Classify points inside overlapping flightlines

263 views
Skip to first unread message

Giuseppe Gentili

unread,
Mar 17, 2019, 3:48:19 PM3/17/19
to LAStools - efficient tools for LiDAR processing
Hi,

How is possible to classify the points that are in the overlap area of flightlines ?

The purpose is to run lasthin or lasvoxel only onto the points that fall only the overlap areas.

I have experienced lasoverage but the “overage” criteria is different from the “overlap” criteria.

Points can have the source ID information to help to find the boundary of each flightline.
Regards,

Giuseppe

Jean-François Bourdon

unread,
Mar 18, 2019, 12:31:03 PM3/18/19
to LAStools - efficient tools for LiDAR processing
The way I have done something similar in the past was to
  1. make a series of concave hull with lasboundary on each flightlines
  2. make union operation on all hulls generated with a GIS (or GDAL)
  3. isolate overlap areas and export those as SHP
  4. use lasclip with option -classify (or -flag_as_withheld if you need to keep original classification) and -interior to isolate the points falling inside the polygon/overlap area
Not exactly a single line operation, but it works.

Giuseppe Gentili

unread,
Mar 18, 2019, 3:24:51 PM3/18/19
to LAStools - efficient tools for LiDAR processing

Hi Jean-François,

many thanks for your reply.
I agree that this is not a single line operation and unfortunately is should be processed also outside lastoos environment.
lasoverlap command could be designated to perform this process but unfortuantely it produces a "grid". 
I hope that lasoverlap can be integrated with this functionality.
Giuseppe

Martin Isenburg

unread,
Mar 21, 2019, 5:21:08 PM3/21/19
to LAStools - efficient command line tools for LIDAR processing
Hello,

i've added a new function '-entire_overlap' to the lasoverage module that can compute and then classify/flag/remove the *entire* overlap for tiles as well as for flightlines:


It's available in todays release of LAStools which also contains an important update to the LASzip decompressor for those folks who are using LAZ files that contain the new point types and extended classification codes higher than 31. You can download the new release here:


lasoverage.exe -version
LAStools (by mar...@rapidlasso.com) version 190321 (commercial)

lasoverage -v -i 1_tiles_raw\*.laz ^
                  -entire_overlap ^
                  -odir 2_tiles_over -olaz
processing file '1_tiles_raw\668500_1586000.laz' with 187199 points using step 1.
WARNING: input has only one flightline ID 2. there is no overlap to compute.
took 0.561 sec. computing flightline overlap.
took 0 sec. outputting ...
took 0.512 sec. found 0 overlap points.
done with '2_tiles_over\668500_1586000.laz'. total time 1.073 sec.
processing file '1_tiles_raw\669000_1586000.laz' with 847255 points using step 1.
took 1.733 sec. computing flightline overlap.
took 0 sec. outputting ...
took 1.904 sec. found 699080 overlap points.
done with '2_tiles_over\669000_1586000.laz'. total time 3.637 sec.
processing file '1_tiles_raw\669500_1586000.laz' with 545549 points using step 1.
took 1.221 sec. computing flightline overlap.
took 0 sec. outputting ...
took 1.085 sec. found 417659 overlap points.
done with '2_tiles_over\669500_1586000.laz'. total time 2.306 sec.
processing file '1_tiles_raw\670000_1586000.laz' with 76959 points using step 1.
WARNING: input has only one flightline ID 4. there is no overlap to compute.
took 0.141 sec. computing flightline overlap.
took 0 sec. outputting ...
took 0.156 sec. found 0 overlap points.
done with '2_tiles_over\670000_1586000.laz'. total time 0.297 sec.

lasoverage.exe -v -i 0_strips_raw\*sub.laz ^
                          -flights_are_flightlines ^
                          -entire_overlap ^
                          -odir 0_strips_over -olaz 
processing file '0_strips_raw\Ayutthaya_line_2sub.laz' with 651856 points using step 1.
processing file '0_strips_raw\Ayutthaya_line_3sub.laz' with 615727 points using step 1.
processing file '0_strips_raw\Ayutthaya_line_4sub.laz' with 389379 points using step 1.
took 4.355 sec. computing flightline overlap.
took 0.023 sec. outputting ...
took 2.685 sec. found 1116817 overlap points.
done with 3 files. total time 7.063 sec.

Regards,

Martin @rapidlasso

--
Download LAStools at
http://lastools.org
http://rapidlasso.com
Be social with LAStools at
http://facebook.com/LAStools
http://twitter.com/LAStools
http://linkedin.com/groups/LAStools-4408378
Manage your settings at
http://groups.google.com/group/lastools/subscribe
Reply all
Reply to author
Forward
0 new messages