Dynamic Home Point Control Logic, Mavic 4 Pro

[MS Coast]

I just flew about a dozen Dynamic Home Point operations and have a few observations and conclusions to share. And some questions. Comments, corrections, and additions are appreciated.

I used the RC 2 ( not the Pro) controller. In all cases, the drone was more than 75 yards from the home point. Any special behavior for cases where the drone is close to the home point (within 50 meters) wasn't tested. There were no landings between RTH operations except in one case for a battery change. The maximum elevation difference between the home points was less than about 15 feet.

Basic Operation

• Dynamic Home Point altitude is governed by the Static RTH return altitude setting.
  • If the drone is below that setting, it climbs vertically to reach it before proceeding.
  • If the drone is above that setting, it remains at it's current altitude.
• The drone then flies at constant altitude until it's very near the home point.
• If the RTH return altitude is above the Static RTH altitude setting, the drone descends to the Static RTH altitude over the home point.
• The drone hovers at the home point and waits for input or, presumably lands when the battery state of charge reaches some critical level.
• The pilot takes over and lands the drone.

This logic seems to make a lot of sense and should keep the drone safe as long as the pilot has the good sense not to use Dynamic Home Point and RTH indoors, deep in a thick forest, or while standing next to an television antenna mast and wait too late to assume control.

Observations and Quirks

• As noted in the manual, the home point symbols and control icon change color to blue.
• It appears that the accuracy of the home point location as set by the GPS in the controller isn't as good as the accuracy of the drone's GPS location. That may explain the "near the home point" language in the manual. It was still within 5 yards or so of the actual controller location.
• The return altitude was near constant (+/- one foot) until the drone neared the home point.
• If the return altitude was greater than the Static RTH altitude setting, the drone began descending before reaching the home point, (within 15 yards of so).
• After the drone has begun RTH return to the home point and before it enters hover mode, it will react to the controller location changing and proceed to the new home point.
• Once the drone enters hover mode, it does not respond to changes in the controller location.
• The drone leaves hover mode immediately after a control movement is made.

Questions

• Is the hover altitude adjusted for differences in the barometric altitude and sensor altitude, i.e. as might be caused by differences in terrain elevation?
• It appears that the hover altitude may be increased when the home point is near obstacles? Is that true? Are OA functions involved?
  In some cases when the controller was within about within about ten yards of 30-80 foot tall trees, the drone would either climb to a higher altitude than the Static RTH altitude or descend to an altitude higher than it. Differences above the Static RTH altitude of about 20 were noted.
• Or, is there another explanation for the increases in hover altitude?
• Are there any control logic changes when there is a substantial difference in the takeoff location and a home point set by Dynamic Home Point?
• What is the distance change in the controller location that triggers establishing a new home point?
• How does Dynamic Home Point alter the RTH control logic when RTH is initiated within 50 meters of the home point?

Next Flights

• Try to understand the hover altitude adjustments. Use Dynamic Home Point RTH in locations without trees or other obstacles that might trigger OA functions to adjust the hover altitude within 50 yards or so.
• Sort out the controller movement distance that triggers a new home point.

Other than the basic operation conclusions, I doubt that any of the rest will ever matter much to most of us. But it's fun to tinker with.

 

[GadgetGuy]

I also strongly suspect that the only answers to your questions will have to come from us, based upon your results and our limited crowd sourced user testing, as DJI is unlikely to have any correct answers, as they haven't yet documented how it should work, let alone how it is actually currently working. It's reviving an old feature in an entirely different environment with OA and Lidar and intelligent RTH capabilities. With so few Mavic 4 Pro's in the U.S.., it's going to be even more difficult than in the past to get crowd-sourced answers from DJI's largest user base.

The Mini 5 Pro also features Dynamic Home Point, which likely operates identically. However, I'm not sure if that is only when used with the RC Pro 2, like it is with the Mavic 4 Pro, or whether it might be possible when the Mini 5 Pro is flown with the RC-N3 with a smart phone for GPS.

Anyone know which controllers for the Mini 5 Pro support Dynamic Home Point?

One bright spot is we may see more Mini 5 Pro's being imported because the risk from tariffs is on a much lower price that is 25% of a Mavic 4 Pro, and many S. Korean sellers are guaranteeing no tariffs (perhaps because they are prepaying them?). That's how my order was placed.

Let's tinker away!

 

[BossBob]

As GPS is only accurate to 10 to 15 ft it will never be as accurate as the home point visually recorded by the downward facing camera on the drone. Given that you are using 2 gps devices at extreme you could have the drone landing 30ft away. Surely dynamic home point would be used to bring the drone to the area of the controller so the operator could then choose the place to land it.

 

[iceman77]

Surely dynamic home point would be used to bring the drone to the area of the controller so the operator could then choose the place to land it.

And that's exactly what I would intend to use this feature for. Have the drone come close, I take over and land manually. It would be another story, if, god forbid, you RC dies (for whatever reason). That off-the-boat launch situation here would be disastrous!

 

[MS Coast]

However, I'm not sure if that is only when used with the RC Pro 2, like it is with the Mavic 4 Pro, ...

Dynamic Home Point is available with the RC 2 controller and Mavic 4 Pro.