Difficulty Applying GTX Tide Correction to LAS/COPC Files in LAStools (v1.5.1)

[Rlee]

Dear LAStools Support Team,

Greetings. My name is HoSeok Lee, and we are a commercial license holder of LAStools.

We are currently conducting hydrographic surveys using a multibeam echo sounder (MBES). The acquired data was originally stored in PDS format, which we later converted to LAS files programmatically.

After post-processing the data with Agisoft Metashape, we generated COPC LAZ files. Our goal has been to apply a GTX geoid file to perform tide correction, converting the Z values from DL (depth level) to ellipsoidal height.

Unfortunately, all attempts to apply this geoid correction—whether on the COPC LAZ or the original LAS files—have failed.
We are currently using LAStools version 1.5.1.

We have verified that the boundary of the GTX tide grid fully matches the spatial extent of our data. So we do not believe the issue is due to a coverage mismatch, which makes this situation all the more confusing for us.

We would greatly appreciate your assistance in identifying whether this is a known limitation, or if we may be missing a specific step or setting required for applying geoid-based tide corrections to such datasets.

Thank you in advance for your kind support, and for continuing to provide such a powerful toolset to the LiDAR and mapping community.

Sincerely,
HoSeok Lee

[LAStools - efficient tools for LiDAR processing]

Hi HoSeok Lee,

thanks for using LAStools!

lasvdatum should be able to process your data and do a elevation transformation.
Please provide some more information so we can try to help you.

What command line did you run?
What did the command output at the console window if you use the command with the verbose (-v) option?

In what way does the result appear to be incorrect?

If you can not solve it and you have answered all questions above, please send a small sample of your data together with the GTX file you are using and we will analyze the issue in detail.

Thanks,

Jochen @rapidlasso

[이호석]

Dear LAStools Support Team,

Thank you very much for your reply.

We attempted to apply a .gtx tide correction using the las2las tool in LAStools v1.5.1, both on original .las files and on .copc.laz files.

Below are the exact commands we executed:

   Using a COPC LAZ file

las2las -i "C:\Users\Lee\Desktop\QGIS\202504_LASTools\99_data\sample.copc.laz" ^
        -o "C:\Users\Lee\Desktop\QGIS\202504_LASTools\99_data\sample_ellipsoid.laz" ^

        -geoid "C:\Users\Lee\Desktop\QGIS\202504_LASTools\tide\WMSL_IMSL_2018_fina_32.gtx" -v  

  Console output

  (run: Failed to execute las2las ... exit code: 2)

  Using an original LAS file

las2las -i "C:\Users\Lee\Desktop\QGIS\202504_LASTools\99_data\sample.las" ^
        -o "C:\Users\Lee\Desktop\QGIS\202504_LASTools\99_data\sample_ellipsoid.las" ^

        -geoid "C:\Users\Lee\Desktop\QGIS\202504_LASTools\tide\WMSL_IMSL_2018_fina_32.gtx" -v  

(run: Failed to execute las2las ... exit code: 2)

In both cases:

• The .gtx file fully covers the spatial extent of the input point cloud.

• The LAS files are generated from PDS-format hydrographic survey data acquired using a multibeam echo sounder, and the COPC LAZ files were created after post-processing in Agisoft Metashape.

• The files are readable and displayable in laslook.

Unfortunately, due to internal data security policy, we are unable to share the actual LAS or GTX files externally.

Could you please advise whether this issue might be related to:

• Known limitations in GTX application to COPC or bathymetric LAS?

• Specific header requirements or metadata structures?

We would greatly appreciate your help in resolving this issue.

  Additionally, I would like to mention that I tested the same las2las -geoid command using a LAS file acquired from an airborne LiDAR survey (not bathymetric or PDS-derived), but the result was the same — the tool returned the same error and failed to execute. As I am still new to LAStools and LiDAR processing in general, I relied heavily on ChatGPT to help construct the command syntax. I’m not entirely sure if the commands I used are fully correct, so I sincerely appreciate your guidance and understanding.  

Best regards,
HoSeok Lee

2025년 5월 23일 (금) 오후 3:15, LAStools - efficient tools for LiDAR processing <last...@googlegroups.com>님이 작성:

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