| AVHRR Calibration and Georeferencing [message #69180] |
Sat, 19 December 2009 02:20  |
Susanne Adams
Messages: 1
Registered: December 2009
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Junior Member |
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Hi,
I have an AVHRR file that I want to first calibrate and then
georeference
using IDL (and ENVI).
Thanks to the 'envi_avhrr_calibrate_doit' I can input an AVHRR file
and
get it calibrated. The output of this function is a file of type ENVI.
Now, there is also an 'envi_avhrr_geometry_doit' function that does
what
georeferencing is needed, however, the input file to that function
must be
of type AVHRR.
The problem I'm facing is that I cannot input the file that I
calibrate
using the 'envi_avhrr_calibrate_doit' function (since it is of type
ENVI
and needs to be of type AVHRR).
I'd be grateful if someone could help me come up with a solution to
this
problem.
Susi
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| Re: AVHRR Calibration and Georeferencing [message #75509 is a reply to message #69180] |
Thu, 24 March 2011 10:11  |
Giuseppe Papa
Messages: 27
Registered: February 2010
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Junior Member |
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Hi Susi,
I had this exact same problem - And I'm sure you've probably already solved it by now but in case anyone else has the same problem here's how to solve it:
To both calibrate and navigate an AVHRR image in ENVI you have to first perform the calibration and save the result as an ENVI image (or to a file in ENVI's memory which is usually the handiest). Then you can georeference this calibrated ENVI image BUT you must give ENVI the original AVHRR image too.
In the dropdown menu to georeference (or warp) the calibrated image, select this image in memory first - the screen will refresh itself and you will be allowed to select the original AVHRR image secondly. ENVI will use the information from the original AVHRR image to further process your calibrated image.
I literally discovered this solution totally by accidentally, clicking on the wrong image when tired and sleepy. All the googling in the world couldn't give me this very simple solution - probably because it was too simple; but I'm self-taught in ENVI so it was anything but obvious to me :)
The procedure is the same if using ENVI in batch mode through IDL - calibrate first using envi_avhrr_calibrate_doit, then follow this up with:
"envi_doit, 'envi_avhrr_warp_doit', fid = (insert calibrated file fid), avhrr_fid = (orginial AVHRR fid), dims=dims, pos=pos" etc..
Hope this helps the next person who has this problem :)
Cheers,
Gillian
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