[GRASSLIST:8899] Re: orthorectification of Quickbird satellite images

[Markus Neteler]

On Fri, Nov 04, 2005 at 11:40:59PM -0500, Dan Gavin wrote:
> Ian,
> Thanks for the comment.  My reading and experience with i.points and 
> i.rectify is that is does a rectification for planar surfaces, but 
> can't take terrain displacement into account.  i.ortho.photo does use 
> a DEM in conjunction with rectification, but it is tailored to aerial 
> photos, not satellite images.  Low elevation satellite images (> 20 
> degrees from nadir) accentuate the effect of topography.

Right - i.points and i.rectify are not suitable to make an 
*ortho*rectification of satellite data, nor i.ortho.photo.
Not sure if i.points3/i.rectify3 were ever functional. I have seen
a model at least for LANDSAT orthorectification in the underlying
library image3.

Dan, do you see a change to test this in the older GRASS 5?
If (almost) successful, we can think about porting it to GRASS 6.

Markus


> Dan
> 
> At 5:20 PM -0800 11/4/05, Ian MacMillan wrote:
> >Dan, I am not sure about i.points3, but i.points and i.rectify does 
> >work.  I think you will still need a higher resolution DEM for your 
> >elevation correction (depending on the resolution you want for your 
> >satellite imagery).  Those are sometimes hard to obtain for large 
> >parts of the world.
> >
> >Hope this helps,
> >Ian
> >
> >
> >On Nov 4, 2005, at 3:42 PM, Dan Gavin wrote:
> >
> >>
> >>Hello all:
> >>
> >>I would like to orthorectify some high-resolution Quickbird images, 
> >>taken 20 degrees off-nadir.  They are in a mountainous region, and 
> >>I need fairly high positional accuracy.  While these images are 
> >>distributed as geoTIFFs, elevational distortions have not been 
> >>removed (their ortho product is based on a 90 meter DEM). 
> >>Searching the list archives, I see a suggestion to use i.points3 
> >>and i.rectify3.  Are these functions available in GRASS 6.1?  Any 
> >>other suggestions, including other software?
> >>
> >>Many thanks,
> >>
> >>Dan
> >>
> >>--
> >>Dan Gavin
> >>Research Associate
> >>University of Vermont
> >>Botany and Agricultural Biochemistry
> >>120B Marsh Life Science
> >>109 Carrigan Dr.
> >>Burlington, VT 05405-0086
> >>
> > >
> >>
> >What happens if a big asteroid hits Earth? Judging from realistic 
> >simulations involving a sledge hammer and a common laboratory frog, 
> >we can assume it will be pretty bad.
> > - Dave Barry
> >
> >
> >-------------------------------------------------------------
> >This message has been scanned by Postini anti-virus software.
> 
> 
> -- 
> Dan Gavin
> Research Associate
> University of Vermont
> Botany and Agricultural Biochemistry
> 120B Marsh Life Science
> 109 Carrigan Dr.
> Burlington, VT 05405-0086
> 

-- 
Markus Neteler     <neteler itc it>       http://mpa.itc.it
ITC-irst -  Centro per la Ricerca Scientifica e Tecnologica
MPBA - Predictive Models for Biol. & Environ. Data Analysis
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