[GRASS5] Re: GDAL, GRASS and AVHRR

[Markus Neteler]

On Fri, Oct 11, 2002 at 10:27:10AM -0400, Helena Mitasova wrote:
> > > Ahh. We experienced this problem at PCI with some kinds of AVHRR data as
> > > well.  I believe our solution there was to add a "thin plate splines"
> > > transformation modelling in addition to the existing polynomial
> > > transformations.  This is a transform with as many terms as there are
> > > GCPs and gives increasing weight to gcps that are closer to the point
> > > being warped.  Almost a piecewise warp.>
> > > Implementing thin-plate splines, or some similar transformation
> > > mechanism is not trivial.  It also doesn't specifically belong in
> > > GDAL.>
> > > I would suggest that this issue be brought back to the GRASS dev list,
> > > and see if any of us can find a suitable source for a thin plate spline
> > > algorithm (or another with similar properties).  This could then
> > > be implemented in i.rectify or perhaps an i.rectify.tps.
> >
> > So: Is there anyone willing to help with extending i.rectify to
> > support also splines based rectification? Could we probably use functions
> > from src/libes/rst_gmsl/
> 
> I agree that it should be implemented in i.rectify. You sure can take
> advantage of rst_gmsl. There should be a paper by Fogl(?) from GISEM3
> conference in Santa Fe 1996 where he presented the rectification with a
> number of functions including RST (it was TPS then so many people refer to
> it thin plate spline) and RST performed really well. I will be happy to
> help, but you need to tell me where that interpolation/approximation needs
> to be applied as I am not familiar with i.rectify.
 
Thanks, Helena, for your offer. I'm also not too familiar with internals
of i.rectify.

It was David Fogel. His paper is here (thanks, google):
http://www.ncgia.ucsb.edu/conf/SANTA_FE_CD-ROM/sf_papers/fogel_david/santafe.html

Markus