precision landing protocol question

[MavicFrank]

+1. Although I try to take off and land in wide open spaces, this is bothersome. I would recommend calibrating the snot out of everything, including the controller.

 

[Logger]

In the past few days my Mavic has developed a habit of flying away laterally, mid way through a precision landing. Done it twice now in different flight locations. Precision Landing all looks to be going perfectly, with "rectifying aircraft position messages" verifying the system has the required info to complete the task. Landing target is vertically right beneath aircraft an I can see it in cross hairs and in video. Gets down to ~ 2 metres or 6' and then heads off laterally at about 5kmh while continuing the descent toward the ground. Popping up a ground safe to land message as it is about to autoland onto the ground at 5kmh. No thankyou. At this point it is about 30 feet from home point, that it had previously been right over and I cancel it and fly back manually.

View attachment 7754

in this graph you can see how speed and distance to home point are essentially 0 from ~77 to 92 as it descends vertically and precision landing kicks in about 83 when the vpsHeight comes in. At 92 and 2.1 m it heads for the hills for no apparent reason.

I have checked the logs and can see no stick input. This ties in with me being hands off. I thought maybe the controller might have got interference and booted in an input. But nothing there. The front sensors are not seeing anything so no obstacle. . This happened to me once before a couple of days ago too. Both events occurred since the new firmware and DJIGo android 4.0.4. Further since this update it is fussy about precision landing and often reports Area not suitable for landing at a spot it has happily precision landed on for the past 4 months. So there appear to have been some software changes to the process.

I operate with precision landing On, but landing protection OFF so it does not stall the landing if the ground is not flat.

Any suggestions as what might cause this cause? I am wondering it the recent tweaks to precision landing may have introduced a bug.

Starting to wonder if this issue (which has occurred twice to me since the mew firmware) may be related to the Erratic Flight behaviour that third party developers are reporting. I was using DJIgo4 at the time , but in a sense Precision Landing is a sub-mode of Auto-land, vaguely analogous to Litchi and Autopilot modes submodes of P Mode. It sure had Erratic flight behaviour!

Another possibility is there was a dirty big metal water pipe buried beneath the landing site. But if this was the case I should have got interference messages. The subsequent 5 or so attempts to recreate the flight at the same spot would have failed too. But they all worked fine. Odd.

 

[dewster]

DJI should chill out on the firmware updates.

 

[MacPhersonCa1]

Home point is recorded upon take off, and cannot not be refreshed during flight.

Actually you can update your home point during flight based off of RC position or your AC position.

 

[msinger]

Actually you can update your home point during flight based off of RC position or your AC position.

True. But, you shouldn't do that if you want to use the precision landing feature (which is what we're discussing in this thread).

 

[MacPhersonCa1]

True. But, you shouldn't do that if you want to use the precision landing feature (which is what we're discussing in this thread).

You are correct. I should have realized.

 

[THOMASHUNTLEY]

Hi,
I would just like to add my tuppenceworth to this , i recently bought a MAVIC PRO , have flown it approx 5/6 times , and have just used the take off button on the app , it gives you the option to use precision landing and when it takes off it climbs to approx 10 mtrs , you can then just fly off and do your thing , if you decide to do a RTH , it comes back to the EXACT spot it took off from ,EVERY TIME!!
I for one think it is brilliant.

 

[MacPhersonCa1]

Hi,
I would just like to add my tuppenceworth to this , i recently bought a MAVIC PRO , have flown it approx 5/6 times , and have just used the take off button on the app , it gives you the option to use precision landing and when it takes off it climbs to approx 10 mtrs , you can then just fly off and do your thing , if you decide to do a RTH , it comes back to the EXACT spot it took off from ,EVERY TIME!!
I for one think it is brilliant.

Yes, it is.

 

[utsavchopra]

You cannot do precision landing in an indoor environment. I think you need to build an additional solution for that or get it from someone who are already doing this.

 

[Shakennstirred]

Yes it's very accurate, I tested it a few weeks ago and it landed with in an inch of where it took off from

 

[Steady Eddie]

Hi,
I would just like to add my tuppenceworth to this , i recently bought a MAVIC PRO , have flown it approx 5/6 times , and have just used the take off button on the app , it gives you the option to use precision landing and when it takes off it climbs to approx 10 mtrs , you can then just fly off and do your thing , if you decide to do a RTH , it comes back to the EXACT spot it took off from ,EVERY TIME!!
I for one think it is brilliant.

I think your observations are spot on. I'd like to know what you term "EXACT" though. My experience when using precision landing, ie. checking the box before moving the slider across to take off, is that it will land within a radius of about 25 cm (10 in) or so from it's take off spot most of the time. Often it's further off than that though.

I also think that wind has an effect on the absolute precision.

Even a very light breeze at take off will shift the drone, and confuse the two small downward facing cameras when determining the home spot as it rises to 10 m or so. "Aircraft must take of vertically" in the manual is the key here I think.

It seems the GPS fix is determined before takeoff, as indicated by the slow flashing green status indicator. Not necessarily accurate to within centimeters though. Maybe the longer you wait before takeoff, the more averaging the software will do to achieve the best possible GPS fix.

Only those clever Chinese engineers would know all the answers I guess. Us mortals are left to speculate.

 

[Dragonfly]

To clear up precision landing.
There are 2 types of RTH.
One is the drone Records the Home point GPS location (this is announced as recorded) you then take of and fly away.
When you hit RTH the drone will return to the GPS location but may be off by 2 or 3 feet or more as that is just the inaccuratcy off the GPS. 2 outa 6 times it may be spot on, just luck. 4 outa 6 close.

The second is as per the first but you raise the drone straight up for at least 10 meters plus then fly off.
What now is going on is the bottom two cameras are taking a series of MONO pictures of the take of point and temporarily storing them.
When you now hit RTH the drone will arrive above landing area and start to descend but will be off by two or even four feet but as its decending, it will now use the Mono pictures stored and match to the camera visual it now sees and move its position and align its itself over the exact take off point as it descends.

For this to be effective, lighting must be correct (not to bright or too dark) the ground or take off point must have different contrast (no one colour or pattern) and should not change from when drone took off to when drone returns to land.

The purpose of requirement of 10 plus meters above take off is for the camera to take a large enough mono pic to match the scene so on return to locate the landing point.
Drone should raise directly above takeoff point. (note, if slight to strong breeze / wind then drone can shift 8 to 12 inches or more as it accends so takeoff point will shift that distance as per mono pics causing landing point to now be out by that 8 to 12 inches.)

When done successfully you can watch your drone that can be 3 meters out off landing point move across as its descending and matching the pic with pinpoint accuracy to Finnaly touch down right on target.

 

[donl1924]

A used real estate or political sign makes a great landing pad