[gdal-dev] RPC to geotransform converting

[Denis Rykov]

Hi,

I have a GeoTIF file and file with RPC information next to it (*.txt). Is
there a way to transform this raster to a normal geotiff without
displacement (with geotransform inside) or is it fundamentally impossible?
I've tried to achieve it with gdalwarp but in this case the result of the
transformation has about 5 meters (10 pixels) x-displacement (I use QGIS to
visualize it).

Denis

[Even Rouault]

Denis,

if the view angle is off-nadir, you generally need to use the -to
RPC_DEM= option with a DEM covering the area of interest (and make sure
the values it contains are WGS 84 ellipsoidal elevations) to get
accurate results.

Even

Post by Denis Rykov
Hi,
I have a GeoTIF file and file with RPC information next to it (*.txt).
Is there a way to transform this raster to a normal geotiff without
displacement (with geotransform inside) or is it fundamentally impossible?
I've tried to achieve it with gdalwarp but in this case the result of
the transformation has about 5 meters (10 pixels) x-displacement (I
use QGIS to visualize it).
Denis
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gdal-dev mailing list
https://lists.osgeo.org/mailman/listinfo/gdal-dev

[Denis Rykov]

Thanks!

Post by Even Rouault
Denis,
if the view angle is off-nadir, you generally need to use the -to RPC_DEM=
option with a DEM covering the area of interest (and make sure the values
it contains are WGS 84 ellipsoidal elevations) to get accurate results.
Even
Hi,
I have a GeoTIF file and file with RPC information next to it (*.txt). Is
there a way to transform this raster to a normal geotiff without
displacement (with geotransform inside) or is it fundamentally impossible?
I've tried to achieve it with gdalwarp but in this case the result of the
transformation has about 5 meters (10 pixels) x-displacement (I use QGIS to
visualize it).
Denis
_______________________________________________
-- http://www.spatialys.com
My software is free, but my time generally not.

[Denis Rykov]

Finally I solved the issue by adding "-to RPC_HEIGHT=XXX" to gdalwarp.
It seems gdalwarp doesn't take this parameter into account even if it is
presented in the RPC *.txt file.
Should I file the ticket or was it done by purpose?

Post by Denis Rykov
Thanks!

Post by Even Rouault
Denis,
if the view angle is off-nadir, you generally need to use the -to
RPC_DEM= option with a DEM covering the area of interest (and make sure the
values it contains are WGS 84 ellipsoidal elevations) to get accurate
results.
Even
Hi,
I have a GeoTIF file and file with RPC information next to it (*.txt). Is
there a way to transform this raster to a normal geotiff without
displacement (with geotransform inside) or is it fundamentally impossible?
I've tried to achieve it with gdalwarp but in this case the result of the
transformation has about 5 meters (10 pixels) x-displacement (I use QGIS to
visualize it).
Denis
_______________________________________________
-- http://www.spatialys.com
My software is free, but my time generally not.

[Even Rouault]

You mean the HEIGHT_OFFSET parameter in the RPC ? Yes, that can
generally be used as a first-order correction if you don't use a DEM.
I'm not sure using it vs not-using it has been a deliberate choice. One
could say that with the current behavior people know that something is
wrong and must thus set something additional. There was a related
discussion in https://github.com/qgis/QGIS/pull/36385. A non breaking
change would be to make -to RPC_HEIGHT=HEIGHT_OFFSET work

Post by Denis Rykov
Finally I solved the issue by adding "-to RPC_HEIGHT=XXX" to gdalwarp.
It seems gdalwarp doesn't take this parameter into account even if it
is presented in the RPC *.txt file.
Should I file the ticket or was it done by purpose?
Thanks!
On Tue, May 18, 2021 at 10:57 PM Even Rouault
Denis,
if the view angle is off-nadir, you generally need to use the
-to RPC_DEM= option with a DEM covering the area of interest
(and make sure the values it contains are WGS 84 ellipsoidal
elevations) to get accurate results.
Even

Post by Denis Rykov
Hi,
I have a GeoTIF file and file with RPC information next to it
(*.txt). Is there a way to transform this raster to a normal
geotiff without displacement (with geotransform inside) or is
it fundamentally impossible?
I've tried to achieve it with gdalwarp but in this case the
result of the transformation has about 5 meters (10 pixels)
x-displacement (I use QGIS to visualize it).
Denis
_______________________________________________
gdal-dev mailing list
https://lists.osgeo.org/mailman/listinfo/gdal-dev <https://lists.osgeo.org/mailman/listinfo/gdal-dev>

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