Volume calculation

[Adam]

Hello,

I'm using the volume calculation to calculate volume loss.

If I change the step value, I keep having a different volume. what is the step stand for? what is the best value in the case below? thank you

Step value 2.000000
Volume: -27.029
Surface: 9,760.000
----------------------
Added volume: (+)114.202
Removed volume: (-)141.231
----------------------
Matching cells: 98.2%
Non-matching cells:
ground = 0.7%
ceil = 1.1%
Average neighbors per cell: 7.8 / 8.0

Step value 1.000000
Volume: -17.811
Surface: 9,486.000
----------------------
Added volume: (+)147.880
Removed volume: (-)165.691
----------------------
Matching cells: 97.5%
Non-matching cells:
ground = 0.9%
ceil = 1.6%
Average neighbors per cell: 7.9 / 8.0

Step value 0.5000000
Volume: -8.526
Surface: 9,368.250
----------------------
Added volume: (+)183.858
Removed volume: (-)192.384
----------------------
Matching cells: 97.4%
Non-matching cells:
ground = 1.1%
ceil = 1.5%
Average neighbors per cell: 7.9 / 8.0

[daniel]

The step value defines the resolution of the raster grid that is used to estimate the volume.

The coarser / bigger it is, the less accurate the result will be. Therefore you should aim for the smallest step possible. However, you will be limited by the density of your clouds. Pay attention to the average neigbors per cell percentage. It should stay close to 8 otherwise it means that holes are appearing between the cells and it will give a wrong volume estimate.

[Adam]

Thanks for your reply. I always get Average neighbours per cell: 7.9 / 8 or 7.8/8. Does it mean I'm on the safe side?
How about Matching cells percentage? the higher the better and does this mean CC found the same cells on both clouds?
I also have posted a topic about M3C2 parameters in the question thread, there are some questions please look at them

[daniel]

Yes 7.8 is still safe.

And regarding the matching cells percentage, it's indeed the number of cells that have a matching cell in the other grid. However it only indicates how well the two clouds overlap. There's no particular reason to use it as a criteria when changing the step size.

[anagellerramser]

Hi Adam, I am trying to do something similar, but I want to calculate the volume of plant that I lost, could you tell me if this tool worked for you? How you exported the volume information?

[DA523]

It worked for me in serveral shapes...
You mean export volume result in text or result volume as pointscloud?
Can you share 2 pc as example

[anagellerramser]

Thank you for answering.

Ok, so, I'll try to explain better. I have two point clouds, one represents my plot of soybeans before cutting, and the other after having cut 6ft of soybeans, I'm trying to calculate the volume of this "hole" (part in red in the image) left by the cut comparing the two clouds, however with the volume tool, the exported cloud is the height difference tool, the tool only gives the volume value in the box, I'm trying to export the volume information to Excel, or another program. I transformed this height cloud into a raster and imported it into Qgis to calculate the volume, but I'm also unsure about the size of the step, how did you choose the value of this parameter? And how did you get the final volume information? I have 2,000 clouds to calculate.
Another thing that is weird is that the relative height scalar says the red part is 18, maybe centimeters, compared to the ground, but the soybeans were bigger than this.

[DA523]

Use leave it empty otherwise you can get wrong results
..

e.png (14.63 KiB) Viewed 11156 times

..
Start with small grid then increase until shape of grid is regular and volume is stable

..

1.png (40.71 KiB) Viewed 11156 times

This is OK

2.png (54.76 KiB) Viewed 11156 times

This is not OK because alot of holes , grid is too small compared to cloud density
..

You can check attached file for easy testing

volume.zip

(188.84 KiB) Downloaded 280 times

[DA523]

I have 2,000 clouds to calculate.

I am not sure about CC command line to calculate volume ??
but the hard way but efficient is to use Windows batch file and AutoHotKey free software to automate volume calculation and saving etc ...

[anagellerramser]

Got it, thank you for your help.