[gdal-dev] CTable2 documentation

[Erik Sørngård]

Hello Even,

Thank you clarifying that PROJ documentation is not accurate. I had seen the source code before, but was hoping for a supporting document as well.

Based on your input and looking at the source code again today, I expect the data to be stored as longitude and latitude offset pairs, each value being a 32 bit floating point number in radians, with east to west lines, from south to north.

Regards,
 
Erik Sørngård
R&D Manager
Gundersen & Løken AS
 
E: erik.sorngard at gl-instrumenter.no
P: +47 22 81 39 94

-----Original Message-----
From: Even Rouault [mailto:even.rouault at spatialys.com] 
Sent: Tuesday, June 19, 2018 6:14 PM
To: gdal-dev at lists.osgeo.org
Cc: Erik Sørngård <erik.sorngard at gl-instrumenter.no>
Subject: Re: [gdal-dev] CTable2 documentation

Erik,

> 
> I have been looking at PROJ's support for grid files, and notice that 
> they refer to "GDAL documentation" for format details about CTable2.
> 
> While browsing the GDAL site I have so far not been able to locate 
> this information, except for being part of the list of supported file formats:
> http://www.gdal.org/formats_list.html
> 
> Where can we find the CTable2 documentation?

That must be some developper sense of humour. To the best of my knowledge, the best documentation of the CTable2 format is the driver source code:

https://github.com/OSGeo/gdal/blob/master/gdal/frmts/raw/ctable2dataset.cpp

Basically there is a 160-byte header, followed by the longitude and latitude offsets, interleaved, and with south-to-north line ordering.

Even

--
Spatialys - Geospatial professional services http://www.spatialys.com