VPS Landing issue - intermittent and incorrect clearance value

[hainerob]

Hi Guys,

Purchased a Mavic Pro about 2 weeks ago, and I've been flying it in a big open grassy field since then to make sure that I am very familiar with its operation, safe control and flight modes before I focus too much on taking great photos and video with it.

I have had a strange thing occur to me several times now that I had previously put down to pilot error, but I'm beginning to think is a fault.

Sometimes when I take off using the DJI go app auto takeoff feature, The drone will take off, and raise beyond the 1.5 meters, and keep going and going. VPS or Clearance on the controller will display an incorrect figure like 0.5m. Because the drone keeps rising, instinct is to pull the left stick down, which then begins the drone "Landing" which, from 15m or so, takes a very long time.

At one stage, the drone was in the air at around 50m or so, I pulled the stick down to descend, it appeared to not respond, and then started "Landing", and coming down very, very slowly.

Also, at one point when I was trying to land, the drone was physically 0.5m from the ground, but read 4.5m, and as a result of this, would not properly land. --- I ended up flying it higher and catching it.

This seems to be intermittent, and is more likely to happen in the first flight in a session.
I've had it happen to me on two days now, both days were nice sunny days, with light to medium winds if that has any bearing.

I would think if this was a calibration issue, it would be more consistent. VPS seems to work properly most flights.

I'm about to start looking for logs from today.

Ideas? Do I have a faulty Mavic here?

 

[Chris_GREECE]

grassy field

Have you try to take off from non grassy field?
When you say grassy may i ask you if during take off procedure the visual sensor is covered by the grass?

 

[hainerob]

grassy field

Have you try to take off from non grassy field?
When you say grassy may i ask you if during take off procedure the visual sensor is covered by the grass?

Hi Chris_GREECE,

I actually had taken off from a park table in the field (a very big park), as the props of the mavic don't clear the grass. I generally try to take off and land on a hard surface. I have had the same issue taking off on gravel, and from a large rock.

No, the visual or ultrasonic sensors are clear at all times.

 

[Chris_GREECE]

OK, then as you say take a look at the logs, maybe it is written there what is going wrong.

 

[hainerob]

OK, then as you say take a look at the logs, maybe it is written there what is going wrong.

What I can see in the logs so far, is a GPS Height of 106m and a VPS height of 0.2 and "ForcedLanding" taking place. I thought I was much lower when that first happened. Clearly I was wrong....

Still going through the logs, wow... they are big!

 

[msinger]

@hainerob, those things happen when the downward sensors incorrectly detect the ground is near. When that happens mid-flight, you can disable the Landing Protection setting to prevent the auto descent/landing. You'll find that setting in the following section of DJI GO:




Here are the usual cases where the downward sensors incorrectly detect the ground is near:

• Something is dangling beneath the Mavic (e.g. a GPS tracker antenna)
• A 3rd party accessory is installed beneath the Mavic (e.g. extended landing gear)
  
• The sensors needs to be calibrated like this
• The sensors are dirty and need to be cleaned
• The sensors are damaged and need to be replaced (not a common problem)

 

[hainerob]

Hi msinger!

@hainerob, those things happen when the downward sensors incorrectly detect the ground is near. When that happens mid-flight, you can disable the Landing Protection setting to prevent the auto descent/landing.

Yes, I'm aware of this setting, with every intent of using this in an emergency, but I would expect that the sensors would be more reliable than this?

Here are the usual cases where the downward sensors incorrectly detect the ground is near:

• Something is dangling beneath the Mavic (e.g. a GPS tracker antenna)
• A 3rd party accessory is installed beneath the Mavic (e.g. extended landing gear)
  
• The sensors needs to be calibrated like this
• The sensors are dirty and need to be cleaned
• The sensors are damaged and need to be replaced (not a common problem)

None of the above conditions mentioned above apply to my Mavic. It exists in as new condition, without modification. I will try to calibrate the sensors but my understanding is that the VPS is calculated using the ultrasonic sensors, for which, unless I am mistaken, there is no calibration process. I am of the understanding that the downward facing cameras are used for the precision landing terrain identification, and for flying indoors in the absence of GPS coverage - (I haven't gotten to testing these features just yet)

Here is an extract from the log showing the inconsistencies in the sensors. During this flight, VPS never worked correctly:

OSD.flyTime, OSD.sWaveHeight, OSD.height, OSD.flycState
0.2, 0.2, 0, EngineStart
0.3, 0.2, 0, EngineStart
0.4, 0.2, 0, EngineStart
…, , ,
1.4, 0.2, 0, AutoTakeoff
1.5, 0.2, 0, AutoTakeoff
1.6, 0.2, 0, AutoTakeoff
…, , ,
7.1, 0.2, 2.2, GPS_Atti
7.2, 0.2, 2.2, GPS_Atti
7.3, 0.2, 2.1, GPS_Atti
…, , ,
11.4, 0.1, 3.3, GPS_Atti
11.5, 0.2, 3.3, GPS_Atti
11.6, 0.2, 3.3, GPS_Atti
…, , ,
24, 0.2, 7.8, GPS_Atti
24.1, 0.2, 7.9, GPS_Atti
24.2, 0.2, 8, ForceLanding
24.3, 0.2, 8.1, ForceLanding
…, , ,
46.6, 0.2, 5.2, ForceLanding
46.7, 0.2, 5.2, ForceLanding
46.8, 0.2, 5.1, ForceLanding
…, , ,

 

[msinger]

Here is an extract from the log showing the inconsistencies in the sensors. During this flight, VPS never worked correctly

Please upload your TXT flight log here and post a link back here. You'll find instructions for locating your TXT flight log at that link.

 

[hainerob]

Please upload your TXT flight log here and post a link back here. You'll find instructions for locating your TXT flight log at that link.

Whilst I'm very happy to provide relevant information out of my log files, I'd prefer not to upload them in their entirety to a website or public forum.

You've pretty much confirmed what I believed anyway, so I'm going to contact DJI support and see what they have to say.

Thanks for your help!

 

[rickw]

just a shot in the dark,did you remove clear protective covers from sensors?

 

[f3honda4me]

Hi msinger!



Yes, I'm aware of this setting, with every intent of using this in an emergency, but I would expect that the sensors would be more reliable than this?


None of the above conditions mentioned above apply to my Mavic. It exists in as new condition, without modification. I will try to calibrate the sensors but my understanding is that the VPS is calculated using the ultrasonic sensors, for which, unless I am mistaken, there is no calibration process. I am of the understanding that the downward facing cameras are used for the precision landing terrain identification, and for flying indoors in the absence of GPS coverage - (I haven't gotten to testing these features just yet)

Here is an extract from the log showing the inconsistencies in the sensors. During this flight, VPS never worked correctly:

OSD.flyTime, OSD.sWaveHeight, OSD.height, OSD.flycState
0.2, 0.2, 0, EngineStart
0.3, 0.2, 0, EngineStart
0.4, 0.2, 0, EngineStart
…, , ,
1.4, 0.2, 0, AutoTakeoff
1.5, 0.2, 0, AutoTakeoff
1.6, 0.2, 0, AutoTakeoff
…, , ,
7.1, 0.2, 2.2, GPS_Atti
7.2, 0.2, 2.2, GPS_Atti
7.3, 0.2, 2.1, GPS_Atti
…, , ,
11.4, 0.1, 3.3, GPS_Atti
11.5, 0.2, 3.3, GPS_Atti
11.6, 0.2, 3.3, GPS_Atti
…, , ,
24, 0.2, 7.8, GPS_Atti
24.1, 0.2, 7.9, GPS_Atti
24.2, 0.2, 8, ForceLanding
24.3, 0.2, 8.1, ForceLanding
…, , ,
46.6, 0.2, 5.2, ForceLanding
46.7, 0.2, 5.2, ForceLanding
46.8, 0.2, 5.1, ForceLanding
…, , ,

The sensors can be damaged by debris, or impeded by dust/debris.