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Calculate difference in volume between 2 different time data sets

Hello, 

I want to know if I set GCP and measure (survey) them, fly the area (dirt pile) and process that.  At some point in the future, a client will do some more dirt work either adding or removing to the pile, if I refly it with GCP can I get pix to calculate the difference? 

Is there a workflow for that published somewhere?

 

Thanks

I saw some article about that already but I wanted to expand on this with: 

Does it make a difference if I cannot use permanent GCP points due to the area being changed too much. can I survey in new and different GCP each time to tie the data together?

Thanks

Hi, 

Probably you refer to this article on how to compute the volume difference: https://support.pix4d.com/hc/en-us/articles/202559189 

If you have two projects at two different moments in time of the same area. The workflow I usually recommend is to compute the volume of the area of interest in each of them and then calculate the difference, e.g. in an Excel sheet.

If the base surface of the volume remains the same and you add or remove some volume from the pile, a trick is to export the base surface in one project and import it in the second, so that the comparison is more accurate. This will avoid clicking errors. 

As for the GCPs, I think it is not an issue as long as you use GCPs in both projects. The accuracy of the reconstruction will be similar in both, as long as the GCPs are well distributed over the area and if possible close to the volume of interest. 

Maybe other Community users who compare volumes regularly can share their workflow and tips too. :) 

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