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Author Topic: Strange artifact after DEM creation  (Read 1733 times)

jurijs.jeshkins

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Strange artifact after DEM creation
« on: March 05, 2019, 04:42:47 PM »
I have very strange artifact after DEM creation. You can see in attached file, that a strange crack appeared. As it is seen in the profile line, there is a ~2m gap between 2 parts of the DEM.

I combined pictures, that were acquired during 3 days of the expedition to the glacier. During all days GCPs were used. Lighting conditions vary between days, as well as flight altitude (because glacier is somewhat steep and UAV calculates altitude from the home point and stays on that altitude).

I have 2 questions:
1) What can I do with the pictures or project to eliminate this artifact?
2) What should I do better next time, when I will be doing UAV projects like this?

Dave Martin

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Re: Strange artifact after DEM creation
« Reply #1 on: March 05, 2019, 06:08:28 PM »
Jurijs, If this is acquired with DJI UAV, then this will be the infamous DJI height-above-takeoff bug - just search here on the forum for   DJI height   and you'll find lots about it and also haw you can resolve it.

Dave

Alexey Pasumansky

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Re: Strange artifact after DEM creation
« Reply #2 on: March 05, 2019, 06:22:52 PM »
Hello jurijs.jeshkins,

If it is the height problem mentioned above by Dave, you can also try to perform the following actions:
- after adding all the images from both flights to the same chunk uncheck all cameras in the Reference pane,
- align photos using Generic preselection option only,
- georeference the model using GCPs only (without camera locations, thus keeping them unchecked in the Reference pane all the time).

Another option is to correct the height for one of the flights after loading photos (in order to fit the second flight) and then process the data as usual.
Best regards,
Alexey Pasumansky,
Agisoft LLC

jurijs.jeshkins

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Re: Strange artifact after DEM creation
« Reply #3 on: March 06, 2019, 01:11:07 PM »
Ok, I will try to do General preselection with all the cameras turned off. If this won't work, I will look for another method.