[Proj] GTX format

Frank Warmerdam warmerdam at pobox.com
Sun Jan 8 13:37:25 EST 2012

On 12-01-08 01:49 AM, nicolas david wrote:

>     Is there something like geo2bin? To compile text data in binary format?
> I'm not aware of such utilities, for french geoidgrids I have to write my own
> utilitiy to convert from french geoid format to gtx format (you could look this
> code on gitorious
> http://gitorious.org/proj4-sandbox/proj4-cmake/blobs/ign/proj/src/ign2gtx.c )
> When your write "text data" do you mean like *.lla file ?

Michael / Nicolas,

I would add that GDAL now supports reading and writing GTX
files.  So you can use GDAL to translate from other formats
(ie. GeoTIFF, ASCII) to GTX.

Hmm, I was going to point off to the driver documentation but
it seems I haven't written any.  Perhaps I can do this today.

>     How to aware proj that new gtx file exists and where?
> A) add theses gtx files on your nad directory ( PROJ_LIB envVar)
> B) add the "+geoidgrids" option on your proj description

Right - they will only be used when the coordinate system
definitions include an explicit +geoidgrids directive.

Best regards,
I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
light and sound - activate the windows | http://pobox.com/warmerda
and watch the world go round - Rush    | Geospatial Software Developer

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