| Looking for roll correction routine [message #28395] |
Wed, 05 December 2001 15:55 |
jmcfee
Messages: 17
Registered: August 1995
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Junior Member |
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Hi everyone,
I am trying to georegister some images taken by a line scanner from an aircraft.
The raw images have a considerable roll component and, unfortunately, no roll
information was recorded. There are a (very) few ground control points (GCPs) in
the image. I tried georegistering the image using the GCPs and the Map -->
Registration --> "Warp from GCPs: image to map" function of ENVI. The results
were not too good. This is partly because the roll is not slow. It appears to
change significantly over a few lines, whereas the few control points are spaced
many lines apart. It seems that I have to do a roll correction first before the
registration.
Fortunately, there is a very straight road running the length of the image
(that's why I know the roll is so significant). I was planning to do the roll
correction by:
1. one line at a time (or more likely a few lines at a time) -
a. detect one edge of the road
b. shift each line to align the current road edge pixels with the edge
position of the previously corrected line or group of lines
2. do a standard ENVI georegistration on the roll corrected image.
I think I could write the roll correction portion in IDL. It's fairly straight
forward, although not trivial. I think it would take a moderate amount of time
and then I'd have to debug it. However, this must be a fairly common problem and
I would assume that someone has already written such a routine.
If anyone knows where I could find one in IDL, C, MATLAB or any high level
language, I would greatly appreciate it.
Many thanks in advance
John McFee
--
Dr. John E. McFee
Defence Research Establishment Suffield
Box 4000, Medicine Hat, AB Canada T1A 8K6
(403) 544-4739 (voice) 544-4704 (fax)
e-mail: John.McFee@dres.dnd.ca
--
____________
Dr. John E. McFee | John.McFee@dres.dnd.ca
Head Threat Detection Group | www.dres.dnd.ca, www.ccmat.gc.ca
Defence Research Establishment Suffield | PH: 403-544-4739
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