new tutorial: Removing Low Noise from RIEGL’s VUX-1 UAV LiDAR

[Martin Isenburg]

Hello,

We recently visited the team of Dr. Ariel Blanco at UP Diliman in the Philippines to conduct a workshop on processing high resolution LiDAR from low-flying drones or helicopters. Test data collected with RIEGL's VUX-1 UAV near El Nido, Palawan was graciously provided by AB Surveying. As we are allowed to share this data for educational purposes, we wrote up a new step-by-step tutorial on how to observe and overcome unusual noise patterns and generate a high-resolution Digital Terrain Model DTM from the point cloud ... (-:

https://rapidlasso.com/2018/04/09/removing-low-noise-from-riegls-vux-1-uav-lidar-flown-in-the-philippines/

Regards,

Martin @rapidlasso

[Martin Isenburg]

Hello,

What is the reason for this noise? At first I hypothesized - without further explanation - that this may have to do with the waveform processing.That may not be an entirely accurate description.  In s discussion with another LAStools user who has flown the RIEGL VUX-1 UAV sensor we concluded that the noise we are removing here was to a large degree caused by either flying outside the set MTA-zone (in terms of range) or by processing the data in the wrong MTA-zone (which is nearly the same). One could potentially confirm this by having the flight trajectory. It would also be good to know what pulse rate the survey was flown with.

Being outside of the assumed MTA-zone happens easily with the VUX. This is according to the user that I have discussed this with who has done that himself on occasion. However, one can eliminate the wrong returns - in case they are indeed caused by a wrong MTA-zone - quite easily if one still has access to the original SDF files and the RIEGL processing software.

That said ... the "free data" we obtained are just the "test output" from  a "test flight" for a new system that had been recently acquired, hence such issues are to be expected.

Regards.

Martin

[Alvan Karlin]

All:

Just a quick note that we have seen a similar issue with Riegl VQ1560i data.  I am not at liberty to share the data (yet), but RieglUSA has attributed the issue to gain settings and MTA processing.  Here is an example:

 

 

Al Karlin, Ph.D., CMS-L, GISP

Mapping & GIS

SWFWMD

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[Lui]

Hi!

From my experience using several Riegl scanners, the main reason for this kind of noise (missed MTA zone) is higher relative air humidity during scanning. With latest Riegl software updates some improvement can be observed. But still you should always plan how many MTA zones should be and where (in vertical sense) MTA change can happen.

Just my 0.02$

Lui

[Mark Levitski]

The Phoenix Lidar crew has put together very nice flight planning software (albeit for UAV's) that will autopilot the flight following the terrain at a constant AGL to minimize MTA zones. Granted this feature is usually used for rotary platforms, and in their case the DJI Matrice 600 or the Vapor 55 seem to be the birds used for the Riegl VUX-1. I don't have any hands on experience with that post processing to comment on any issues though.

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