If you plan to fly a survey of a site with a mission height below 260ft (80m), you will need to make changes to your other mission settings in order to produce usable data.
The absolute minimum mission height the Phantom 4 RTK can fly is 82ft (25m). A mission height of 25m gives a ground sample distance (GSD) of 0.68cm/pixel, which is very high resolution.
However, we don't recommend flying any lower than 120ft (36m), unless airspace restrictions or other situational factors require a lower mission height.
When your mission height is restricted by airspace, plan a buffer of at least 1m below the ceiling. For example, if the flight ceiling is 100ft, you should fly at 98ft.
Increase the overlap to at least 80% both front and side. The lower the mission height, the higher the overlap rate should be.
By increasing the overlap, you are far less likely to have holes in the final model of your site. Increasing the overlap will increase the mission time, so be prepared to change batteries during the mission.
Note: to get high-accuracy PPK geotags, you must have at least 10 minutes of mission time per battery.
Flying close to the ground means that you are far more susceptible to motion blur. Therefore, you should decrease the speed of the drone.
Decreasing the speed is important beyond image quality. Because there are more obstacles when you fly closer to the ground, you should fly with more caution. Furthermore, your Visual Line of Sight (VLOS) may be compromised when flying low.
Try to take off from the highest point on the site. This helps prevent holes in your final model and ensure you have VLOS to your drone.
You should not need to change any other mission settings when flying at low heights.
I still can't do it!
We wrote these articles to arm you with everything you need to get the job done on your own, but we understand that sometimes this isn't sufficient.
If you're stuck, the Propeller tech support team may be able to help. You can contact our support team by emailing firstname.lastname@example.org.