how to register uneven/different areas (that contain equal areas)

[andre]

I am loading two .las files (20 to 22milion points each)
the area covered is different , one file covers more, the other less
They appear to overlap perfectly, I cannot verify Z , but X,Y looks perfect.

RED=There are excavated areas , supposed to be calculated for volume
GREEN=very different coverage in the different LAS files, some cover more, some less
BLUE=common ground to be used to register and correct Z if needed.

Screenshot from 2017-03-08 18-53-32.jpg (55.28 KiB) Viewed 1931 times

If I just select both .LAS , and click "finely registers rougly aligned..." with default settings, the result is no good, clearly misaligned in X,Y (and most likely in Z)

How can I make it align just in (unchanged areas) - and how can I undo bad registration ?

[daniel]

You have to set the 'final overlap' parameter right. And this corresponds to the percentage of points in the aligned cloud that have effectively an equivalent in the other cloud. This means that you have to discard the non overlapping areas (green), but also the excavated ones (red).

In effect, no need to be perfectly accurate, +/-10% is acceptable (e.g. 30% or 40% here?).

It's also generally better to use the widest cloud as reference.

[andre]

Hi, I am not sure what you mean by "This means that you have to discard the non overlapping areas (green), but also the excavated ones (red)."
Am I supposed to actually do something, like masking out some areas ?

Anyway - I just reduced the "final overlap" to 30% , and the result looks very good ! - kind of too simple.
Thank you.

[daniel]

I only meant that you have to discard these points in the evaluation of the 'population' of overlapping points ;)

So you simply had to reduce the 'overlap' parameter ;)