[gdal-dev] EPSG 8.0 Upgrade

[Jeremy Palmer]

Hi Frank,

Yes it would be great if grid shifts are supported in proj.4 by default, but for more importantly for us within Qgis. Currently I see QGIS builds it's CRS database using crssync which relies on GDAL OSRExportToProj4 for creating proj.4 strings. Does that mean that the gdal CSV files also need to support the grid shift? Before I raise any tickets it would be good to know where to actually fix the problem.

nzgd2kgrid0005.grd is the transformation between NZGD1949 and NZGD2000, not WGS84 and NZGD2000. See more information here http://www.linz.govt.nz/geodetic/software-downloads#distortiongrid. nzgd2kgrid0005.grd is created from the ASCII file which can be downloaded here http://www.linz.govt.nz/sites/default/files/geodetic/software-downloads/nzgd2kgrid9911.zip

Cheers,
Jeremy
 
________________________________________
From: fwarmerdam at gmail.com [fwarmerdam at gmail.com] On Behalf Of Frank Warmerdam [warmerdam at pobox.com]
Sent: Saturday, 8 December 2012 8:03 a.m.
To: Jeremy Palmer
Cc: gdal-dev; metacrs at lists.osgeo.org
Subject: Re: [gdal-dev] EPSG 8.0 Upgrade

Jeremy,

Unfortunately I do not automatically pickup references to grid shift files from the EPSG database.  To the extent these are supported it is accomplished by special hackery. In fact skimming the epsg file, I think the only datum for which grid shift files are used *by default* is NAD27.   Perhaps this would be a good time for me to review how to utilize at least the grid shift files we are distributing with PROJ.4 like ntf_r93.gsb and nzgd2kgrid0005.gsb.

Hmm, I am getting the impression that nzgd2kgrid0005.grd is actually the transformation between NZGD2000 and WGS84 and that we would actually need another file - possibly something like Nzgd49ToNzgd2K.gdc to support NZGD1949 - is that right?

I'd suggest you file a ticket in the PROJ.4 Trac on this issue with suggestions on how to proceed.

Best regards,
Frank



On Thu, Dec 6, 2012 at 10:12 AM, Jeremy Palmer <JPalmer at linz.govt.nz<mailto:JPalmer at linz.govt.nz>> wrote:
HI Frank,

Thanks that's great news. Has this upgrade now started supporting data shift grids, such as NZGD2000<->NZGD1949?

Cheers
Jeremy
________________________________________
From: gdal-dev-bounces at lists.osgeo.org<mailto:gdal-dev-bounces at lists.osgeo.org> [gdal-dev-bounces at lists.osgeo.org<mailto:gdal-dev-bounces at lists.osgeo.org>] On Behalf Of Frank Warmerdam [warmerdam at pobox.com<mailto:warmerdam at pobox.com>]
Sent: Thursday, 6 December 2012 1:18 p.m.
To: PROJ.4 and general Projections Discussions; GeoTIFF; gdal-dev; metacrs at lists.osgeo.org<mailto:metacrs at lists.osgeo.org>
Subject: [gdal-dev] EPSG 8.0 Upgrade

Folks,

At the request of Howard Butler, I have upgraded PROJ.4, libgeotiff, and
GDAL to use the EPSG 8.0 database in development "trunk".

This was accomplished, as usual based on the process described here:

   http://svn.osgeo.org/metacrs/geotiff/trunk/libgeotiff/csv/README

Amoung other things this will result in some datums having new preferred
datum shift solutions.  Upgrade with care.

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

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