CloudCompare forum

Hi,

Just wondering, when you have the C2M distance computed, and the colour scale on the right showing the distances - what measurements are these? Are they in cm? Or does it depend on what cloud/mesh you are using. ATM, my clouds/mesh do not come with a measurement, they have been created through photographs, so I think are in pixels?
I am trying to determine the difference between 2 clouds/mesh so that I can see the change, so would like to be able to say "it has changed by ?cm over 6 months"
Is this possible?

Thanks!

Well, CC can't know better than yourself what the units of your entities are.

So indeed, it depends on your cloud/mesh: the distances are measured in the same units as your entities (it's what we call politely 'implicit units' ;).

Worst for you, photogrammetry is a scale-less method. The output cloud dimensions are not even expressed in pixels (they are generally the result of on an arbitrary scale used during the mathematical reconstruction process). You have to use external means to 'scale' your clouds (e.g. use the length of a known object visible in your clouds such as a scale bar, etc.). Some photogrammetry softwares may provide tools or specific methods to properly scale their output clouds.

Okay, thanks.
If I have a scale to the size of my cloud, so I know that they are 10/10cm, does this help in creating a measurement?

Well if you can measure the actual "distance" (unitless) between two points (with the Point Picking Tool for instance), you should then be able to find the right scale factor to convert your cloud in cms (simply use the 'Edit > Scale' tool to do that). Once that's done, all your measures will be in cms.