[GRASSLIST:8902] Re: orthorectification of Quickbird satellite images

[Dan Gavin]

OK-I'll try i.points3 on GRASS 5, using the LANDSAT image option.  I 
will use some decent orthophotos in the target location to make the 
control points, and examine the quality of the result with stream and 
road vectors.  I may also compare it to Imagine or other software.  I 
don't have the data yet, but I'll report back with results in 
(hopefully) two weeks.

Dan


At 7:13 AM +0100 11/5/05, Markus Neteler wrote:
>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
>>  >
>>  >
>>  >-------------------------------------------------------------
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>
>  >
>
>--
>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
>Via Sommarive, 18        -       38050 Povo (Trento), Italy