What's the bottom line here?

[JLane]

Ok. I turned off VPS and Landing Assist. I flew this mission completely by hand.... I noticed a few discrepancies in the altitude readings however. I flew the drone up to an iceberg at about 5-10feet above the water (all sensors were off)... the depth on my controller read -3 feet. I saw this happen more than once where my altitude was actually a "negative" number. I didn't stay that low for long and I'm glad I powered off my sensors.

Just so you know, those negative numbers come from the baro/GPS sensors, and it's fairly common for that reading to vary a bit and sometimes go negative. It happens over dry land, as well. That's why the VPS system takes over when it's low enough, because the cameras and sonar sensors can read the height off solid ground more accurately than the baro/GPS sensors. The VPS height reading over ground is often different from the baro/GPS reading, and is usually more accurate.

 

[Babur]

hi everyone..

i do not exactly know if question fits the topic of this thread but it sure is related, especially after aringhof's experience:

i am about to try a flight route off a high cliff. my bird will first take off from the cliff, fly high and then down down down. most of the flight root will be below the take off altitude/height..

all of my (quite limited) flight experience is at the beach so this will be rather complicated for me.

will my mavic mix up nominal/relative altitude/height? would that trigger unwanted auto-action that would jeopardise everything?
should the landing protection be off?
what else?
and by the way would all be the same if the take off point is a high rise building? (a hill/cliff might be properly recorded on the map data but a building might not be there..)

i need help. your comments most appreciated.

 

[dewster]

The manual says that flying over monochromatic surfaces such as snow or water will cause VPS errors. There's a video somewhere on YouTube that show a Mavic darting off at high speed when the pilot was trying to take a selfie.

I turned VPS off yesterday while flying over water. You'll just have to focus more but the Mavic held position. It also flew a little faster.

You can turn it on and off in flight, but it may be better if you plan ahead while on the ground.

Just remember that with the bottom sensors turn off there's no landing protection so watch the speed of your descent during landing. It will not slow.

 

[Babur]

thank you. my question was regardless of the surface flown over.

is mavic software/hardware ready to handle flight with 'landing protection on' below its take off altitude?

 

[Babur]

would rth work? would mavic fly back up home if signal lost?

 

[Flawless]

The Mavic is perfectly capable of descending below its RTH point. If you set RTH height to 30m, it will ascend to 30m above the altitude it took off from.

If you're currently flying off a cliff, 50m below where your Mavic took off from, it will ascend 80m during RTH.

 

[Babur]

Thank you Flawless!

And will it try to initiate landing if below take off point? Do I have to shut any options down for that? Landing protection?

 

[aringhof]

i find myself just flying manually all the time now. i use the realtime video screen to see what's in front and below me. these sensors seem logical in theory but there are too many unforeseen variables that could cause a crash.

 

[Babur]

Thank you!!

 

[maccardiolog]

While I totally agree that the naming of "Landing Protection" is terrible, it's not simply the VPS as you have stated. Landing Protection is a completely separate option available in the Advanced settings of the Vision Settings.

Now, aside from whatever strange descriptions DJI might give it in the manual or app, here's a brief overview of why it's important and especially relevant when flying over water:

1. Landing Protection basically prevents you from flying the Mavic closer than 0.5m above the ground/objects below. With LP enabled (the default setup), the Mavic will automatically rise if it detects anything closer than 0.5m below it. With LP disabled, you can fly your Mavic as close as you want to the ground/objects and it won't try to ascend.

2. With LP enabled, a side-effect is the ability to initiate a forced auto-landing by holding the left stick down when the Mavic is at or below 0.5m. This is handy when you're doing it intentionally, but not so great if the VPS system is falsely reading the Mavic's height at less than 0.5m and initiates an auto-landing over water when you don't expect it.

3. In the two most recent versions of the firmware (.0500 and .0550), this forced auto-landing can't be aborted by using the throttle or the Pause button. The only way to abort this landing is by flicking the Sport mode switch.

Hello JLane and thank you very much for clarification in such a professional manner . I ask you :
1. if the LP - on or off - will affect the RTH (any of the three modalities , smart, low battery , failsafe )
2.if there is an interrelation between LP and Precision Landing (PL) ? Would the result be different with different settings , eg what if the LP will be set on and PL off or viceversa ? What will be the results in RTH and manually return to home situations ?
Excuse me if my questions are off topic , but were a lot of the discussions about LP and the subject is very important .

 

[Flawless]

Hello JLane and thank you very much for clarification in such a professional manner . I ask you :
1. if the LP - on or off - will affect the RTH (any of the three modalities , smart, low battery , failsafe )
2.if there is an interrelation between LP and Precision Landing (PL) ? Would the result be different with different settings , eg what if the LP will be set on and PL off or viceversa ? What will be the results in RTH and manually return to home situations ?
Excuse me if my questions are off topic , but were a lot of the discussions about LP and the subject is very important .

LP won't affect RTH at all.

The LP and PL functions operate independently. PL records the takeoff and reverses that for landing. LP tries to prevent your Mavic slamming into the ground and damaging the gimbal (since there's less ground clearance than, say, a Phantom).

You can disable LP and still use Precision Landing, and vice versa.

 

[maccardiolog]

Thank you Flawless ! Need the height be the SAME (approx 10 m ) in both modalities (auto and manually takeoff ) ? How would be the Mavic behaviour in RTH with LP on and PL off ? Without same precision as in PL on situation ? I suppose the settings were made before flying , not during it .

 

[JLane]

Thank you Flawless ! Need the height be the SAME (approx 10 m ) in both modalities (auto and manually takeoff ) ? How would be the Mavic behaviour in RTH with LP on and PL off ? Without same precision as in PL on situation ? I suppose the settings were made before flying , not during it .

Landing Protection has no reall effect on RTH or Precision Landings. Do everything as normal for making Precision Landing work.

There is just one slight difference in the landing during RTH, because with Landing Protection off, the Mavic doesn't seem to pause near the ground and wait for you to confirm the landing area. It will just land.

You can enable/disable Landing Protection during flight.

 

[JLane]

thank you. my question was regardless of the surface flown over.

is mavic software/hardware ready to handle flight with 'landing protection on' below its take off altitude?

Landing Protection does not use the GPS or barometric altitude readings to determine if it's close to the ground. It uses the VPS sensors (mainly the ultrasonics). A negative relative altitude based on GPS and baro readings will never cause Landing Protection or Forced Auto Landing to kick in. They only activate when the ultrasonics detect something less than 0.5m away.

 

[maccardiolog]

Excuse me for delayed thanks , JLane !

 

[dmyers7]

Keep your batteries warm. Cold lipo batteries deliver less energy which can cause a premature landing and hopefully your not over water at the time. Many pilots keep them on an inside coat pocket until you need them for flight. Remember your mobile device and controller will be exposed to the elements so a USB mobile charging pack plugged into the bottom port of the controller can help keep that happy for extended periods. iOS devices won't charge from this setup, but they seem to be ok with minimized discharging plugged into the controller. All this has worked well on below freezing days for me.