[GRASS-user] help on imge registration

GRASS GRASS user
1

I' quite a novice user of Grass and trying to use it for a non conventional task:

I need to register a series of images of an almost planar object to find out modification.
I' ve decided to use Grass in the following way:

1) take one of the images that has metric references , using i.points I set up a sereies of reference points on the image and then I use i.rectify wint secon order polinomial to warp the image ino a "rectiied, metric one"
    (the coord system is XY, planar)

2) for all the other images, I use i.points on the rectified image

Now the questions:

1) are i.rectify and i.point able to handle homographies?
I' ve found a nice reference paper on http://gisws.media.osaka-cu.ac.jp/grass04/viewpaper.php?id=37
but I did not fund anything in grass62 neither browsing thru CVS.
Are these modules needed to handle homographies transforms ?

2) there are also other modules like photo.camera photo.2image photo.2target photo.rectify I did not used them because they reqired camera parameters I do not have.
Are they able to handle homographies?

Thanks in advance
                                Luigi

2

Luigi Calori wrote:

Now the questions:

1) are i.rectify and i.point able to handle homographies?

No, they don't.

Luigi Calori wrote:

I' ve found a nice reference paper on
http://gisws.media.osaka-cu.ac.jp/grass04/viewpaper.php?id=37
but I did not fund anything in grass62 neither browsing thru CVS.
Are these modules needed to handle homographies transforms ?

Yes. They have been integrated into i.points.auto:
http://grass.gdf-hannover.de/wiki/Image_processing
-> download link

Note that the code needs an update to GRASS 6 (most is
based on 2 master theses at ITC-irst).

Luigi Calori wrote:

2) there are also other modules like photo.camera photo.2image
photo.2target photo.rectify I did not used them because they reqired
camera parameters I do not have.
Are they able to handle homographies?

No, they handle central projection (as needed for ortho-rectification
of aerial images).

Best
Markus
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3

Markus Neteler wrote:

----

Yes. They have been integrated into i.points.auto:
http://grass.gdf-hannover.de/wiki/Image_processing
-> download link

Note that the code needs an update to GRASS 6 (most is
based on 2 master theses at ITC-irst).

Thanks for the hint, I downloaded it, got grass 6.2.2 src, compiled on
my kubuntu and got it working.
I was able to specify matching lines and the module added some lines
to point list file in the image group with a new tag (2?) instead of 1.

My question is, how I use this info? Do I need another module like
i.homography (that I did not find out?) or is the standard module
i.rectify able to compute and apply the homographies using these special
format lines?

I also tried to use the semi automatic and automatic match poitns
feature but I did not understand how to use it.
Is this sw the same as referred in the article

http://gisws.media.osaka-cu.ac.jp/grass04/viewpaper.php?id=37

or something different?

Thanks again
                Luigi

4

Luigi,

you are right, I was confused: we have two modules.
I have added them now to the GRASS Addons SVN and updated
the links at
  http://grass.gdf-hannover.de/wiki/Image_processing#Geocoding

The i.homography appears to be based still on GRASS 5 (so updated needed).
The MSc theses (laurea) are probably available from University of Trento
or maybe we have the PDF files (write me offlist if you are interested).

Hope this (somewhat) helps,
Markus

Luigi Calori wrote:

Markus Neteler wrote:

----

Yes. They have been integrated into i.points.auto:
http://grass.gdf-hannover.de/wiki/Image_processing
-> download link

Note that the code needs an update to GRASS 6 (most is
based on 2 master theses at ITC-irst).

Thanks for the hint, I downloaded it, got grass 6.2.2 src, compiled on
my kubuntu and got it working.
I was able to specify matching lines and the module added some lines
to point list file in the image group with a new tag (2?) instead of 1.

My question is, how I use this info? Do I need another module like
i.homography (that I did not find out?) or is the standard module
i.rectify able to compute and apply the homographies using these special
format lines?

I also tried to use the semi automatic and automatic match poitns
feature but I did not understand how to use it.
Is this sw the same as referred in the article

http://gisws.media.osaka-cu.ac.jp/grass04/viewpaper.php?id=37

or something different?

Thanks again
                Luigi

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