why does it cost so much time for finding the matching points?(registration)

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why does it cost so much time for finding the matching points?(registration)

hcliu-2
When I use "correl" to find matching points in two satellite image, it nearly costs 30 minutes. I want to konw that in which part of the algorithm  that cost so much time , and how to improve it ?     Thank you very much for answering !

       

 

        hcliu
        [hidden email]
          2008-11-04
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Re: why does it cost so much time for finding the matching points?(registration)

Hernán De Angelis
Hi,

I guess there are many possible explanations for that, the most likely
is that you are not choosing good values of minimum correlation
coefficient (-c) or corner density (-d). Others may be: slow computer,
big images, images with different resolution, images covering
different regions, images taken at different seasons/times and
therefore radiometrically different or any combination of those.

good luck


Hernán



2008/11/4 hcliu <[hidden email]>:

> When I use "correl" to find matching points in two satellite image, it nearly costs 30 minutes. I want to konw that in which part of the algorithm  that cost so much time , and how to improve it ?     Thank you very much for answering !
>
>
>
>
>
> hcliu
> [hidden email]
> 2008-11-04
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--

Hernán De Angelis
Linux user # 397217

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Re: why does it cost so much time for finding the matchingpoints?(registration)

Frederic Claudel

hcliu,
here are a few tips, but it's been a long time since I worked with correl :
- is the intersection of the images small relatively to the largest image
footprint? correl limits the search area to that intersection, but there
used to be a bug inducing a bad intersection actually If I remember well, it
was the full size of the reference image) , thus a very large search area =>
very slow
- have you built the image pyramids (overviews) before uisng correl? If you
work at non-full resolution for any of the images, I advise you to do so.
- the corner density : use  avery low density, but correl works per image
tile, and always uses at least 1 point per tile. So you always end up having
a large number of matching points =>you might try to increase the image tile
size.

waht kind of images are you using?

regards,
Frederic

-----Message d'origine-----
De : Hernán De Angelis [mailto:[hidden email]]
Envoyé : mardi 4 novembre 2008 12:22
À : hcliu
Cc : ossim-developer
Objet : Re: [OSSIM] why does it cost so much time for finding the
matchingpoints?(registration)

Hi,

I guess there are many possible explanations for that, the most likely is
that you are not choosing good values of minimum correlation coefficient
(-c) or corner density (-d). Others may be: slow computer, big images,
images with different resolution, images covering different regions, images
taken at different seasons/times and therefore radiometrically different or
any combination of those.

good luck


Hernán



2008/11/4 hcliu <[hidden email]>:
> When I use "correl" to find matching points in two satellite image, it
nearly costs 30 minutes. I want to konw that in which part of the algorithm
that cost so much time , and how to improve it ?     Thank you very much for
answering !

>
>
>
>
>
> hcliu
> [hidden email]
> 2008-11-04
> ----------------------------------------------------------------------
> --- This SF.Net email is sponsored by the Moblin Your Move Developer's
> challenge Build the coolest Linux based applications with Moblin SDK &
> win great prizes Grand prize is a trip for two to an Open Source event
> anywhere in the world
> http://moblin-contest.org/redirect.php?banner_id=100&url=/
> _______________________________________________
> www.ossim.org
> Ossim-developer mailing list
> [hidden email]
> https://lists.sourceforge.net/lists/listinfo/ossim-developer
>



--

Hernán De Angelis
Linux user # 397217

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