Tracking a POI
Why isn't a POI tracked perfectly by the drone's heading?
When a POI is associated with a waypoint, Litchi sets the appropriate heading at that waypoint to point at the POI. In a mission where one POI is associated with two adjacent waypoints, the heading at each waypoint is set to point at the POI. This is easily seen in Litchi's Mission Hub. As the drone flies from the first waypoint to the next, the heading is linearly interpolated from the value defined at the first waypoint to the value defined at the next waypoint. This works well for cases where the POI is a similar distance from both waypoints. However, in certain cases, this method yields less than perfect results.
In extreme cases, where two waypoints are associated with the same POI and one waypoint is much closer to that POI than the other, the interpolated heading will cause the view of the drone to wander off of the POI as the drone travels from one waypoint to the next. In the figure to the right, the drone will correctly point at the POI at waypoints 1 and 2. However, midway between the two waypoints, the interpolated heading will not point at the POI. The solution is doing either of the following:
- Position waypoints pointing to the same POI roughly equal distances from that POI.
- Insert additional waypoints between waypoints 1 and 2 to help keep the focus on the POI
There is an exception to what is described above. "Hotpoint Mode" is used if all of the following conditions are met:
- The drone has native waypoints supported in the firmware (Mavic 2 Pro/Zoom and older).
- The mission has only one POI.
- All waypoints in the mission are associated with that one POI.
If the above three conditions are true, the DJI firmware employs something called "Hotpoint Mode" where the firmware does all of the heading calculations to keep the drone pointed at the POI. References:
Why isn't a POI tracked perfectly by the drone's gimbal pitch angle?
When a POI is associated with a waypoint and the Gimbal Pitch is set to "Point of Interest", Litchi sets the appropriate gimbal pitch angles at that waypoint to point at the POI. In a mission where one POI is associated with two adjacent waypoints, the gimbal pitch angle at each waypoint is set to point at the POI. This is easily seen in Litchi's Mission Hub. As the drone flies from the first waypoint to the next, the pitch angle is linearly interpolated from the value defined at the first waypoint to the value defined at the next waypoint. This works well for most cases. However, in extreme cases where the path between waypoints goes over the POI being tracked, the POI will not be tracked properly.
In this case, where two waypoints are associated with the same POI and the path between these waypoints goes over the POI, the interpolated gimbal pitch will not point down while over the POI between the two waypoints. In the figure to the right, the drone will correctly point at the POI at waypoints 1 and 2 where, in this example the gimbal pitch angle at each waypoint is -36°. However, midway between the two waypoints, the interpolated gimbal pitch angle will still be -36° and not point down at the POI. The solution is to do the following:
- Insert an additional waypoint between waypoints 1 and 2 near the POI to keep the focus on the POI.
There is an exception to what is described above. "Hotpoint Mode" is used if all of the following conditions are met:
- The drone has native waypoints supported in the firmware (Mavic 2 Pro/Zoom and older).
- The mission has only one POI.
- All waypoints in the mission are associated with that one POI.
If the above three conditions are true, the DJI firmware employs something called "Hotpoint Mode" where the firmware does all of the gimbal pitch calculations to keep the drone pointed at the POI. References: