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Author Topic: Bad imagery alignment  (Read 2556 times)

Randy

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Bad imagery alignment
« on: March 09, 2016, 12:30:04 AM »
I'm experiencing a re-occurring problem wherein I try and create a photo mosaic and some of the images don't import, leaving gaps.  I have tried using several different parameters and the same images will still not import. 
Two things are confusing.
First, sometimes when I take import a smaller chunk, the images will import correctly, but sometimes this does not help.
Secondly, when I try and assign manual control points in two images with overlap, the problem image still fails to import. 
One consistency is that all of the images which have poor alignment, or don't import contain some water, there should be sufficient features in the images to assign points, however the point assignment never occurs

Has anyone else had this problem, and if so how did you go about fixing it?

William Ringle

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Re: Bad imagery alignment
« Reply #1 on: March 09, 2016, 01:12:31 AM »
Do mean align rather than import? If the former, probably because of the varying reflectance patterns of the water from different camera angles.

HMArnold

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Re: Bad imagery alignment
« Reply #2 on: March 09, 2016, 05:57:23 AM »
First, water is difficult for two reasons.

The first is that there are no good defining features for Photoscan to match in nearby images, so I think it tries rotating and shifting things around, then gives up and starts on the next image.

The second is that whatever features there are, like ripples, waves or reflections, change from one image to the next and confuse things even more.

If the images were taken with a UAV, there are a few things you can do to help in terms of importing or generating heading (YAW) and gimbal angle (0 for a stabilized gimbal), as well as lat/lon

If you can give Photoscan more info about how each image relates to the ones around it, you can decrease the "Accuracy" value for each camera, which causes less rotating and shifting, and in my experience, less giving up

bigben

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Re: Bad imagery alignment
« Reply #3 on: March 09, 2016, 03:42:00 PM »
Mask out the water.