What does interpolate mean?

Emil Cost · Jun 8, 2016

Hi everybody. I own a Phantom 3 Advanced. I think this is my first post. I am using the Litchi app and have had success planning and executing a few simple missions. I have a couple of questions that I could probably answer with experimentation, but I'll ask here to save a little time, and to practice asking questions with this fine forum as well. So here are my two questions, presented in conditions, followed by the question.

1. Way point 1 gimbal pitch set to Focus POI #1
2. Way point 2 gimbal pitch set to Focus POI #2

Question #1: Will the gimbal transition from POI 1 to POI 2 happen gradually, or will the gimbal transition to POI 2 happen once the Phantom reaches way point 2?

Question #2: If the gimbal transition occurs gradually between two way points, then what is the effect of choosing interpolate, instead of Focus POI?

Thank you very much. this forum is really great!

Wolfiesden · Jun 8, 2016

Help - Litchi

Gimbal Pitch: Choose between "Disabled" where the gimbal pitch control will be manual, "Focus POI" where Litchi will automatically control the gimbal pitch to keep the selected POI in the center of the frame (blue markers), or "Interpolate" where you can specify the gimbal pitch angle at this waypoint. For "Interpolate" to work, the previous or next waypoint need to be set to "Interpolate" as well. Litchi will then automatically adjust the gimbal pitch angle to start and end at the specified angles, and smoothly transition while travelling between the two waypoints.

Question #1: Gradually over the distance between the WP markers. The closer they are, the more rapid the transition.

Question #2:
When the WP specifies POI for the gimbal angle, the altitude of the aircraft, the distance from the POI and the altitude of the POI are calculated together to form the correct gimbal angle so it points directly at the POI. Lets say your AC is at 300'AGL and your POI is set for 100'AGL (a difference of 200') and the AC is 200' away from the POI. The gimbal must point down at 45deg so that its aimed at a point in space 200' below it and 200' away. The effect in video is that the POI (including altitude) will remain centered in the frame as the aircraft flies the course.

Choosing interpolate is a different option and the effect is different. Yes, the aircraft will still yaw to point at the POI as set in the waypoint directive, however the gimbal will pitch up/down to a specific angle you set. Lets say you set it for 75deg. As the AC transitions from WP1 to WP2 the gimbal (and video) will appear to pan from the POI down to what might be its base while still keeping it horizontally centered in the frame. At WP2 the gimbal would be pointed down at 75deg instead of being pointed at the altitude the POI specified but the AC's yaw will still point directly at the POI.

Emil Cost · Jun 8, 2016

Wolfiesden said:
Help - Litchi

Question #1: Gradually over the distance between the WP markers. The closer they are, the more rapid the transition.

Question #2:
When the WP specifies POI for the gimbal angle, the altitude of the aircraft, the distance from the POI and the altitude of the POI are calculated together to form the correct gimbal angle so it points directly at the POI. Lets say your AC is at 300'AGL and your POI is set for 100'AGL (a difference of 200') and the AC is 200' away from the POI. The gimbal must point down at 45deg so that its aimed at a point in space 200' below it and 200' away. The effect in video is that the POI (including altitude) will remain centered in the frame as the aircraft flies the course.

Choosing interpolate is a different option and the effect is different. Yes, the aircraft will still yaw to point at the POI as set in the waypoint directive, however the gimbal will pitch up/down to a specific angle you set. Lets say you set it for 75deg. As the AC transitions from WP1 to WP2 the gimbal (and video) will appear to pan from the POI down to what might be its base while still keeping it horizontally centered in the frame. At WP2 the gimbal would be pointed down at 75deg instead of being pointed at the altitude the POI specified but the AC's yaw will still point directly at the POI.