I’m seeking opinions and experiences from traditional theodolite & other ground based surveyors who’ve moved on to drone mapping and structure from motion volume calculations. In my experience, I’m getting 2-4% differences between theodolite transect volumes (admittedly a single slice of the landscape) and Pix4D volume calculations from drone aerial mapping (which also gives me ability to get 3d volumes of entire landscape elements). So, my question is: how much variability or “error” is acceptable in traditional theodolite mapping? Do you agree that the future of open area landscape mapping is NOT ground based, but better done from on high (drone or LiDAR), etc.
Please let me know your thoughts.
In my opinion we are already there. The important part is to continue to ground truth the data and understand the limitations. LIDAR and Photogrammetry are very different applications.
Thanks for. Replying jl
Still, I’m searching for what is acceptable “error” or variability in theodolite vs photogrammetry? If I pay for a truckload (assuming it’s weight is the key) of sand or such, and after its dumped and moved around, can I measure the volume precisely enough to match what I know was once in the truck? What % of the true load is acceptable as measured by photogrammetry?
I think 5%
Hi Graves,
Sorry for the late reply by I am a newbie to the Pix4D community. I am trying to incorporate UAV mapping into our current workflow. When I started surveying around 35 years ago we were still using a chain and transit.
We do a lot of construction surveying and most of the contractors pay by the truckload using volume, not weight. On big import / export projects they have someone collecting tickets from the drivers and pay by the ticket (truckload).
And if you are calculating volumes then you first have to measure what is existing first, then when fill is placed, or cut is removed, you have a baseline to compare.
As far as your differences you are definitely going to be more accurate with your UAV, as long as your information has been gathered correctly. When a field crew gathers data they measure what they think are “key” points. The bottom and tops of piles, maybe a few spots in between. With aerial mapping data you get it all.
And back to the “dirt”… if the material is something like base for a roadway the compaction will change the volume dramatically. If the fill is for landscaping beds it is barely compacted. So I guess the easy answer is there is no easy answer.
But as jl said make sure you always use quality control on your data, the first time you don’t it will bite you.