las2txt with extra bytes

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Vonau, Katharina

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Aug 6, 2018, 7:25:12 AM8/6/18
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Hello everyone,

for editing our point clouds we use DTMaster. Recently we tried to import a las-file with extra bytes (stored with lasheight). We noticed that when exporting the project, we couldn't read the las-file and the containing extra bytes anymore with las2txt. But the header says that the extra bytes are still there. Is it a problem with lastools or a problem of DTMaster?

Thanks for your help
Katharina


Header of file imported:

lasinfo (180731) report for 'd:\LAS\ExtraBytes\32494_5697\dhmlas_32494_5697_1_nw_extra.las'
reporting all LAS header entries:
file signature: 'LASF'
file source ID: 0
global_encoding: 0
project ID GUID data 1-4: 00000000-0000-0000-0000-000000000000
version major.minor: 1.4
system identifier: 'LAStools (c) by rapidlasso GmbH'
generating software: 'lasheight (180731) unlicensed'
file creation day/year: 280/2017
header size: 375
offset to point data: 623
number var. length records: 1
point data format: 6
point data record length: 32
number of point records: 0
number of points by return: 0 0 0 0 0
scale factor x y z: 0.01 0.01 0.01
offset x y z: 300000 6000000 0
min x y z: 494000.00 5697000.00 299.95
max x y z: 494999.99 5697999.99 493.11
start of waveform data packet record: 0
start of first extended variable length record: 0
number of extended_variable length records: 0
extended number of point records: 9447752
extended number of points by return: 8113660 562565 388611 229703 104314 37900 10999 0 0 0 0 0 0 0 0
variable length header record 1 of 1:
reserved 0
user ID 'LASF_Spec'
record ID 4
length after header 192
description 'by LAStools of rapidlasso GmbH'
Extra Byte Descriptions
data type: 4 (short), name "height above ground", description: "vertical point to TIN distance", scale: 0.01, offset: 250
the header is followed by 2 user-defined bytes
reporting minimum and maximum for all LAS point record entries ...
X 19399998 19500001
Y -30300002 -30199999
Z 29993 49310
intensity 0 0
return_number 1 7
number_of_returns 1 7
edge_of_flight_line 0 0
scan_direction_flag 0 0
classification 1 26
scan_angle_rank -33 33
user_data 0 255
point_source_ID 0 0
gps_time 0.000000 0.000000
extended_return_number 1 7
extended_number_of_returns 1 7
extended_classification 1 26
extended_scan_angle -5500 5500
extended_scanner_channel 0 0
WARNING: 435 points outside of header bounding box
number of first returns: 8113660
number of intermediate returns: 520821
number of last returns: 8264904
number of single returns: 7451633
overview over extended number of returns of given pulse: 7451633 564340 548230 455996 264629 114229 48695 0 0 0 0 0 0 0 0
histogram of classification of points:
662027 unclassified (1)
8080260 ground (2)
226 bridge deck (17)
520821 Reserved for ASPRS Definition (19)
184397 Reserved for ASPRS Definition (20)
21 Reserved for ASPRS Definition (26)
+-> flagged as synthetic: 21
WARNING: real max x larger than header max x by 0.020000
WARNING: real min x smaller than header min x by 0.020000
WARNING: real max y larger than header max y by 0.020000
WARNING: real min y smaller than header min y by 0.020000
WARNING: real min z smaller than header min z by 0.020000




Header of file exported:

lasinfo (180731) report for 'd:\LAS\ExtraBytes\32494_5697\dhmlas_32494_5697_1_nw_extra_dtmaster.las'
reporting all LAS header entries:
file signature: 'LASF'
file source ID: 0
global_encoding: 0
project ID GUID data 1-4: 00000000-0000-0000-0000-000000000000
version major.minor: 1.4
system identifier: 'LAStools (c) by rapidlasso GmbH'
generating software: 'Trimble/inpho/pak'
file creation day/year: 217/2018
header size: 375
offset to point data: 621
number var. length records: 1
point data format: 6
point data record length: 30
number of point records: 9447752
number of points by return: 8113660 562565 388611 229703 104314
scale factor x y z: 0.001 0.001 0.001
offset x y z: 494000 5697050 300
min x y z: 493999.980 5696999.980 299.930
max x y z: 495000.010 5698000.010 493.100
start of waveform data packet record: 0
start of first extended variable length record: 0
number of extended_variable length records: 0
extended number of point records: 9447752
extended number of points by return: 8113660 562565 388611 229703 104314 37900 10999 0 0 0 0 0 0 0 0
variable length header record 1 of 1:
reserved 0
user ID 'LASF_Spec'
record ID 4
length after header 192
description 'by LAStools of rapidlasso GmbH'
Extra Byte Descriptions
data type: 4 (short), name "height above ground", description: "vertical point to TIN distance", scale: 0.01, offset: 250
reporting minimum and maximum for all LAS point record entries ...
X -20 1000010
Y -50020 950010
Z -70 193100
intensity 0 0
return_number 1 7
number_of_returns 1 7
edge_of_flight_line 0 0
scan_direction_flag 0 0
classification 1 26
scan_angle_rank -33 33
user_data 0 255
point_source_ID 0 0
gps_time 0.000000 0.000000
extended_return_number 1 7
extended_number_of_returns 1 7
extended_classification 1 26
extended_scan_angle -5500 5500
extended_scanner_channel 0 0
WARNING: there is coordinate resolution fluff (x10) in XYZ
number of first returns: 8113660
number of intermediate returns: 520821
number of last returns: 8264904
number of single returns: 7451633
WARNING: point type is 6 but (legacy) number of point records in header is 9447752 instead zero.
WARNING: point type is 6 but (legacy) number of points by return [1] in header is 8113660 instead zero.
WARNING: point type is 6 but (legacy) number of points by return [2] in header is 562565 instead zero.
WARNING: point type is 6 but (legacy) number of points by return [3] in header is 388611 instead zero.
WARNING: point type is 6 but (legacy) number of points by return [4] in header is 229703 instead zero.
WARNING: point type is 6 but (legacy) number of points by return [5] in header is 104314 instead zero.
overview over extended number of returns of given pulse: 7451633 564340 548230 455996 264629 114229 48695 0 0 0 0 0 0 0 0
histogram of classification of points:
662027 unclassified (1)
8080260 ground (2)
226 bridge deck (17)
520821 Reserved for ASPRS Definition (19)
184397 Reserved for ASPRS Definition (20)
21 Reserved for ASPRS Definition (26)
+-> flagged as synthetic: 21

Martin Isenburg

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Aug 6, 2018, 7:38:11 AM8/6/18
to LAStools - efficient command line tools for LIDAR processing
Hello,

Your other software is to blame here because it does not actually export the two additional "extra bytes" per point that store the "additional attribute" that represents the "height above ground". This is obvious when you look at the point data record length before and after. 

before:
  point data format:          6
  point data record length:   32

after:
  point data format:          6
  point data record length:   30

However, it still did export the VLR that references these two extra bytes and this means the file is no longer specification confirm. Furthermore the other software miraculously increased the resolution of the points from cm to mm so that each coordinate now has three instead of two decimal digits. Obviously the last digit is always zero as evident here:

  min x y z:                  493999.980 5696999.980 299.930
  max x y z:                  495000.010 5698000.010 493.100
[...]

  X                 -20    1000010
  Y              -50020     950010
  Z                 -70     193100

and lasinfo find those silly zeros and warns about them as "fluff"
 
WARNING: there is coordinate resolution fluff (x10) in XYZ

because the resulting files do not compress as well.

Regards,

Martin

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