From: Steve Joyce <address@hidden>
To: address@hidden
Sent: Fri, 9 October, 2009 7:56:56 PM
Subject: Re: [Paparazzi-devel] Photogrammetry (was georeferencing video
stream)
You know for relatively flat areas is might not be so bad at all if you are careful to synchronize your attitude data with the video frames.
What I would do is start with trying to project video frames on to a flat plane at ground level. There is no need to mix in GRASS or other software, everything you need is in the OpenCV library (although it might not be obvious at first), including processing video sequences. See cvWarpPerspective().
I think the biggest error you will have will be in yaw. In the abscence of a compass, you can only infer the yaw angle from the GPS heading and the current wind estimate. You can try to extract some keypoints from the video frames and match keypoints between frames to adjust the angles. I think there is a demo progam in OpenCV that tracks keypoints in video sequences (blobtrack?).
You were pretty close with your plan you wrote a few days ago except you
don't actually have to rectify the entire image until you want to produce a final result. All the calcualtions are done with the orientation data and tie point cloud.
[*A] is a projection from image coordinates to object coordinates. See cvProjectPoints2(), then realize it is backwards, but the equations are well known.
[*B] is essentially a block adjustment which I tried to explain yesterday.
/Steve
----- Original Message ----- From: "Chris Gough" <
address@hidden>
To: <
address@hidden>
Sent: Friday, October 09, 2009 12:26 AM
Subject: Re: [Paparazzi-devel] Photogrammetry (was georeferencing video stream)
That's an awsome response, thank you.
Sounds like the "direct
georeferenced video stream" approach is
fesable, but likely to give me dissapointing results (be of dubious
value). I think I'll try to learn patience and more about block
adjustment and the other things you have linked to.
Chris
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