[gdal-dev] RFC 22: RPC Georeferencing

[Brent Fraser]

Frank,

  Would this implementation include using a DEM for height information
when transforming the locations, or only a constant height?

Best Regards,
Brent Fraser

>
> Folks,
>
> It is proposed that GDAL support an additional mechanism for geolocation
> of
> imagery based on rational polynomial coefficients (RPCs) represented as
> metadata.
>
> Many modern raw satellite products are distributed with RPCs, including
> products from GeoEye, and DigitalGlobe. RPCs provide a higher systematic
> description of georeferencing over an image, and also contain information
> on
> the viewing geometry that in theory makes orthocorrection (given a DEM)
> and
> some 3D operations like building height computation possible.
>
> To some extent RPCs were already supported in GDAL but the support was
> incomplete and not well documented.  This RFC revises the approach
> somewhat
> and is intended to make this a "fully supported" geolocation method in
> GDAL.
>
>    http://trac.osgeo.org/gdal/wiki/rfc22_rpc
>
> Pretty much everything is already implemented and committed, but I'm
> willing
> to make changes as needed.  One aspect that I consider very unsettled (and
> which I have not yet committed) is the SWIG bindings for the GDAL
> transformer
> API.  I'd especially appreciate if the SWIG gods could review and propose
> a
> better binding approach.  The current bindings result in code like this:
>
>      ds = gdal.Open('data/gcps.vrt')
>      tr = gdal.Transformer( ds, None, [ 'METHOD=GCP_POLYNOMIAL' ] )
>
>      (success,pnt) = tr.TransformPoint( 0, 20, 10, 0 )
>
> With "pnt" being a 3-tuple.  I don't even see how the TransformPoints
> function in the proposal (transform an array of points in place) will
> map in Python.
>
> This email is a call for feedback, but I'm hoping to put forward a motion
> to adopt on Monday sometime, so prompt feedback for revisions is
> encouraged!
>
> Best regards,
> --
> ---------------------------------------+--------------------------------------
> I set the clouds in motion - turn up   | Frank Warmerdam,
> warmerdam at pobox.com
> light and sound - activate the windows | http://pobox.com/~warmerdam
> and watch the world go round - Rush    | President OSGeo, http://osgeo.org
>
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