problems

[Frank Warmerdam]

Christiaan Janssen wrote:
> I realize that PROJ.4's datum shift is only two dimensional with respect to
> a NAD27 to NAD83 shift but what this case is doing is really just a unit
> conversion. Both spatial reference systems are the same except for the
> linear unit, one is in feet the other meters. The conversion is resulting in
> the horizontal components being translated but the z component is left
> unchanged. Shouldn't it at least be converted to the appropriate units
> (1210ft -> 369m) to conform with the other two dimensions? Or is this
> something I will have to handle on my own?

Christiaan,

This would have to be handled by your own code.  The linear units is assumed
to apply only in the horizontal dimensions, not the vertical.  Generally
speaking GDAL/OGR is very weak on vertical coordinate system related
operations - a not uncommon issue in the GIS and remote sensing fields.

Best regards,
-- 
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