been pulling my hair out over this one. did a survey flight for a small construction site, 80/75 overlap, flew at 60m AGL, used 5 GCPs with a decent RTK GPS unit (not the cheapest but not a leica either), processed in DroneDeploy and the accuracy report looked solid. sub-5cm horizontal, vertical was a little higher maybe 7cm but thats within what i told them to expect

client comes back saying their measurements from the model dont match what their ground crew is getting and the discrepancy is like 15-20cm in some spots which is way outside what the report shows. i went back and checked my GCP placement and they looked fine in the software, checkmarks all green basically

not sure if this is a me problem or a them problem at this point. is there something about how DroneDeploy reports accuracy that im maybe misunderstanding, or could this be a coordinate system thing? the site is in a weird area and i did have to do some manual CRS stuff when setting up the project

coordinate system issue almost guaranteed. this exact thing happened to me on a job near the coast where there was some local datum weirdness and the software was technically accurate within its own reference frame but the client was measuring against a different baseline. what CRS did you set the project to and what is the ground crew using for their total station or GPS? if theres any mismatch there you can get exactly the kind of systematic offset youre describing especially if its consistent across the site rather than random

also worth checking if DroneDeploy applied any geoid model to the vertical ? sometimes it defaults to ellipsoidal height and if the client is expecting orthometric heights thats another place it can go sideways on you

yeah the accuracy report being green doesnt always tell the whole story tbh, those numbers are residuals at the GCP locations which doesnt necessarily mean the whole model is accurate everywhere. if your GCPs were all clustered in one part of the site you can get good numbers there but the model warps toward the edges. how spread out were your control points across the site area