[gdal-dev] Custom vertical transformations

[Even Rouault]

Kristian,

https://github.com/OSGeo/gdal/pull/4639 will allow you to use an 
arbitrary pipeline to do a vertical transformation through gdalwarp

Even

Le 23/08/2021 à 10:50, Kristian Evers a écrit :
> Thanks for your insights, Even! I had a feeling I was pushing the boundaries here, good to get that confirmed.
>
> The idea of using -s_srs and a correction grid is intriguing. I assume this way will be easier to implement as well since I don't have to worry as much about the CRS and extent of my correction grid as when using gdal_calc. The correction grids I already have are in EPSG:4326 and I assume GDAL is clever enough to handle that or at least pass the responsibility over to PROJ. I'll try a few things and report back how it goes.
>
> I'll make sure to add a ticket for extending the scope of gdalwarp to the 3D-space.
>
> /Kristian
>
>> -----Original Message-----
>> From: Even Rouault <even.rouault at spatialys.com>
>> Sent: 20. august 2021 17:30
>> To: Kristian Evers <kreve at sdfe.dk>; gdal-dev at lists.osgeo.org
>> Subject: Re: [gdal-dev] Custom vertical transformations
>>
>>
>>> Regarding your immediate issue, the workaround I see would be that you
>>> use PROJ to create a regular grid that contains the vertical
>>> correction, use gdalwarp to transform it to the exact extent and
>>> resolution of the result of your 2D-only gdalwarp, and finally use
>>> gdal_calc to sum the two.
>>>
>> Well, if you actually create a vertical correction only grid, then you
>> could just use  -s_srs "+proj=longlat +ellps=...
>> +geoidgrids=your_tif_or_gtx"  (or maybe as output, or fix the sign of
>> the correction in the grid), since the workaround I give above is what
>> gdalwarp would do. But of course none of this will solve the
>> time-dependent aspect you need.
>>
>> --
>>
>> http://www.spatialys.com
>> My software is free, but my time generally not.

-- 
http://www.spatialys.com
My software is free, but my time generally not.