Height inconsistencies

I have a mission that follows a lateral grid scan of a wall, first set of waypoints is set up to be at an altitude of 15 m above the start area and the next set is up at 13.5m and so on. The problem is that the drone doesn’t seem to stick to the height specified on each waypoint as for example on the first set it was flying more or less correctly at 15 m but when it got back around this time at 13.5m it seemed both from looking at the drone itself and the video that the drone was way higher than 13.5m I would say at about 18-20m. The wind overall was within 24-26 km/h range. Can anyone explain what could have happened that the drone didn’t follow set up altitudes?

Do you recall what the height was that was displayed on the Litchi screen? When you say that the drone “doesn’t stick to the height specified” so you mean on subsequent flights or within the same mission?

Without completely understanding what you are describing, my guess would be that this was due to inaccuracies in height as determined by barometric pressure. The drone’s height above the take-off location is determined by barometric pressure. This is accurate up to a couple meters throughout the course of one flight.

Once we know if you are comparing two separate executions of the same waypoint mission or if you are comparing the heights of two separate waypoints within the same mission, we can provide a more direct answer.

To be specific I have a mission consisting of roughly 15 waypoints which are divided into 3 subsets, each has different height set up in the mission hub 15 m, 13.5m and 12m. Could such wind speeds of around 24-26 km/h really cause such a difference in barometric pressure throught the flight that the drone was way above it’s specified height? The reading in the app at the moment I noticed it to be way higher than I specified was at 13.5 m which is also puzzling. I am 100% sure that the drone was higher than it should have been judging from the video material as on the frames with height specified and read by the drone to be 15m I have seen only a portion of the building’s roof but on the frames with height specified and read to be 13.5m I have seen almost entirety of the roof and only a tiny fraction of the wall itself.

Wind should not directly cause the local barometric pressure to change which in turn would cause the heights to be off. The barometric pressure could change slightly over the course of flight of several minutes or more.

The key to solving this is to note what height Litchi is displaying as you fly through your waypoints. While pressure changes can cause the height to vary, Litchi should always fly the drone at (and display) the height configured for each waypoint. In other words, if you configure a waypoint to be 13.5 m, Litchi (or DJI Fly) should display a height very close to 13.5 m at that waypoint even though it is possible that your drone’s computed height of 13.5 m is inaccurate.

I understand that but it still doesn’t really answer the question what could’ve caused the drone to fly higher than it should and what was specified in the app at the given moment. My guess is that the drone got uplifted by the wind a little over the course of the flight and the app just didn’t seem to correct it’s height accordingly for some reason.

You have not directly answered it but it sounds like you are saying that the height Litchi displayed on the screen was significantly different from what you had configured for those waypoints.

The drone is what maintains its own height. The flight controller in the drone is what makes altitude corrections. You can test this yourself by setting your drone to hover at hand height. Then, carefully with one hand, gently push the drone up from underneath, or gently grasp the drone and pull down a little bit. You will find that the drone, by itself, adjusts its thrust to maintain a constant height.

I don’t know if I phrased my situation poorly or something but allow me to repeat myself, I have a mission set up that the drone flies parallel to a certain wall in a straight line, first set of 5 waypoints is set up to be flown at an altitude of 15m above the starting point, then on the second set of 5 waypoints the altitude I set up drops to 13.5m and the third set follows exactly the same pattern but now the altitude is set to be 12m. My issue is that after flying on the height of 15m and maintaining it pretty well throught the first 5 waypoints when the drone reaches waypoint 6 it seemed to have adjusted the altitude to be 13.5m but after it got back to the area of the starting point of the whole mission I noticed that it was flying significantly higher than those 13.5m I set up on the specific waypoint it was at. The readings on the app at the time were indeed stating that the drone was at 13.5m but it was a false reading in my opinion judging from the video footage captured during the mission and from the position of the drone itself I observed with my own eyes.

Share your mission and the flight log. Then, users here will be able to see much more clearly what the problem might be and make suggestions to correct it.