[gdal-dev] OGR/PROJ with +geoidgrids

Ben Discoe ben at vterrain.org
Tue Aug 16 21:24:58 EDT 2011

It is true that geocentric XYZ coordinates are not very useful, without being able to convert them to coordinate with orthometric ("geoid") ("sea level") height.

Frank implemented 'preliminary' support for this, which i am preparing to test now.  Before expecting it to work in GDAL/OGR, i thought i should try it down in PROJ.4 first, following the description on http://trac.osgeo.org/proj/wiki/VerticalDatums

If i try a point near me in California, it works regularly:

cs2cs +proj=latlong +datum=WGS84 +to +proj=utm +zone=10 +datum=WGS84
-122.272778 37.871667 10
563959.68       4191825.55 10.00

But if i try to provide a geoid file (from http://download.osgeo.org/proj/vdatum/usa_geoid2009.zip) then it seems to not work:

cs2cs +proj=latlong +datum=WGS84 +to +proj=utm +zone=10 +datum=WGS84 +geoidgrids=g2009conus.gtx
-122.272778 37.871667 10
Rel. 4.7.1, 23 September 2009
<cs2cs>: while processing file: <stdin>, line 1
pj_transform(): Unknown error
*       * 10.00

The goal is to transform the input elevation (10 meters, ellipsoidal height, i presume) to an orthometric height (which will use the geoid, i presume).

Maybe i'm doing it wrong?


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