I have 2 sets of data generated from 3D laser scanner in the field. The period between the data is around 8 months. I would like to compare the 2 (before and after), so I would like to see the differences in the surface (if there are any loss in the surface for example). I have saved the data as Ply then imported into CC. The 2 scans are on top of each other when I import the data into CC. However, the scans are slightly different (where one of them is bigger than the other. I could trim them to make them closer but they will not be exactly the same. I have used the command ''sample points on a mesh''. Then I have highlighted the 2 clouds and register them by ''align 2 clouds by picking''. I can find mutual points from the 2 scans, so I picked them as reference points. Then I have applied the ICP for fine registration (I used overlap as 80%, RMS left the same, no adjust scale, no enable farthest points removal and I have increased the random sampling points to 2000000 more than the data and model. after using ''align points pair picking''. The RMS get smaller which I assume the smaller RMS the better is the registration.
1/Which one to use to see the difference between the 2 scans? M3C2 or compute cloud to cloud distance (C2C)?
2/What is volume calculation will tell me? does it tell me the loss volume? how accurate is this if the 2 scans are not 100% the same size. Maybe the volume will increase because the second scan is slightly bigger? Empty cells, I usually use leave empty and leave the step as 1.000000 and cell height as average.
3/I'm not sure what to sue in the M3C2 distance settings like the main para..normals I normally leaving them as they are with ticking the box of the standard deviation and point density in the output.
4/ I want to able to present the 2 scans and say this what has changed
5/ The standards deviation of M3C2 and C2C are very similar but the means are different. I also want to look at the standard deviation for both scans separately. I do get STD_cloud1 and STD_cloud2. Are these the standard deviations for cloud1 (scan 1, reference) and (scan 2, registered). Do they represent the roughness? because there is another roughness in the toolbar under ''other'' but I'm not sure whether to leave the Kernel size the same or not as both clouds have a different value
6/If I use C2C there will blue colour with some yellow-red. Are these colour represent the difference from the first scan?
7/ I use Surfer software to get a nice contour map for surface visualization. I import the M3C2 file in ASCII format to surfer to look at the height differences between the 2 scans.
I also have another site where I scanned the same area but the scanner wasn't exactly at the same angle. See image 4. In this case is it possible to carry on with analysis?
Here are some pics! How can I upload CC file here? sorry for all these questions! I'm writing a conference paper and I need to put all these analyses.
- Capture4.PNG (85.59 KiB) Viewed 226 times
- Capture1.PNG (137.45 KiB) Viewed 226 times
- Capture2.PNG (196.57 KiB) Viewed 226 times