Waypoint Missions in DJI Fly - Setting POI Altitudes vs Waypoint Altitudes on the RC-2

[Squidinc]

I've recently started experimenting with setting up way point flights on my RC-2 controller in advance of actually flying. A wonderful and exciting option that can be done anywhere in the world.

Today I was flying one of these pre-planned flights, and came across an unexpected issue flying over the ocean to my first POI. My first waypoint was set at 20 metres, and the POI was set at 5 metres. The drone set off to waypoint one at 20 metres and all was well. Suddenly as my Air 3 approached the first POI the drone started losing altitude. When it fell to 5 metres I hit pause stopping the mission as it felt like it was heading for the ocean. I hit the "pause" button and returned to home.

What I realised was that the POI needs to be set at equal to or above the waypoint altitude. If the POI is less than the waypoint on approach the drone will descend to the POI altitude. Very unnerving to say the least. Nothing in the manual about this that I could find.

 

[mobilehomer]

No, the POI does NOT need to be set equal or above the WP altitude. I do this quite often. The waypoint algorithm DJI employs uses Bezier curves in both horizontal and vertical planes. Was the second WP altitude different from the first?

 

[Droning on and on...]

@mobilehomer is correct. There's something else amiss here.

POI height only affects the camera gimbal tilt to center that point in space (POI height and location) in the camera frame.

@Squidinc, as always if you can pull the logs off the RC2, and either post it here, or even better upload to @msinger's log viewer and post the link maybe the MPDC braintrust can figure out what happened.

 

[DJ Wes]

Today I was flying one of these pre-planned flights, and came across an unexpected issue flying over the ocean to my first POI. My first waypoint was set at 20 metres, and the POI was set at 5 metres. The drone set off to waypoint one at 20 metres and all was well. Suddenly as my Air 3 approached the first POI the drone started losing altitude. When it fell to 5 metres I hit pause stopping the mission as it felt like it was heading for the ocean. I hit the "pause" button and returned to home.

What I realised was that the POI needs to be set at equal to or above the waypoint altitude. If the POI is less than the waypoint on approach the drone will descend to the POI altitude. Very unnerving to say the least. Nothing in the manual about this that I could find.

I may know what is happening but I would need to see your mission to be sure. First, some clarifications. Perhaps you erroneously swapped some terms, but your drone does not fly to a "POI". Instead, it only flies to and through "waypoints". In any case, a POI is irrelevant to the flight path defined by waypoints.

One of the characteristics of the type of curve (spline) that DJI uses is that it passes through each waypoint. Therefore, it does not have the "convex hull" property. This means that the flight path can exist outside the boundaries of straight lines connecting the waypoints. To understand what I mean, see the image below. It contains several waypoints connected by a couple different types of splines.

If such a mission was designed in primarily the vertical plane, notice how the flight path (spline) dips below the height of the first two waypoints. Again, this is just a guess, but if your waypoints were configured in such a way as to create a significant change in altitude, it my cause the flight path to travel below the height of one or more of your waypoints. If you were to share your mission, I could tell you for sure.