Using lasvdatum to change vertical datum without intermediate files

[jean.franc...@gmail.com]

Hi,

I have data using the CGVD2013 height model that I want to transform to the CGVD28 height model. Having GTX files for both, I currently do:

lasvdatum64 -i cgvd2013\*.laz -vgrid CGVD2013.gtx - backward -odir ellipsoid -olaz

lasvdatum64 -i  ellipsoid\*.laz -vgrid CGVD28.gtx -odir cgvd28 -olaz

It's fine, it works, but could I avoid the temporary files?

Thanks!

[Michael Perdue]

The easiest way is to difference your geoids with GDAL. Something like:
gdal_calc.py -A geoid_a.gtx -B geoid_b.gtx -calc="A-B" --outfile diff_A_B.gtx

Then you just run it through lasvdatum with the difference geoid as normal and your done in a single move. Just watch your sign and make sure your apply it the correct direction. It's easy to get wrong and subtle in the magnitude of the mistake.

Mike

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[rapid...@gmail.com]

Hi Jean Francois,

to avoid temporary files you can also use LAStools with pipes (stdout/stdin): 

Something like

    lasvdatum64 -i cgvd2013\*.laz -vgrid CGVD2013.gtx - backward -stdout | lasvdatum64 -stdin -vgrid CGVD28.gtx -odir cgvd28 -olaz

should work.

Cheers,

Jochen @rapidlasso