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Author Topic: model lower than ground control  (Read 2192 times)

JMR

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model lower than ground control
« on: June 24, 2014, 12:48:09 AM »
Hello:
I've done a project (aerial work) in wich an average deviation of -0.07m in dense cloud with respecto to ground control points (targets) is annoying me.
It seems that Photoscan underestimates elevations of all automatic matchings causing an error lowering results by some amount. Note that none of the ground control points exhibits a deviation with the opposite sign, and that makes it unlikely that the error came from a bad adjustment of the bundle block.
In this project all photos suffer from noticeable defocusing due to a bad focus set but they still  appeared to be useable.
Does someone have experienced something like this?

JMR

Ron

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Re: model lower than ground control
« Reply #1 on: June 26, 2014, 02:19:43 PM »
Hi,
I'm not sure about your case but when I have similar problems I find I need to make adjustments to  my weightings. I spend quite a bit of time here making sure my ground control is satisfactory before forming the dense cloud.

Go to the Ground Control Settings dialog box in the Ground Control Pane to adjust your weighting.

 I uncheck camera positions and rely on ground control. All ground control points should be checked.

Then optimise. Note that when you optimise you will loose your dense cloud.

My typical settings are 10m, 0.005m, 0.005m 1pix, 2pix. Note that on the last option Agisoft recommends leaving this at 4pix.
This should give you a + and - range for your errors.
If errors remain large also check for errors in each ground control points.