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Author Topic: Towards precision (over and over again)  (Read 5846 times)

George

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Towards precision (over and over again)
« on: December 14, 2012, 03:30:58 PM »
Here are some results of practical comparision of LIDAR scanning (DTM - National service) vs. Photoscan job.
XYZ in meters
The accuracy is just of 5-10 cm (or exactly 5-6 cm with st.dev 5 cm:  4 samples on average 700 meters each). DEM clearly demonstrates vthe egetation at the site vs. cleaned DTM.
« Last Edit: December 17, 2012, 02:09:43 AM by George »

Mohabon

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Re: Towards precision (over and over again)
« Reply #1 on: December 14, 2012, 07:43:20 PM »
Hello,


What was your ground pixel resolution?

I have been running some tests with PS PRO processing using 12Mpix images acquired by UAV flying at 150m and i easily match LIDAR with accuracy = +- 5cm.

Vegetation is well known big annoying issue which could be overruin by using some LASTOOLS etc.

Let's hope Agisoft will implement the base-height field model as suggested in some previous topic!  ;D



George

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Re: Towards precision (over and over again)
« Reply #2 on: December 15, 2012, 11:22:00 PM »
Hi
1 pix approx. 3 cm at this mission
What do you mean under "... Vegetation ... Could be overruin by ... LASTool"?
Did you do any conversions of DEM to DTM with that tool?
I really wonder if that is possible.
Cheers

fpbv

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Re: Towards precision (over and over again)
« Reply #3 on: December 16, 2012, 03:54:08 PM »
I wonder if LASTools can do DTM...

George

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Re: Towards precision (over and over again)
« Reply #4 on: December 16, 2012, 08:41:18 PM »
I also wonder ... It seems like Mohabon might have used it (at least it looks like that from his/her post). If so than this is an advantage ... Tho the DTM may still deviate from official i.e. real DTM
« Last Edit: December 16, 2012, 10:38:58 PM by George »

George

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Re: Towards precision (over and over again)
« Reply #5 on: December 17, 2012, 02:13:41 AM »
... actually, the answer is YES ... LASTOOL can do it ...
check for ex. lasheight and lasground at http://www.cs.unc.edu/~isenburg/lastools/
but this is based on LIDAR scanning data ...
Though the question is how one can do it based on the aerial photography point cloud which is not a LIDAR?

Finally, read this answer from LASTOOLs developer
https://groups.google.com/forum/?fromgroups#!searchin/lastools/photography/lastools/9xsy9gSAw10/wPvfH7YR2N8J

"... lasground was not
designed to work with photogrammetric data but seems to work fairly
well in practice. but if you have no "ground returns" in a dense
forest i don;t see how you can remove the vegetation ..."
« Last Edit: December 17, 2012, 02:29:15 AM by George »