| 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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