Litchi Mission any variance between P3s and P4s?

[LZJ]

Wondering if any one has noticed any difference with running the same Litchi mission with different birds? Specifically a P3 SE and a P4P, i.e. a P4p with OAS running and no issues but a P3 running the mission hitting a tree, altitude deltas, speed limits, battery life, or other issues?

 

[Meta4]

Wondering if any one has noticed any difference with running the same Litchi mission with different birds? Specifically a P3 SE and a P4P, i.e. a P4p with OAS running and no issues but a P3 running the mission hitting a tree, altitude deltas, speed limits, battery life, or other issues?

There shouldn't be any significant differences running the same mission with either drone.
The mission has the same points, heights and speeds already set.
But you always need to allow for the variable inaccuracy of GPS and avoid setting the flight path too close to trees or other obstacles.
Even with the same drone, on successive flights, it could be +/- 10 feet or even a little more.

Are you asking about an incident that has happened, or wondering what might happen?

 

[LZJ]

I'm considering using a p4p with obstacle avoidance as a trail blazer to fly a technically difficult first part of a Litchi mission and if successful would then like to use a p3SE to extend that mission beyond the difficult part for a longer round trip. For whatever reason I seem to get longer flight times with the p3SE then I do with the p4p. Thanks

 

[Billie Nelson]

I'm considering using a p4p with obstacle avoidance as a trail blazer to fly a technically difficult first part of a Litchi mission and if successful would then like to use a p3SE to extend that mission beyond the difficult part for a longer round trip. For whatever reason I seem to get longer flight times with the p3SE then I do with the p4p. Thanks

This is a very good idea. Using a drone with obstacle avoidance to test fly a newly programmed Litchi mission will ensure that no collisions occur due to Litchi's sometimes inaccurate altitude measurements.

By way of example, I had become complacent flying my old Phantom3 Standard for well over 2 thousand miles of Litchi autonomous missions, and that casual attitude led me to believe that my usual programmed altitude of 150 feet AGL was adequate throughout the rural area in which I reside and fly the Phantom.

Purely on a whim, I flew a brand new untested Litchi mission not with the old Phantom 3S, but with my Mavic Pro1, which turned out to be the saving grace without which my Phantom would have surely gone AWOL under mysterious circumstances.

The Mavic Pro1 flew that programmed mission out way beyond signal range as is permissible where I live, and it was only later when I replayed the footage that I saw that the Mavic Pro, flying at what I thought to be 150 feet AGL, was in actuality flying way lower, and ultimately wound up on a collision course with a palm tree, at which point obstacle avoidance kicked in, causing the drone to swivel round and head straight to the launch point. Turns out that Litchi under-estimates altitudes whenever the launch point lies at a lower elevation than the course to be flown, with an error margin that can reach as much as a whopping 50 feet.

So your idea of running preliminary test flights with your Phantom4 is a very wise precaution for sure, before you fly a "blind" drone along the same route.

 

[LZJ]

This is a very good idea. Using a drone with obstacle avoidance to test fly a newly programmed Litchi mission will ensure that no collisions occur due to Litchi's sometimes inaccurate altitude measurements.

By way of example, I had become complacent flying my old Phantom3 Standard for well over 2 thousand miles of Litchi autonomous missions, and that casual attitude led me to believe that my usual programmed altitude of 150 feet AGL was adequate throughout the rural area in which I reside and fly the Phantom.

Purely on a whim, I flew a brand new untested Litchi mission not with the old Phantom 3S, but with my Mavic Pro1, which turned out to be the saving grace without which my Phantom would have surely gone AWOL under mysterious circumstances.

The Mavic Pro1 flew that programmed mission out way beyond signal range as is permissible where I live, and it was only later when I replayed the footage that I saw that the Mavic Pro, flying at what I thought to be 150 feet AGL, was in actuality flying way lower, and ultimately wound up on a collision course with a palm tree, at which point obstacle avoidance kicked in, causing the drone to swivel round and head straight to the launch point. Turns out that Litchi under-estimates altitudes whenever the launch point lies at a lower elevation than the course to be flown, with an error margin that can reach as much as a whopping 50 feet.

So your idea of running preliminary test flights with your Phantom4 is a very wise precaution for sure, before you fly a "blind" drone along the same route.

Very helpful. That is exactly the type of thing I wanted to have someone tell me about who has actually done it. My drafted mission will be ascending some incredibly rugged mountain terrain near the max ceiling limit of 1640 feet and the degree of underestimation of elevation by Litchi is what has been my concern. I'm hoping the p4p will have the tech to deal with and pioneer the trail. The ultimate goal? My p3SE found some incredible Barrier Canyon style pictographs (at a distance) that I'm sure have never been seen by an European. I can't wait to photograph them! If they pan out being what I think they are we have already starting planning an on the ground mission to ascend on foot (too steep and rugged for the mules/horses) as well. But with winter knocking on our door we probably won't be able to do that until late spring early summer. Cheers! I'll keep you posted.

 

[Meta4]

I'm considering using a p4p with obstacle avoidance as a trail blazer to fly a technically difficult first part of a Litchi mission

If your Litchi mission is so close to obstacles that you want obstacle avoidance, it's too close.
Because GPS is not pinpoint accurate and the barometric altitude can also vary, the path for the drone can easily be +/- 10 feet of more horizontally and vertically.
You need to allow a comfortable safety margin around obstacles.
I find it helps to first set out the mission with a more-than-enough safety margin and then watch the playback before adjusting things.

 

[Meta4]

Turns out that Litchi under-estimates altitudes whenever the launch point lies at a lower elevation than the course to be flown, with an error margin that can reach as much as a whopping 50 feet.

That sounds more like a case of the operator not realising that all heights are relative to the launch point and not allowing for that in the mission design.

 

[Billie Nelson]

That sounds more like a case of the operator not realising that all heights are relative to the launch point and not allowing for that in the mission design.

This was an oversight that I initially suspected since I do get absent-minded now and then, but when I scrutinized the Litchi flight that I'd created in the Mission Hub, all altitudes settings were not with respect to the launch point but were specified as intended to be above the current waypoint as the drone traveled.

That particular mission was the first time I'd launched a Litchi auto flight sortie from an elevation that was lower than the mission waypoints to follow. Virtually all my previous flights took off from a launch point that was a good 100 feet higher than the waypoint sequence flown, and I noted that for those flights Litchi tended to fly the drone considerably higher than I had intended, whereby I incrementally lowered the altitude on successive flights to reach the 150 feet AGL that has become my standard height above terrain in this rural area.

From this experience, I concluded that Litchi's altitude error is predictable to the extent that the discrepancy is a function of the altitude at the launch point relative to the altitude of all waypoints located along the flight path. With this quirk in mind, I no longer launch exploratory flights any lower than 246 feet AGL, so as not to cut things too close.