[gdal-dev] OGR/PROJ with +geoidgrids

[Ben Discoe]

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?

Thanks,
Ben