| Re: georeferencing satellite data [message #33084] |
Thu, 05 December 2002 14:08  |
Kelly Dean
Messages: 92
Registered: March 1997
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Member |
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Use IDL's Warp_Tri or Polywarp. I provide some tips on the CIRA IDL tips page.
http://www.cira.colostate.edu/special/csuidl/IDLremap0.htm
I use 25 latitude/longitude points over an image to georeference satellite imagery.
You only need four GCPs, but depending on the scene, more points helpout. 500 may be
to much. It takes seconds to run, where MAP_PATCH ( also a good IDL routine) will take
several minutes. For Map_Patch to work, you need to interpolate the 500 points to 5000
points.
For example
http://www.cira.colostate.edu/Special/CurrWx/hrpt/NLRGB.htm
However, if the 25 points do not fit on the image, you'll run into trouble. For
example:
http://www.cira.colostate.edu/Special/CurrWx/hrpt/NMRGB.htm
In this case, Map_Patch would have worked out better. However, Map_Patch requires a
lat/long value for each point.
Kelly Dean
CSU/CIRA
P.S. Check the CIRA site out quickly, I have been given my walking papers and the new
webmaster wants to eliminate my HTML work from the CIRA web server, which includes the
IDL tips and gallery.
Olivier ARCHER wrote:
> Hi,
> It might be a faq, but i'm in a hurry and didn't find it on google. so ...
>
> i'va got a satellite image, and i only got lat/lon for some points. I'd
> would like to get mlat and mlon to be array of the same dimensions of
> the image, containing interpolated lon/lat for each pixel of the image.
>
> so, my dream is:
> georef,image,lon,lat,x,y,mlon=mlon,mlat=mlat
> where image is the image (ie 5000x5000 array)
> lon lat are known position (ie 500 array)
> x and y are respective indice of lon/lat in the image (ie 500 array)
> mlon and mlat are output array for interpolated lon/lat (ie 5000x5000 array)
>
> map_path and map_image doesnt seem to be ok for me.
>
> If someone out there have a such routine ....
>
> Thanks
>
> --
> Olivier
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| Re: georeferencing satellite data [message #33085 is a reply to message #33084] |
Thu, 05 December 2002 12:42  |
dmarino
Messages: 9
Registered: November 2002
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Junior Member |
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Olivier-
I think you can set up an affine transform like so:
x' = Ax + By + C
y' = Dx + Ey + F
Where,
(x',y') = map location
(x ,y ) = column/row in pixels
A = x-scale : dimension of a pixel in X
B,D = rotation terms
E = negative of y-scale, pixel Y dimension
C,F = translation terms: x,y map coordinate
of the center of the upper-left pixel
You may have to do some calcs to get the upper left pixel center, but
if you have several points, you should be able to figure out the GSD
of those image pixels, and those things should get you there.
Sorry so brief, and good luck!
dmarino
Digitalglobe Inc
______________________
Olivier ARCHER <olivier.archer@ifremer.fr> wrote in message news:<3DED3365.8000701@ifremer.fr>...
> Hi,
> It might be a faq, but i'm in a hurry and didn't find it on google. so ...
>
>
> i'va got a satellite image, and i only got lat/lon for some points. I'd
> would like to get mlat and mlon to be array of the same dimensions of
> the image, containing interpolated lon/lat for each pixel of the image.
>
> so, my dream is:
> georef,image,lon,lat,x,y,mlon=mlon,mlat=mlat
> where image is the image (ie 5000x5000 array)
> lon lat are known position (ie 500 array)
> x and y are respective indice of lon/lat in the image (ie 500 array)
> mlon and mlat are output array for interpolated lon/lat (ie 5000x5000 array)
>
> map_path and map_image doesnt seem to be ok for me.
>
> If someone out there have a such routine ....
>
> Thanks
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| Re: georeferencing satellite data [message #33209 is a reply to message #33084] |
Wed, 11 December 2002 17:23 |
olivier.archer
Messages: 4
Registered: May 2000
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Junior Member |
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Kelly Dean wrote:
> Use IDL's Warp_Tri or Polywarp. I provide some tips on the CIRA IDL tips page.
>
> http://www.cira.colostate.edu/special/csuidl/IDLremap0.htm
>
>
> P.S. Check the CIRA site out quickly, I have been given my walking papers and the new
> webmaster wants to eliminate my HTML work from the CIRA web server, which includes the
> IDL tips and gallery.
>
>
>
Thanks Kelly,
it works nice, The real test will be done when i'll work over pole.
And what about your page at CIRA? it is usefull infomation ... the pages
will be moved or removed ? do i have to mirror then to have them in the
future ?
merci
--
Olivier
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