Finland data set - lasinfo

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Jost Hobic

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Jun 25, 2016, 3:18:37 PM6/25/16
to LAStools - efficient tools for LiDAR processing
Hi!

I have peaked into Finland LiDAR data set. I checked it with lasinfo and it gave me this warning over classification points


classification histogram with bin size 1
  bin 1 has 1520583
  bin 2 has 4099092
  bin 3 has 1602448
  bin 7 has 30
  bin 9 has 2660
  average classification 2.01393 for 7224813 element(s)
number of first returns:        5621513
number of intermediate returns: 202906
number of last returns:         5622365
number of single returns:       4221971
covered area in square units/kilounits: 8642036/8.64
point density: all returns 0.84 last only 0.65 (per square units)
      spacing: all returns 1.09 last only 1.24 (in units)
WARNING: for return 1 real number of points by return is 5621513 but header entry was not set.
WARNING: for return 2 real number of points by return is 1400293 but header entry was not set.
WARNING: for return 3 real number of points by return is 130472 but header entry was not set.
WARNING: for return 4 real number of points by return is 72535 but header entry was not set.
overview over number of returns of given pulse: 4221971 2539086 173792 289964 0 0 0
histogram of classification of points:
         1520583  unclassified (1)
         4099092  ground (2)
         1602448  low vegetation (3)
              30  noise (7)
            2660  water (9)

Does this mean that LiDAR data isnt optimised or what?

Thanks!

Martin Isenburg

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Jun 26, 2016, 4:30:56 AM6/26/16
to LAStools - efficient command line tools for LIDAR processing
Hello Jost,

the LAS format specification states that in the LAS 1.0 to LAS 1.3 headers there are 5 counters that should be correctly populated to indicate how many 1st, 2nd, 3rd, 4th, and 5th return there are in the file. It seems in your LAS / LAZ file those are all set to zero. You can repair these counters "in-place" by giving lasinfo the additional command '-repair_counters'.


Here an example using the 'fusa.laz' data set. First we copy the data set so we don't mess with the original file:

D:\LAStools\bin>copy ..\data\fusa.laz fusa.laz

Now we set the counters to zero like in your file:

D:\LAStools\bin>lasinfo -i fusa.laz -set_number_of_points_by_return 0 0 0 0 0
lasinfo (160606) report for fusa.laz
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:        1.1
  system identifier:          'LAStools (c) by Martin Isenburg'
  generating software:        'lasclassify (110920) unlicensed'
  file creation day/year:     40/2010
  header size:                227
  offset to point data:       321
  number var. length records: 1
  point data format:          1
  point data record length:   28
  number of point records:    277573
  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:               0 0 0
  min x y z:                  277750.00 6122250.00 42.21
  max x y z:                  277999.99 6122499.99 64.35
variable length header record 1 of 1:
  reserved             43707
  user ID              'LASF_Projection'
  record ID            34735
  length after header  40
  description          'by LAStools of Martin Isenburg'
    GeoKeyDirectoryTag version 1.1.0 number of keys 4
      key 1024 tiff_tag_location 0 count 1 value_offset 1 - GTModelTypeGeoKey: ModelTypeProjected
      key 3072 tiff_tag_location 0 count 1 value_offset 32754 - ProjectedCSTypeGeoKey: WGS 84 / UTM 54S
      key 3076 tiff_tag_location 0 count 1 value_offset 9001 - ProjLinearUnitsGeoKey: Linear_Meter
      key 4099 tiff_tag_location 0 count 1 value_offset 9001 - VerticalUnitsGeoKey: Linear_Meter
LASzip compression (version 2.0r1 c2 50000): POINT10 2 GPSTIME11 2
reporting minimum and maximum for all LAS point record entries ...
  X            27775000   27799999
  Y           612225000  612249999
  Z                4221       6435
  intensity          10      62293
  return_number       1          3
  number_of_returns   1          3
  edge_of_flight_line 0          0
  scan_direction_flag 0          0
  classification      1          6
  scan_angle_rank    79        103
  user_data           0        197
  point_source_ID     1          1
  gps_time 5880.963028 5886.739738
number of first returns:        263413
number of intermediate returns: 283
number of last returns:         263370
number of single returns:       249493
WARNING: for return 1 real number of points by return is 263413 but header entry was not set.
WARNING: for return 2 real number of points by return is 13879 but header entry was not set.
WARNING: for return 3 real number of points by return is 281 but header entry was not set.
overview over number of returns of given pulse: 249493 27232 848 0 0 0 0
histogram of classification of points:
           17553  unclassified (1)
          180868  ground (2)
           37030  high vegetation (5)
           42122  building (6)

And yes ... this has really changed permanently in the file:

D:\LAStools\bin>lasinfo -i fusa.laz
lasinfo (160606) report for fusa.laz
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:        1.1
  system identifier:          'LAStools (c) by Martin Isenburg'
  generating software:        'lasclassify (110920) unlicensed'
  file creation day/year:     40/2010
  header size:                227
  offset to point data:       321
  number var. length records: 1
  point data format:          1
  point data record length:   28
  number of point records:    277573
  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:               0 0 0
  min x y z:                  277750.00 6122250.00 42.21
  max x y z:                  277999.99 6122499.99 64.35
variable length header record 1 of 1:
  reserved             43707
  user ID              'LASF_Projection'
  record ID            34735
  length after header  40
  description          'by LAStools of Martin Isenburg'
    GeoKeyDirectoryTag version 1.1.0 number of keys 4
      key 1024 tiff_tag_location 0 count 1 value_offset 1 - GTModelTypeGeoKey: ModelTypeProjected
      key 3072 tiff_tag_location 0 count 1 value_offset 32754 - ProjectedCSTypeGeoKey: WGS 84 / UTM 54S
      key 3076 tiff_tag_location 0 count 1 value_offset 9001 - ProjLinearUnitsGeoKey: Linear_Meter
      key 4099 tiff_tag_location 0 count 1 value_offset 9001 - VerticalUnitsGeoKey: Linear_Meter
LASzip compression (version 2.0r1 c2 50000): POINT10 2 GPSTIME11 2
reporting minimum and maximum for all LAS point record entries ...
  X            27775000   27799999
  Y           612225000  612249999
  Z                4221       6435
  intensity          10      62293
  return_number       1          3
  number_of_returns   1          3
  edge_of_flight_line 0          0
  scan_direction_flag 0          0
  classification      1          6
  scan_angle_rank    79        103
  user_data           0        197
  point_source_ID     1          1
  gps_time 5880.963028 5886.739738
number of first returns:        263413
number of intermediate returns: 283
number of last returns:         263370
number of single returns:       249493
WARNING: for return 1 real number of points by return is 263413 but header entry was not set.
WARNING: for return 2 real number of points by return is 13879 but header entry was not set.
WARNING: for return 3 real number of points by return is 281 but header entry was not set.
overview over number of returns of given pulse: 249493 27232 848 0 0 0 0
histogram of classification of points:
           17553  unclassified (1)
          180868  ground (2)
           37030  high vegetation (5)
           42122  building (6)

Now we repair the counters:

D:\LAStools\bin>lasinfo -i fusa.laz -repair_counters
lasinfo (160606) report for fusa.laz
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:        1.1
  system identifier:          'LAStools (c) by Martin Isenburg'
  generating software:        'lasclassify (110920) unlicensed'
  file creation day/year:     40/2010
  header size:                227
  offset to point data:       321
  number var. length records: 1
  point data format:          1
  point data record length:   28
  number of point records:    277573
  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:               0 0 0
  min x y z:                  277750.00 6122250.00 42.21
  max x y z:                  277999.99 6122499.99 64.35
variable length header record 1 of 1:
  reserved             43707
  user ID              'LASF_Projection'
  record ID            34735
  length after header  40
  description          'by LAStools of Martin Isenburg'
    GeoKeyDirectoryTag version 1.1.0 number of keys 4
      key 1024 tiff_tag_location 0 count 1 value_offset 1 - GTModelTypeGeoKey: ModelTypeProjected
      key 3072 tiff_tag_location 0 count 1 value_offset 32754 - ProjectedCSTypeGeoKey: WGS 84 / UTM 54S
      key 3076 tiff_tag_location 0 count 1 value_offset 9001 - ProjLinearUnitsGeoKey: Linear_Meter
      key 4099 tiff_tag_location 0 count 1 value_offset 9001 - VerticalUnitsGeoKey: Linear_Meter
LASzip compression (version 2.0r1 c2 50000): POINT10 2 GPSTIME11 2
reporting minimum and maximum for all LAS point record entries ...
  X            27775000   27799999
  Y           612225000  612249999
  Z                4221       6435
  intensity          10      62293
  return_number       1          3
  number_of_returns   1          3
  edge_of_flight_line 0          0
  scan_direction_flag 0          0
  classification      1          6
  scan_angle_rank    79        103
  user_data           0        197
  point_source_ID     1          1
  gps_time 5880.963028 5886.739738
number of first returns:        263413
number of intermediate returns: 283
number of last returns:         263370
number of single returns:       249493
number of point records in header is correct.
WARNING: for return 1 real number of points by return is 263413 but header entry was not set. it was repaired.
WARNING: for return 2 real number of points by return is 13879 but header entry was not set. it was repaired.
WARNING: for return 3 real number of points by return is 281 but header entry was not set. it was repaired.
overview over number of returns of given pulse: 249493 27232 848 0 0 0 0
histogram of classification of points:
           17553  unclassified (1)
          180868  ground (2)
           37030  high vegetation (5)
           42122  building (6)

And if we run lasinfo again we see that they have been fixed in the file:

D:\LAStools\bin>lasinfo -i fusa.laz
lasinfo (160606) report for fusa.laz
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:        1.1
  system identifier:          'LAStools (c) by Martin Isenburg'
  generating software:        'lasclassify (110920) unlicensed'
  file creation day/year:     40/2010
  header size:                227
  offset to point data:       321
  number var. length records: 1
  point data format:          1
  point data record length:   28
  number of point records:    277573
  number of points by return: 263413 13879 281 0 0
  scale factor x y z:         0.01 0.01 0.01
  offset x y z:               0 0 0
  min x y z:                  277750.00 6122250.00 42.21
  max x y z:                  277999.99 6122499.99 64.35
variable length header record 1 of 1:
  reserved             43707
  user ID              'LASF_Projection'
  record ID            34735
  length after header  40
  description          'by LAStools of Martin Isenburg'
    GeoKeyDirectoryTag version 1.1.0 number of keys 4
      key 1024 tiff_tag_location 0 count 1 value_offset 1 - GTModelTypeGeoKey: ModelTypeProjected
      key 3072 tiff_tag_location 0 count 1 value_offset 32754 - ProjectedCSTypeGeoKey: WGS 84 / UTM 54S
      key 3076 tiff_tag_location 0 count 1 value_offset 9001 - ProjLinearUnitsGeoKey: Linear_Meter
      key 4099 tiff_tag_location 0 count 1 value_offset 9001 - VerticalUnitsGeoKey: Linear_Meter
LASzip compression (version 2.0r1 c2 50000): POINT10 2 GPSTIME11 2
reporting minimum and maximum for all LAS point record entries ...
  X            27775000   27799999
  Y           612225000  612249999
  Z                4221       6435
  intensity          10      62293
  return_number       1          3
  number_of_returns   1          3
  edge_of_flight_line 0          0
  scan_direction_flag 0          0
  classification      1          6
  scan_angle_rank    79        103
  user_data           0        197
  point_source_ID     1          1
  gps_time 5880.963028 5886.739738
number of first returns:        263413
number of intermediate returns: 283
number of last returns:         263370
number of single returns:       249493
overview over number of returns of given pulse: 249493 27232 848 0 0 0 0
histogram of classification of points:
           17553  unclassified (1)
          180868  ground (2)
           37030  high vegetation (5)
           42122  building (6)

Regards,

Martin @rapidlasson

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