- The elevation shown in the accuracy report is based off the altitude of the drone mission. Example: in the mission you set the altitude at 100’ the photos will show 100’ as the altitude due to it only knows the elevation where it took off at was 0’. Now you can adjust the the elevation by calibrating the map (under Map Details) of a know elevation.
I use a RTK drone and a base station which allows me to set the base station up and it talks to the drone during the flight to give error corrections and altitude information, this information is then added to the photos. So instead of the the drone taking off at elevation 0’ it would tell the drone your at elevation say 152’ and you fly at altitude of 100’, the photo will show the elevation as 252’ in the exif data.
The overall accuracy depends on the drones camera and how you setup and flew the mission. Did you have enough overlap (front/side) was you altitude correct for the mission, the higher the flight the lower the resolution of accuracy, at 100’ altitude you can see a 1" object on the ground at 300’ you can see a 5" object on the ground. with the lower flight I can see the height better than I can at 300’.
Yes and no, it depends on your setup. If you use Ground Control Panels (GCPs) (with accurate survey data on each panel) then the accuracy will be really good, make sure you use enough GCPs.
If you are flying say a Phantom 4 and it takes 300 photos of a 100 Acre site then your Map won’t be accurate.
I currently fly a 150’ with 65% Side and 80% Front overlaps and I generally will get a 99%+ on map stitching and 15 to 20 Photos per pixel and get 14 to 16 images per GCP (16 is the max in the selection). I usually have 6 GCPs per site (I prefer more) when flying.
When I’m flying 400+ Acres I fly at 305’ with a 68% Side and 80% Front overlaps. Flying higher will see more per photo but because of that it would take less passes to complete the mission so I compensate by adding more Side lap which gives me more routes. This ensures I get all the data I need for the site and maintain the Photo to Pixel Ratio I like to have. Example I just drove 4 hrs to fly a 450 Ac site, it took 6 hrs to fly at 305’ with small overlaps of each mission ( I broke up the site into 5 separate missions) and before I left the site I took all the photos and did a Upload process to DroneDeploy so it would create a Blue Dot Map and that showed me that I did not have any holes in my coverage of the site.
So with all that said accuracy can be there as long as you plan properly and use the proper tools. I flew a 900+ Acres site last month for as part of site improvement survey and they used the Map as a backdrop for all the data the surveyors collected on the ground. It was cool to hear the Map aligned with what the surveyors captured on the ground.