Help Required - XY Error in Mobile Laser Scanning

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ganeshg
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Help Required - XY Error in Mobile Laser Scanning

Post by ganeshg » Tue Mar 25, 2014 5:22 am

Hi All
We are getting xy error in the Mobile Laser scanning point cloud (the length measured by both the scanner are slightly differing).

If anyone knows,the causes of the problem and the way to solve, please help me.

Ganeshan Gopalan
ganeshan.gopalan@geokno.com
Ganeshan Gopalan
Business Analyst
Geokno India PVT LTD
Bangalore,India

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Re: Help Required - XY Error in Mobile Laser Scanning

Post by Andrei.Iasashnykh » Mon Apr 14, 2014 5:26 am

If I understand correctly, the error between the data from two scanners in one run?
I do not know what equipment you are used, but the problem can be as follows:
one and the same object is removed by different scanners at different times. Consequently, different quality reception GNSS. (see pic.)

Image

I also do not know what software you are using, but in the Alignment tool must be presents sets like"Minimum time gap between pointclouds" and "Maximum time difference for linking clouds" (in Expert mode in Riegl RiProcess). After change this parameters soft will think that pointclouds from two scanners are from different runs.
Per aspera ad astra... And sorry for my English

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Re: Help Required - XY Error in Mobile Laser Scanning

Post by ksyen » Thu Feb 26, 2015 2:53 am

Without see sample of your scan data or screen shoot and your SBET solution from POSPac (which I assume you use), I can only speculate:
Possible reasons:
1) Bad lasers sensor alignment. This will should up in all your scans with good GNSS signal and short baseline.

If the XY offset only appear on a particular project but not the others project before or after,
2) you may have a bad "yaw" angle estimate from you GNSS/IMU POSPac solution that may be cause by:
a) Long GNSS outage
b) GAMS cut in and out. Try process it with GAMS disable.
c) Did not drive the system and allow for complete GNSS initialization before initial 5 min static session

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