Hi, A relative level error has come to light with a survey iv just carried out.
I have flown the stockyard of the mine I work at with DJI Phantom 4 Pro. I used DroneDeploy to do the flight @ 100m above ground. I used 6 GCP surveyed in with RTK GPS.
The survey was also carried out with the RTK GPS on foot the old fashioned way to check.
The problem I have found is the base of all the stocks is about 600mm higher than it should be when compared to the on foot survey (and some known ground levels). The tops of the stock piles are not bad but a little above where they should be.
The overall GCP error was 75mm and none of the GCP stations was more then 120mm different from where it was surveyed.
Iv done a similar survey before with no problems.
Any ideas what the likely cause is?