[gdal-dev] Transforming Raster Points from GeoTIFF with GCPs

[Simon Eves]

Aha! That's the bit I hadn't found. Thank you! :)

On Fri, Dec 10, 2021 at 10:38 AM Yann-Sebastien Tremblay-Johnston <
yanns.tremblay at gmail.com> wrote:

> Simon,
>
> See the Transformer API, in particular
> https://gdal.org/api/gdal_alg.html?highlight=transformer#_CPPv419GDALTransformerFunc
> (or gdal.Transformer in Python).
>
> Sebastien
>
> On Fri, Dec 10, 2021 at 10:24 AM Simon Eves <simon.eves at omnisci.com>
> wrote:
>
>> So we have a GeoTiFF of Sentinel-1 imagery which `gdalinfo` reports as
>> having a GCP projection with 210 points, which we'd (perhaps naively?!)
>> like to import directly, transforming to WGS84 on the fly.
>>
>> Obviously a simple OGRSpatialReference/OGRCoordinateTransformation
>> transform isn't going to do anything, so I assume we have to do the GCP
>> transform manually.
>>
>> I found the GCPCoordinateTransformation class and other supporting code
>> in ogr2ogr_lib.cpp as used by gdaltransform, which seems to do what we
>> need, but of course it's not in the core GDAL library so we can't "just use
>> it".
>>
>> Before embarking on lifting out that code to implement an on-the-fly
>> transformer in our system, I just wanted to make sure I wasn't missing any
>> functionality elsewhere that would make it easier.
>>
>> It may also be more efficient to just kick off a gdalwarp to pre-convert
>> the file so we can just import it with no transformation required, but that
>> seems ugly unless it's gonna be WAY more efficient?
>>
>> Thanks,
>>
>> Simon
>>
>> --
>> <http://www.omnisci.com/>
>> Simon Eves
>> Senior Graphics Engineer, Rendering Group
>> 100 Montgomery St (5th Floor), San Francisco, CA 94104, USA
>>
>>
>> Email: simon.eves at omnisci.com | Cell:  +1 (415) 902-1996
>>
>> _______________________________________________
>> gdal-dev mailing list
>> gdal-dev at lists.osgeo.org
>> https://lists.osgeo.org/mailman/listinfo/gdal-dev
>>
>

-- 
<http://www.omnisci.com/>
Simon Eves
Senior Graphics Engineer, Rendering Group
100 Montgomery St (5th Floor), San Francisco, CA 94104, USA


Email: simon.eves at omnisci.com | Cell:  +1 (415) 902-1996
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.osgeo.org/pipermail/gdal-dev/attachments/20211210/72cf555f/attachment-0001.html>