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Author Topic: Banana shape effect  (Read 4370 times)

dmct

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Banana shape effect
« on: September 15, 2016, 11:01:08 PM »
Hello Agisoft community!

I have a quick and somewhat simple question.

I´ve been working with photogrammetry to quantify erosion on a certain beach. To do so I take aerial photography with a UAV  and then generate dense point clouds with Agisoft Photoscan Pro. Due to the fact that I need really precise measurements I have been using GCP´s which I georeference using an RTK GPS to geotag our models. All tough the GCP´s are permanent marks that we placed along the coastline, and have been used in the monthly models to standardise them, some models have resulted with a low banana shape effect.

What might be causing this? I have been flying monthly since march using the same flight plan and geotag my models with the same GCP´s.

I´ve attached two images, one corresponding to march and the other to august so you can se the difference between them even after been georeferenced using the GCP´s.



Thanks in advanced

Alexey Pasumansky

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Re: Banana shape effect
« Reply #1 on: September 16, 2016, 11:23:20 AM »
Hello dmct,

Have you used optimization feature and which accuracy settings you are using for cameras and markers?
Best regards,
Alexey Pasumansky,
Agisoft LLC

dmct

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Re: Banana shape effect
« Reply #2 on: September 20, 2016, 11:19:52 PM »
Yes I have. For camera I used 10m and 2 degree accuracy, and for markers I used 0.01m for marker accuracy. I have not calculated my GCPs accuracy but since I am using a RTK GPS that works with cm accuracy I decided to use that value.

Alexey Pasumansky

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Re: Banana shape effect
« Reply #3 on: September 20, 2016, 11:52:10 PM »
Hello dmct,

Maybe you can send the project with the alignment results and placed markers to support@agisoft.com (no need of dense cloud, mesh and etc.)?
Best regards,
Alexey Pasumansky,
Agisoft LLC

dmct

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Re: Banana shape effect
« Reply #4 on: September 21, 2016, 07:34:35 PM »
Sure, will do. Thank you!

jwoods

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Re: Banana shape effect
« Reply #5 on: September 21, 2016, 10:57:49 PM »
Are you adding the GCP's after alignment or before alignment?  Do you get the bowl effect without the GCP's?

tutoss

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Re: Banana shape effect
« Reply #6 on: September 26, 2016, 06:08:14 PM »
you can try add a previous camera calibration parameter and fix it. Works for me.

tutoss