[GRASSLIST:8902] Re: orthorectification of Quickbird
satellite images
Dan Gavin
dgavin at uvm.edu
Sat Nov 5 08:44:36 EST 2005
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
>> >
>> >
>> >-------------------------------------------------------------
> > >This message has been scanned by Postini anti-virus software.
>
> >
>
>--
>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
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