[GRASSLIST:8904] Re: orthorectification of Quickbird satellite images

[Michael Barton]

If I remember correctly, i.points3 works fine in GRASS 5.
...but i.rectify3 does not. And you must have i.rectify3 to actually do the
rectification of the GCP's created in i.points3.

The main difference between i.points3 and i.points that I remember is that
i.points3 can use both raster and vector maps as a backdrop for
rectification. I.points uses raster maps only and i.vpoints uses vector maps
only. 

I.points3 creates a text file of GCP's like i.points, BUT it does it with a
different format. Hence it requires i.rectify3 to use the data it creates.

Michael
__________________________________________
Michael Barton, Professor of Anthropology
School of Human Evolution and Social Change
Arizona State University
Tempe, AZ 85287-2402

phone: 480-965-6213
fax: 480-965-7671
www: http://www.public.asu.edu/~cmbarton



> From: Dan Gavin <dgavin at uvm.edu>
> Date: Sat, 5 Nov 2005 08:44:36 -0500
> To: Markus Neteler <neteler at itc.it>
> Cc: <GRASSLIST at baylor.edu>
> Subject: [GRASSLIST:8902] Re: orthorectification of Quickbird satellite images
> 
> 
> 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