lasdatum gsb support

[Michael Perdue]

Hello,

I'm trying to use lasdatum to do a datum transformation from NAD83CSRS to NAD83 original. This uses a GSB (grid shift binary) file that lasdatum should support in theory. However, when I feed it my gsb files it complains:

>lasdatum -grid ABCSRSV4.GSB -backward -epsg 3157 -target_epsg 26910 -i 521_5447.laz -o 521_5447_orig.laz
ERROR: num_file is not between 1 and 16 but 57. not supported.

This appears to be related to the number of layers present in the GSB files. In the case of ABCSRSV4.GSB, there are 57 SUBDATASETs, but I know some files go much higher. NTV2_0.GSB has 114 SUBDATASETs.

I'm not sure if 16 represents a technical issue or if it is more of a sanity check and an easy fix to expand the number of layers supported. Files that have fewer layers present appear to work fine. I have attached ABCSRSV4.GSB GSB for testing/reference.

Cheers,

Mike

[Jochen Rapidlasso]

Hi Mike,

we had to tackle the tool due to another matter, so we extended the maximum of sub grids to handle.

According to the specification of GSB files (NTv2 (National Transformation Version 2) Government of Ontario IT Standards (GO-ITS) Document No. 45.2 Version 1.0) the sub grids are there to refine a certain area with a finer grid.

It seems that some providers of GSB files don't refine but just organize their grids in different parts.

We also extended lasdatum to give more information about the containing grids and their dimensions. Also we give more information about the sub grid used.

To get the extended information please use the -vv argument (very verbose).

The output of your file looks like this:

Log level [VERY_VERBOSE]
LAStools lasdatum (by in...@rapidlasso.de) version 240522
padding = '1'
number of grids = '57'
grid[0], sub name = 'ABCSRSV4'
  parent = 'NONE    '
  created = '05-06-20'
  updated = '05-06-21'
  gs_count = '16605'
conversion grid 0 from 'NAD83' to 'ABCSRSV4' has 123 x 135 = 16605 shift vectors. lat[48.916667..60.083333, inc(0.083333)] long[-120.083333..-109.916667, inc(0.083333)]
grid[1], sub name = 'BANFF   '
  parent = 'ABCSRSV4'
  created = '05-06-20'
  updated = '        '
  gs_count = '231'
conversion grid 1 from 'NAD83' to 'ABCSRSV4' has 11 x 21 = 231 shift vectors. lat[51.083333..51.250000, inc(0.008333)] long[-115.583333..-115.500000, inc(0.008333)]
grid[2], sub name = 'BARHED  '
  parent = 'ABCSRSV4'
  created = '05-06-20'
  updated = '        '
  gs_count = '231'
conversion grid 2 from 'NAD83' to 'ABCSRSV4' has 21 x 11 = 231 shift vectors. lat[54.083333..54.166667, inc(0.008333)] long[-114.500000..-114.333333, inc(0.008333)]
...

grid[53], sub name = 'WANWGT  '
  parent = 'ABCSRSV4'
  created = '05-06-20'
  updated = '        '
  gs_count = '651'
conversion grid 53 from 'NAD83' to 'ABCSRSV4' has 31 x 21 = 651 shift vectors. lat[52.750000..52.916667, inc(0.008333)] long[-111.000000..-110.750000, inc(0.008333)]
grid[54], sub name = 'WESLOK  '
  parent = 'ABCSRSV4'
  created = '05-06-20'
  updated = '        '
  gs_count = '861'
conversion grid 54 from 'NAD83' to 'ABCSRSV4' has 41 x 21 = 861 shift vectors. lat[54.083333..54.250000, inc(0.008333)] long[-114.000000..-113.666667, inc(0.008333)]
grid[55], sub name = 'WETASK  '
  parent = 'ABCSRSV4'
  created = '05-06-20'
  updated = '        '
  gs_count = '651'
conversion grid 55 from 'NAD83' to 'ABCSRSV4' has 31 x 21 = 651 shift vectors. lat[52.833333..53.000000, inc(0.008333)] long[-113.500000..-113.250000, inc(0.008333)]
grid[56], sub name = 'WHITEC  '
  parent = 'ABCSRSV4'
  created = '05-06-20'
  updated = '        '
  gs_count = '451'
conversion grid 56 from 'NAD83' to 'ABCSRSV4' has 41 x 11 = 451 shift vectors. lat[54.083333..54.166667, inc(0.008333)] long[-115.833333..-115.500000, inc(0.008333)]

...

You can download a beta of lasdatum here:

 (windows and linux)
    https://downloads.rapidlasso.de/beta/lasdatum64.7z
    https://downloads.rapidlasso.de/beta/lasdatum64.tar.gz
These changes will be included in the next release as well.

Cheers,

Jochen