Towards precision (over and over again)

[George]

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.

[Mohabon]

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! 

[George]

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]

I wonder if LASTools can do DTM...

[George]

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

[George]

... 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 ..."