Volumetrics pix4d vs drone deploy

Munch520 · May 24, 2017

Hey guys, flew a mission two days ago (in DroneDeploy) about 9 acre area, 500 images or so, 80% overlap, 90deg camera angle) and am seeing a ~7% variance in a volumetric measurement between the two platforms (using same data set). Screen shots below...given that both these programs have the same photos and EXIF data, is this difference due to the difference in the way the programs interpret it? And then the question is obviously which one to trust?

32.88 cubic m (converted from 43.xx cubic yd)

35.25 cubic m

Thanks all!

Richard R · May 24, 2017

The answer to your first question is "Most likely!". Even with the same program, if you mark slightly different boundaries, you can get variations in the results. As far as which one to trust, I would say neither!! That is until you had some ground truth data with which to compare results. You can't assume that any program like this is giving accurate info until you have validated it. You shouldn't even use that fact that someone else has done so because, again, their procedures may be different from yours. In general though +-less than 5% sounds like pretty close agreement to me.

doktorinjh · May 24, 2017

Munch520 said:
is this difference due to the difference in the way the programs interpret it?

Yes, and you can read up on how Drone Deploy and Pix4D calculate volumes. As Richard also mentioned, there can be quite a bit of variability based on how you draw your boundaries around a stockpile. I recently did a test where I traced a stockpile about a dozen times to see how much variation I could expect and some of the largest outliers were about 6% different. I also saw an average error of about 2% from Pix4D's built-in error calculation. The stockpile I measured averaged 3500 cubic m, so your smaller pile may be more sensitive to different boundaries.