[gdal-dev] Specify Grid Rotation for gdal.Warp() with Geolocation Arrays

Thu Nov 17 07:11:36 PST 2022

This may be a helpful resource: https://github.com/rasterio/affine

On Thu, Nov 17, 2022, 9:08 AM Even Rouault <even.rouault at spatialys.com>
wrote:

>
> Le 17/11/2022 à 16:01, Brendan Heberlein a écrit :
>
> Thank you, Mike & Even.
>
> Supposing I wanted to have the output grid origin & dimensions computed
> automatically, but with a specified rotation angle, is that possible?
>
> There's no API in GDAL for it. You indeed have to set something like the
> following
>
>
> gt[1] = cos(angle) * pixel_x_size
>
> gt[2] = -sin(angle) * pixel_x_size
>
> gt[4] = sin(angle) * pixel_y_size
>
> gt[5] = cos(angle) * pixel_y_size
>
>
> I assume the above only works if the origin (gt[0], gt[3]) is the
> lower-left corner coordinate, not the upper-one. And I might certainly have
> got some signs wrong :-)
>
>
> Slightly related code in the ENVI driver to transform the rotation angle
> from its header file to a geotransform matrix (but conventions might be
> slightly different):
>
>
> https://github.com/OSGeo/gdal/blob/66d9fe0b1a34a8992c804c2444f7f23c2436b937/frmts/raw/envidataset.cpp#L1536
>
>
> Anyway I can calculate these parameters myself, so it is not a big issue.
> Your suggestion worked for me.
>
> Cheers!
> Brendan
>
> ------------------------------
> *From:* Even Rouault <even.rouault at spatialys.com>
> <even.rouault at spatialys.com>
> *Sent:* Saturday, November 5, 2022 4:36 AM
> *To:* Michael Sumner <mdsumner at gmail.com> <mdsumner at gmail.com>; Brendan
> Heberlein <bheberlein at wisc.edu> <bheberlein at wisc.edu>
> *Cc:* gdal-dev <gdal-dev at lists.osgeo.org> <gdal-dev at lists.osgeo.org>
> *Subject:* Re: [gdal-dev] Specify Grid Rotation for gdal.Warp() with
> Geolocation Arrays
>
>
>
> Le 05/11/2022 à 04:33, Michael Sumner a écrit :
>
> yes I see, well you can probably set a target GeoTIFF with the
> geotransform that you want - and gdalwarp to that as the target.
>
> something like
>
> out_ds = gdal.GetDriverByName("GTiff").Create("output.tif", width, height,
> number_of_bands, data_type, options = ["TILED=YES"])
>
> out_ds.SetGeoTransform([ some geotransform with rotational terms ])
>
> srs = osr.SpatialReference()
>
> srs.ImportFromEPSG( xxx ) / srs.ImportFromWkt( xxx )
>
> out_ds.SetSpatialRef( srs )
> gdal.Warp(out_ds, src_ds, .... )
>
>
>
> I don't believe you can do that with gdalwarp directly, and I have no idea
> with python - and finally I'm sorry to add irrelevant discussion - but this
> is interesting and I'm going to try it out in R and C++ and would love to
> see a python example too.
>
> Cheers, Mike
>
>
>
>
>
> On Sat, Nov 5, 2022 at 2:21 PM Brendan Heberlein <bheberlein at wisc.edu>
> wrote:
>
> Hi Mike,
>
> regardless of the map projection, it may be desirable to have the grid
> oriented in one direction or another, e.g. due to the spatial distribution
> of data points. Although the CRS/SRS designates the coordinate axes, these
> are not always aligned with the desired grid orientation.
>
> So, basically I want to be able to specify an arbitrary geotransform array
> for the output grid. This would allow the grid to be assigned an arbitrary
> orientation within the CRS frame.
>
> Thanks,
> Brendan
> ------------------------------
> *From:* Michael Sumner <mdsumner at gmail.com>
> *Sent:* Friday, November 4, 2022 6:57 PM
> *To:* Brendan Heberlein <bheberlein at wisc.edu>
> *Cc:* gdal-dev <gdal-dev at lists.osgeo.org>
> *Subject:* Re: [gdal-dev] Specify Grid Rotation for gdal.Warp() with
> Geolocation Arrays
>
> well, the map projection does this - there are many possibilities. Or, do
> you have another geolocation array you want as the target?
>
> If you have an example I'm happy to try a few things, but I'd assumed you
> had a target map projection in mind. What kind of crs to choose depends on
> your goal, or is purely to not have north up?
>
> Perhaps there's something terminology wise I'm missing ...
>
> Mike
>
> On Sat, 5 Nov 2022, 10:50 Brendan Heberlein, <bheberlein at wisc.edu> wrote:
>
> Hi Mike,
>
> thanks for the response.
>
> Can you clarify how I would go about specifying the grid orientation for
> the output raster? None of -te, -ts or -t_srs address this.
>
>
> ------------------------------
> *From:* Michael Sumner <mdsumner at gmail.com>
> *Sent:* Friday, November 4, 2022 6:41 PM
> *To:* Brendan Heberlein <bheberlein at wisc.edu>
> *Cc:* gdal-dev <gdal-dev at lists.osgeo.org>
> *Subject:* Re: [gdal-dev] Specify Grid Rotation for gdal.Warp() with
> Geolocation Arrays
>
> that's exactly what the warper does with geolocation arrays, set the
> target extent, dimension, and crs with -te, -ts, -t_srs with gdalwarp.
>
> python will have those analogous controls for the warper.
>
> Cheers, Mike
>
>
>
> On Sat, 5 Nov 2022, 01:23 Brendan Heberlein via gdal-dev, <
> gdal-dev at lists.osgeo.org> wrote:
>
> Hello,
>
> I would like to be able to warp an image dataset using a geolocation
> array, while specifying the grid to which the output dataset is sampled.
> Specifically, I want to be able to warp the dataset to a grid which is not
> oriented North-up.
>
> Can GDAL support this currently? Or, what is the likelihood this could be
> supported in the future?
>
> I primarily rely on the Python bindings, so a solution within that
> framework would be ideal for me.
>
> Thanks!
>      — Brendan
>
>
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>
>
>
> --
> Michael Sumner
> Software and Database Engineer
> Australian Antarctic Division
> Hobart, Australia
> e-mail: mdsumner at gmail.com
>
> _______________________________________________
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>
> -- 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.
>
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