lascontrol

[Andrew Watson]

Hi All,

Can anyone tell me what the "abs" of abs/rms/stddev refers to and how it is calculated. RMS and STDDEV is ok.

Thanks

Andrew

[Martin Isenburg]

Hello Andrew,

abs should be more appropriately named avgabs. It is the average of the absolute value of the error across at all LiDAR covered control points.  I realize that I should also include the avg error that expresses an average of the actual error values and not only that of their absolute values ... next release. (-:

Regards,

Martin @rapidlasso

http://rapidlasso.com - fast tools to QC/QA your LiDARs

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[Martin Isenburg]

Hello,

in the latest release of LAStools (130402) the lascontrol
functionality has been changed to also include reporting the absolute
error like in this example here (which should have been part of the
quality checking pipeline that I described in this earlier thread
here:

http://groups.google.com/group/lastools/browse_thread/thread/d4dd34cf097b54a8

below the way to do this check. If you want to run it yourself simply
download the files linked in the thread above, put them into a folder
called "strips_raw" and copy the control points at the very (!) end of
this message into a text file called "cps.csv" ...

C:\lastools\bin>lascontrol -i strips_raw\*.laz -cp strips_raw\cps.csv -
parse sxyz
diff,lidar_z,Type,Easting,Northing,Z
0.1451,74.3151,Open/Paved,273299.68,4715133.88,74.17
0.0190857,73.8691,Open/Paved,273477.61,4714979.29,73.85
0.08872,72.5887,Open/Paved,274001.2,4714540.29,72.5
-0.00419681,73.3358,Open/Paved,273670.13,4714817.4,73.34
0.054868,74.3149,Open/Paved,273677.42,4715018.66,74.26
0.0318439,73.1818,Open/Paved,273400.1,4714528.98,73.15
-0.0720668,95.6279,Open/Paved,274511.59,4714905.97,95.7
-0.0670072,120.113,Open/Paved,275074.66,4714841.98,120.18
0.0756029,113.486,Open/Paved,275409.65,4714994.76,113.41
0.00132683,73.4613,Field,273321.18,4714946.83,73.46
0.0750162,74.425,Field,273601.49,4715101.78,74.35
0.00228472,73.9723,Field,273646.76,4714972.94,73.97
0.166194,71.2962,Field,273890.5,4714457.59,71.13
-0.392266,104.738,Field,274650.24,4714903.44,105.13
-0.0705893,98.5194,Field,274522.36,4714829.74,98.59
-0.423622,127.206,Field,275474.47,4714780.03,127.63
0.217528,120.938,Field,275636.39,4714868.85,120.72
-0.12489,115.985,Field,274747.37,4714932.57,116.11
0.0195411,126.92,Field,272795.36,4714503.86,126.9
17.0342,144.744,Forested,272547.02,4714623.09,127.71
9.20693,88.5669,Forested,273205.33,4714900.27,79.36
26.355,139.835,Forested,272530.52,4715045.46,113.48
20.2143,140.524,Forested,275237.48,4715049.57,120.31
14.5363,119.526,Forested,275268.37,4714543.82,104.99
0.173861,109.034,Forested,274666.09,4714497.49,108.86
20.5742,113.744,Forested,274403.56,4715053.43,93.17
0.00432622,114.644,Forested,274901.6,4714493.63,114.64
23.8816,128.372,Forested,274658.37,4715072.74,104.49
0.3645,72.4245,Forested,274121.73,4714524.51,72.06
sampled TIN at 29 of 29 control points.
avgabs/rms/stddev/avg of elevation errors are
4.63438/9.61987/8.62324/4.55475 meter. skew is 1.47593.

=========================================================

put the lines right below this one into a text file called "cps.csv":
Type,Easting,Northing,Z
Open/Paved,273299.68,4715133.88,74.17
Open/Paved,273477.61,4714979.29,73.85
Open/Paved,274001.2,4714540.29,72.5
Open/Paved,273670.13,4714817.4,73.34
Open/Paved,273677.42,4715018.66,74.26
Open/Paved,273400.1,4714528.98,73.15
Open/Paved,274511.59,4714905.97,95.7
Open/Paved,275074.66,4714841.98,120.18
Open/Paved,275409.65,4714994.76,113.41
Field,273321.18,4714946.83,73.46
Field,273601.49,4715101.78,74.35
Field,273646.76,4714972.94,73.97
Field,273890.5,4714457.59,71.13
Field,274650.24,4714903.44,105.13
Field,274522.36,4714829.74,98.59
Field,275474.47,4714780.03,127.63
Field,275636.39,4714868.85,120.72
Field,274747.37,4714932.57,116.11
Field,272795.36,4714503.86,126.9
Forested,272547.02,4714623.09,127.71
Forested,273205.33,4714900.27,79.36
Forested,272530.52,4715045.46,113.48
Forested,275237.48,4715049.57,120.31
Forested,275268.37,4714543.82,104.99
Forested,274666.09,4714497.49,108.86
Forested,274403.56,4715053.43,93.17
Forested,274901.6,4714493.63,114.64
Forested,274658.37,4715072.74,104.49
Forested,274121.73,4714524.51,72.06