0 values for return_number and number_of_returns

[Katie Strattman]

Hello LiDAR community,

I am currently collecting mobile with a hand-help and backpack-mounted TLS data using a Velodyne VPL-16 system in densely vegetated grassland and shrubland plots and creating .laz files with proprietary software. I have noticed that all of my output .laz files have 0 values for most of the metadata fields. I also get this error when running any tools in LAStools or lidR:

WARNING: no payload for LASF_Projection VLR with record_id 2112.

I am quite new to TLS data and wanted to see if anyone else has faced similar issues? If so, is there a way to set the metadata values such as return_number and number_of_returns based on the gpstime? Or is this a problem with my scanning methodology in the densely vegetated areas?

Here is the output for lasinfo for one of my plots:

kstratt@fatc1:~/terraces/datasets/hovermap/fieldwork/oct24 > lasinfo -i Oct24_04_Output_laz1_4.laz
WARNING: no payload for LASF_Projection VLR with record_id 2112.
lasinfo (210720) report for 'Oct24_04_Output_laz1_4.laz'
reporting all LAS header entries:
  file signature:             'LASF'
  file source ID:             0
  global_encoding:            17
  project ID GUID data 1-4:   00000000-0000-0000-0000-000000000000
  version major.minor:        1.4
  system identifier:          'Hovermap'
  generating software:        'LASzip DLL 3.4 r3 (191111)'
  file creation day/year:     296/2022
  header size:                375
  offset to point data:       867
  number var. length records: 2
  point data format:          1
  point data record length:   33
  number of point records:    32213663
  number of points by return: 0 0 0 0 0
  scale factor x y z:         0.001 0.001 0.001
  offset x y z:               5.681123969292924 -5.017259573634759 -0.2080482457
84458
  min x y z:                  -209.874 -216.211 -209.767
  max x y z:                  209.834 204.250 201.544
WARNING: stored resolution of min_x not compatible with x_offset and x_scale_factor: -209.8738157690625
WARNING: stored resolution of min_y not compatible with y_offset and y_scale_factor: -216.2111462048762
WARNING: stored resolution of min_z not compatible with z_offset and z_scale_factor: -209.76710915145463
WARNING: stored resolution of max_x not compatible with x_offset and x_scale_factor: 209.83412713096183
WARNING: stored resolution of max_y not compatible with y_offset and y_scale_factor: 204.25019726306425
WARNING: stored resolution of max_z not compatible with z_offset and z_scale_factor: 201.54400036174502
  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: 32213663
  extended number of points by return: 27735444 4478219 0 0 0 0 0 0 0 0 0 0 0 0
0
variable length header record 1 of 2:
  reserved             0
  user ID              'LASF_Spec'
  record ID            4
  length after header  384
  description          'LASzip DLL 3.4 r3 (191111)'
    Extra Byte Descriptions
      data type: 2 (char), name "Ring", description: "Lidar Ring in Velodyne", scale: 1, offset: 0
      data type: 9 (float), name "Range", description: "Range from Lidar to Point", scale: 1, offset: 0
variable length header record 2 of 2:
  reserved             0
  user ID              'LASF_Projection'
  record ID            2112
  length after header  0
  description          'OGC WKT'
LASzip compression (version 3.4r3 c2 50000): POINT10 2 GPSTIME11 2 BYTE 2
reporting minimum and maximum for all LAS point record entries ...
  X             -109450      87418
  Y             -109279      79928
  Z              -44527      68763
  intensity           0        225
  return_number       0          1
  number_of_returns   0          0
  edge_of_flight_line 0          0
  scan_direction_flag 0          0
  classification      0          0
  scan_angle_rank     0          0
  user_data           0          0
  point_source_ID     0          0
  gps_time 1666577645.684336 1666578255.834871
  attribute0          0         15  ('Ring')
  attribute1    1.50011    99.9995  ('Range')
number of first returns:        32213663
number of intermediate returns: 0
number of last returns:         32213663
number of single returns:       32213663
WARNING: for return 1 real number of points by return is 4478219 but header entry was not set.
WARNING: real extended number of points by return [1] is 4478219 - different from header entry 27735444.
WARNING: real extended number of points by return [2] is 0 - different from header entry 4478219.
WARNING: there are 27735444 points with return number 0
WARNING: there are 32213663 points with a number of returns of given pulse of 0
histogram of classification of points:
        32213663  never classified (0)

I am happy to send the .laz file if necessary. Thank you in advance!

Thanks,

Katie