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Providing the Precision and Accuracy of Stockpile Volume Measurements
Hey everyone,
I’ve got a question about surveying and photogrammetry and I’m hoping someone here can help me out. My knowledge in land surveying is a bit out of date – I took a couple of courses a few years back and have been more into GIS stuff since then. So, I might get a few things wrong and I’m sorry about that in advance. We’re thinking about using drones and photogrammetry for measuring stockpile volumes at my company, instead of getting survey companies to do it. I’m trying to figure out how accurate and precise our results would be.
Right now, I’m using a Trimble R8 receiver with a CORS network for collecting RTK checkpoints. The standard deviation for these points averages around 0.025m horizontally and 0.04m vertically. I’m wondering if I should be using the 95% confidence interval instead of the usual 68% they give us for precision? Also, am I correct in assuming that because we are only calculating volumes we need to worry to about absolute accuracy?
Next, I do a drone flight with a PPK solution. In post processing I compare the differences in distance/elevation between our RTK checkpoints and the drone checkpoints, and this gives me an error of about sigma 0.006m in X/Y and sigma 0.015cm in Z. Should I be mixing these standard deviations to work out how much the volume might vary? Is this even the right way to do it?
Also, how should I present the accuracy of what I’m measuring? We will still have licensed surveyors surveying stockpiles whose values I can compare to, but they only give the estimated volume in cubic meters, without any precision or accuracy details. Any advice would be awesome. Thanks a lot!
Also: I think most of the time I’ll be doing these measurements without any specific base elevation values for the stockpiles. I’m basically assuming that the ground is flat. I’m planning to use PIX4D and its algorithms to calculate the cut and fill, relying on their automatically calculated base height.
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