[FWTools] warping of aster files

Frank Warmerdam fwarmerdam at gmail.com
Sun Jan 23 17:55:23 EST 2005

On Sun, 23 Jan 2005 15:30:41 +0100 (W. Europe Standard Time), Pål
Herman Sund <phsund at broadpark.no> wrote:
> On the other hand :
> 1. I know the coordinates of the 4 image corners and can read them to ASCIII
> files
> 2. I can compute these 4 corners with accurate transformation an present the
> result in ASCII files
> 3. I would like to warp the images with a transform (Helmert) based on the 4
> "GCP's)
> My questions would then be :-)
> 1. Is this possible ith FWTols "out-of the box" (he-he) ??
> 2. Could this be done by using the Python capabilities ??
> 3. Anyone who know software (preferrably open) which can do this
> out-of-the-box"


I'm not sure what you mean by a Helmert transform.  It is possible
to use gdal_translate to associate a set of GCPs with an image.  
Futhermore, gdalwarp can be used to rectify an image based
on the GCPs.  However, FWTools 0.9.4 only supports polynomial
warping based on GCPs.  0.9.4 will support thin plate splines too,
which might be more appropriate in this case. 

Assuming you get the version with thin plate spline transformations,
it should be pretty easy to script based on something invoking 
FWTools commandline programs.   That could be an awk script
driving things, or you could implement in Python if you wished. 

My suggestion would be to at least prototype it with what you have
now, and if you need the thin plate spline support just prod me a bit
till I issue FWTools 0.9.5 with that available. 

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    | Geospatial Programmer for Rent

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