Can LAStools difference two datasets?

[JK]

Hi,
I am new to LAStools...
Is it possible to difference two data sets on two different datums
that cover the same area?
I want to subtract one from the other to check if the result is as
expected.

Thanks,
Jess

[Martin Isenburg]

Hi,

here the summary of an off-line discussion with Jessica. To clarify
her needs she wrote: "I have two LAS data sets from exactly the same
collection that have been output to two different datums by the data
provider. One is on the ellipsoid and one is orthometric. I want to
subtract the ellipsoidal data set from the orthometric one to check
that the result is the geoid.". Later she sent me two LAS files with
the note "Attached are 2 of the LAS files that I would like to
difference. They should be roughly 8m apart in height. I would like
the differences reported as a third LAS file with the Z values being
the difference."

So I added the capability to lasdiff to create a LAS file of height
differences:

lasdiff.exe -i e303n5996_1m.las -i e303n5996_geoid_1m.las -o diff.las
lasinfo -i diff.las

and indeed ... lasinfo showed that there was a uniform distance of
7.78 to 7.79 meters in height between the two LAS files.

Jessica's final response was: "Thank you very much! That is fantastic!
We are researching vertical datum harmonization of topo and bathy DEMs
in the coastal zone for Australia. Our first step is to ensure data
providers are correctly supplying LiDAR data on the ellipsoid so this
tool is very useful."

Regards,

Martin @lastools