las2las

[Asif Miyan]

Hi all, 

I want to reproject a number of laz tiles to GDA2020 - Vicgrid using ausgeoid2020 as a Geoid model. The laz tiles are already on GDA2020 - Vicgrid but no geoid model. I had a look on las2las but cant see the epsg code 7899+5711 listed.  Looking for some guidance and help how to do it if anyone is aware?

Thjanks

[Jorge Delgado García]

Please, could you provide me any LAZ file in your original CRS in order to check to conversion. Perhaps, you need make it in two phases ... first into 7899 and second into 5711? But I need to check.

Could you provide one example of the coordinates of a point in both systems?

Jorge

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[Michael Perdue]

Hi Asif,

I'm not exactly sure what you are asking. Are you saying that you just need to reproject the files and insert the proper georeferencing info into the files? Or, does your data need to be reprojected into EPSG 7899 and have the elevations converted from ellipsoidal values to Orthometric values using the appropriate geoid (which is a vertical datum transformation)?

A couple of things.

1. las2las for the most part does not do datum conversions (Horizontal or Vertical). If your data is GDA2020 with ellipsoidal elevations, then you need to do a vertical datum transformation using the appropriate geoid. The appropriate tool for that task is lasvdatum or lasheight.
2. las2las is the appropriate tool for reprojection and to write the proper georeferencing info into the headers, but I just took a look at geoprojectionconverter.cpp and there is no mention of EPSG 5711. so I doubt lastools knows how to build the COMPOUNDCRS you are asking for. However, you can assign a custom ogc wkt string of your choosing with las2las and the (undocumented) switch '-load_ogc_wkt '. Check out the following thread for more details.

https://groups.google.com/g/lastools/c/UMwvFhC-_Qs/m/wDUYDjgzBAAJ

Cheers,

Mike

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