Preserving global shift on save for LAS

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Unagna
Posts: 2
Joined: Fri Sep 13, 2024 10:59 am

Preserving global shift on save for LAS

Post by Unagna »

Hi,
I have a georeferenced cloud (dimensions: 600x250 meters). When I import it in CC, it suggests to shift the coordinates.
Original coordinates are:
X = 608056.9158
Y = 4839923.8915
Z = 84.265100
I chose to shift the cloud as the local coordinates will be X=0, Y=0 and Z=0.

If I check the option "Preserve global shift on save", when I export the model in LAS, I suppose it should remain X=0, Y=0 and Z=0 but I get these new coordinate system instead:
X=-137.508301
Y=-307.876007
Z=-35.828999
If I uncheck the option "Preserve global shift on save", when I export the model, I should get the original coordinates but I get these new ones instead:
X=607919.375000
Y=4839616.00
Z=48.431
I can't understand why and I am more puzzled because if I sum the preserved coordinates and the unpreserved ones, I get the actual original coordinates?

Thanks in advance to anyone who will help me solve the issue.
daniel
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Location: Grenoble, France
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Re: Preserving global shift on save for LAS

Post by daniel »

Yes, it's similar to this post: viewtopic.php?p=30162#p30162

If the cloud was coming from a LAS file, CC was choosing the original 'LAS offset' information by default at the time of saving. The global shift is potentially different and it's only temporary in CC, so we didn't want to overwrite the original LAS offset which can be important for some users.

The latest 2.14.alpha version now lets the user choose which offset to use as 'LAS offset' in the LAS save dialog. And the default offset should be a little bit smarter hopefully (I now assume that if the Global Shift is different from the LAS offset in the XY plane, then it means that the user really wanted to change it and it's not involuntary).

You can test it, it's now online.
Daniel, CloudCompare admin
Unagna
Posts: 2
Joined: Fri Sep 13, 2024 10:59 am

Re: Preserving global shift on save for LAS

Post by Unagna »

Thank you, I will try!
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