lasvdatum, epsg codes and proj geodetic database

[Wes Toews]

Hello and happy new year!

1) The lasvdatum tool is great. It takes an -epsg argument to be able to transform points back into geographic coordinates. Since the proj4 integration with las2las, is it (or will it be) possible to specify like a -proj_epsg code and use that mechanism for coordinate transformation? Just to ensure consistency.

2) Related, proj4 has published geodetic tiff grids (Geodetic TIFF grids (GTG) — PROJ 9.7.1 documentation) and a CDN (PROJ Datumgrid CDN) of these grids. lasvdatum currently uses GTX. Is it possible to upgrade to taking these tiffs? Probably constrained by VERTICAL_OFFSET_GEOGRAPHIC_TO_VERTICAL tag or the band description "geoid_undulation" or something. Converting from tif -> gtx is fine, but using GDAL, I sometimes needed to add -unscale -ot Float32 in order for the GTX to be correct (just the first thing I discovered, there are probably more issues). I'm sure there's a reason for GTX, so I guess I'm expecting to be corrected here.

Thanks!

[Jochen Rapidlasso]

Happy New Year to all LAStools users and friends!

About your questions: PROJ is only available at las2las64 right now. Using las2las64 with PROJ arguments means that you give away the conversion to PROJ. If you define a conversion where PROJ have to use a grid (or is configured that way) it should work with all kinds of grids PROJ is able to use. All this is done on PROJ side. If this does not work as you expect please define a small but complete sample and we will try to help.

Cheers,

Jochen @rapidlasso