[Proj] converting WGS84/ETRS89 to ITM/OSGM15

Elmir Jagudin elmir.jagudin at gmail.com
Mon Sep 3 05:15:37 EST 2018

On Thu, Aug 23, 2018 at 10:41 AM Elmir Jagudin <elmir.jagudin at gmail.com>

> On Wed, Aug 22, 2018 at 12:12 PM Alain Orsoni <Alain.Orsoni at ign.fr> wrote:
>> Hi,
>> Trying to answer with my knowledge :
>> On my computer I can do this transform in this way
>> echo -6.6 53 21 | cs2cs +init=epsg:4326 +to +proj=tmerc +lat_0=53.5
>> +lon_0=-8 +k=0.99982 +x_0=600000 +y_0=750000 +ellps=GRS80
>> +towgs84=0,0,0,0,0,0,0 +geoidgrids=egm08_25_rg.gtx +units=m +no_defs
>> 693972.63 695281.52 -35.37
>> The result is a little bit different from what you expect. Maybe because
>> I use egm08 and you expect another Geoid model.
> Aha, cool. This looks like the right path for me.
> Yes, the OSGM15 is probably using slightly different geoid model. I'll try
> to create gtx file for OSGM15.

After creating a GTX table for OSGM15, the height calculations look
correct. Thanks for help Alain and Even!

Is it possible to contribute these GTX files, so they are included into
future proj4 releases?
Should I make a PR to this repo: https://github.com/OSGeo/proj-datumgrid ?

The tables are here for now:

Best Regards,
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