There was a request to check for an error on lascopy.
Due this happen may to other users and to have it documented
here a small post about the issue.
The challenge was to join 2 point clouds:
The first file got (almost) all.
The second file got the classification of some points to classify them as buildings.
The command was
lascopy.exe -i only_buildings.laz -i everything.laz -classification -o result.las
The result is like this:
As you see there are some wrong classifications:
So the result was not as expected and had those "ghost" buildings within somewhere.
Analysis of the data show, that the source GPS timestamp in the source is not unique.
This is a problem - due lascopy use ONLY the timestamp to match the second input
with the first input points.
Suggestion of the user was to extend the match function to give more match options.
E.g. match only if also [ XYZ | scanner_channel | number_of_return ] match.
This would be possible, but it will
- slow down the show.
- consume a lot of memory.
- take quite a bit of my time.
Therefore I was looking for another solution.
My first suggestion would have been:
Try to keep the data clean.
If you think you need to have multiple identical timestamps in your data
try to keep them identifiable.
Then you have the option to LASsplit them.
Do the classification only on the suitable set of data.
Merge the data again.
In our case the data are mixed up somehow and I did not see a point to separate them.
Anyway, the LAStools are hopefully powerful enough to solve the problem.
This is what I did:
a) Merge the data, put the most wanted data in front:
lasmerge64.exe -i only_buildings.laz -i everything.laz -o work.laz
b) Remove the duplicates:
lasduplicate64.exe -i work.laz -o result.laz
The results seem reasonable to me.
Please let me know if there is something wrong in my thinking.
If there is a huge demand of extend lascopy just let me know.