Global Shift/Scale

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RK123
Posts: 4
Joined: Thu Mar 15, 2018 6:54 pm

Global Shift/Scale

Post by RK123 »

Hello,

I have a question about the global shift/scale feature. I am using drone data for large point clouds (~100 acres). Is it still appropriate to use the global scale? I am looking for centimeter accuracy, not micron accuracy.

Do you always recommend shifting point clouds? I know an object a few meters wide and a large ground area are two different scenarios. In this case, how much precision is lost? Will I be able to keep cm accuracy? Again, I am not concerned about anything smaller than 0.001.

Thank you for sharing this great program with us, it's been really helpful!
PCEngineer
Posts: 5
Joined: Fri Feb 24, 2017 12:33 pm

Re: Global Shift/Scale

Post by PCEngineer »

Why would you not want to use the global shift and scale? I think it might improve the speed during operation and I don't see any negative effects?
daniel
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Re: Global Shift/Scale

Post by daniel »

Sorry @RK123, I thought I already replied to your question but apparently something went wrong...

While you should always use the global shift, I don't think it's necessary to use the global scale. The rule of thumb is that the dimensions of the cloud shouldn't be 10^7 bigger than the precision you are looking for. If you seek 10^-3, then the scale shouldn't be higher than 10^4 (should be fine in your case).

Does CC suggest to apply a global 'scale' in addition to a global 'shift'?
Daniel, CloudCompare admin
RK123
Posts: 4
Joined: Thu Mar 15, 2018 6:54 pm

Re: Global Shift/Scale

Post by RK123 »

Daniel,

Thanks for clarify the precision impact, that explanation helps.

CC has not suggested applying a scale, but I thought I would clarify both points if I was asking anyway.

Thanks again!!!
RK123
Posts: 4
Joined: Thu Mar 15, 2018 6:54 pm

Re: Global Shift/Scale

Post by RK123 »

For the record, the reason I would not want to use the global shift/scale feature is I have had trouble correctly displaying contours with this feature selected.

Thanks!
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