On an earlier flight, I was caught in the fog during a hyperlapse, but I managed to get the drone home safely, so a couple of days ago, at what I believed to be an oportunity to come up through a layer of fog and film the sunset on the top of this layer, I decided to try if I could do it (and succeeded after ascending 100 meters).  All was carried out in Normal mode.

Still, I got a lot of strange messages that raised a few questions.

• As far up as 20 meters, I got a message that Downward was 3 meters or closer.
• I did of course get a message about poor visibility (which it definitely was).
• At 75 meter above ground, I could see a clearing, but had no response when holding the left stick up. A message also appeared: Obstacle sensing failed in current flight direction and aircraft is breaking.  Recenter control stick and move them again to regain control of aircraft (This message strangely enough is not inluded in the flight log).  No indication otherwise that obstacles was seen on the radar, and the obstacle sensor icon was white, but suddenly got red when I recentered the controller stick and pressed up again.  After reaching max altidude, the obstacle sensor icon got white again.
• When returning, I was manually flying above the fog with a clear view, but still got a message of Low visibility.
• When being approx. 65 m away from home, I pressed RTH.
• I was then coming down into the fog, and of course getting message about Low visibility again.
• Strangely enough, I also got the following message: Vision positioning accuracy poor.  Unable to return to takeoff point.  Still the drone was continuing returning in a correct manner.
• At 24 meters height, I got a Downward message saying 1.2m.
• The drone was barely moving downwards, so I decided to push the down stick and disregard the messages to make sure landing area is safe (because it was).  A succesful landing!
  

• Am I correct in assuming that the fog in a big degree mess up the downward sensors?
• What kind of situation will prevent the drone from moving even if no obstacles are registered (preventing me to continue upwards)?
• Could I have avoided many of these issues if I had used Sports mode rather than Normal mode?
• When returning home, why do I get Low visibility even if the visibility straight ahead is perfect? Is it due to the downward sensors?  (I know that you cannot deselect obstacle sensing when pressing RTH, as RTH will override this and reselect obstacle sensing.)
• I did not get any indication on the screen that I was close to any obstacles (until I actually am), but still the drone behaves like obstacles are registered.
  

The flight log is available at https://drive.google.com/file/d/ ... Oj/view?usp=sharing
This is a short screen recording of the issues:

This was the short end result (worth the problems to me):

Ive had some of these issues flying when the sunlight is low in the horizon particularly if there is any dirt or oils from my fingers on the sensors. Sunlight directly in the sensor will cause the drone to break sensing something in front. This also goes for downward sensors in fog as that makes them think you are near ground or something it can land on. Best rescores in these situations is go into sport mode and that disables the sensors.

Tonyvdb Posted at 3-3 06:04
Ive had some of these issues flying when the sunlight is low in the horizon particularly if there is any dirt or oils from my fingers on the sensors. Sunlight directly in the sensor will cause the drone to break sensing something in front. This also goes for downward sensors in fog as that makes them think you are near ground or something it can land on. Best rescores in these situations is go into sport mode and that disables the sensors.

Best rescores in these situations is go into sport mode and that disables the sensors.
Sport Mode won't disable the downward sensors.
It would be better to disable Obstacle Avoidance and VPS sensors in the app settings.

Labroides Posted at 3-3 07:05
Best rescores in these situations is go into sport mode and that disables the sensors.
Sport Mode won't disable the downward sensors.
It would be better to disable Obstacle Avoidance and VPS sensors in the app settings.

That is a good suggestion if I decide to do this another time (even if I try to avoid it).  That day was just a too good possibility to get a good shot, but I have seen from the last time that the sensors (and the drone) may get covered in small drops of water, and I guess that will confuse the sensors.

At the ground this day it was -2 Celsius, but being higher before I returned home, I knew that the temperature higher up had been + 4-5 Celsius, so I hoped avoiding ice on the propellers.  I know that I should avoid such weather without having an IP classified drone, but I just had to take that chance.

I still wonder about the message on the screen saying I had to re-center the controller sticks to be able to continue up, because they were not apparent in the flight log (I found it really strange). Could it have been ice, or could it just be the sensors messing with me?

Tonyvdb Posted at 3-3 06:04
Ive had some of these issues flying when the sunlight is low in the horizon particularly if there is any dirt or oils from my fingers on the sensors. Sunlight directly in the sensor will cause the drone to break sensing something in front. This also goes for downward sensors in fog as that makes them think you are near ground or something it can land on. Best rescores in these situations is go into sport mode and that disables the sensors.

I know about the sun as I have encountered it on both my Mini 4 Pro and my Air 3S, so I always make sure to clean the sensors before flyg as a security mesure.

• As far up as 20 meters, I got a message that Downward was 3 meters or closer.
  [ downward sensor senses the fog, so no accurate height drone<>surface below ]
• At 75 meter above ground, I could see a clearing, but had no response when holding the left stick up. A message also appeared: Obstacle sensing failed in current flight direction and aircraft is breaking.  Recenter control stick and move them again to regain control of aircraft (This message strangely enough is not inluded in the flight log).  No indication otherwise that obstacles was seen on the radar, and the obstacle sensor icon was white, but suddenly got red when I recentered the controller stick and pressed up again.  After reaching max altidude, the obstacle sensor icon got white again.
  [ when craft is stopped bc of OA sensing obstacle (true or false), flying again needs all stick to center first, after that RC input works again ]
  

• When returning, I was manually flying above the fog with a clear view, but still got a message of Low visibility.
  [ flying close above the fog i think, so message Low visibilty is there, mayby our eyes does not see that low vis but apparantly the sensor does ]
• Strangely enough, I also got the following message: Vision positioning accuracy poor.  Unable to return to takeoff point.  Still the drone was continuing returning in a correct manner.
  [ not that strange, not all messages are in the log, as the log is decrypted by third part software and not all is found in the original data ]
• At 24 meters height, I got a Downward message saying 1.2m.
  [ yep, downward sensor 'measures' again the fog, IR height low will reduce donwward speed (as in a normal landing or flying from height to low height ]
• The drone was barely moving downwards, so I decided to push the down stick and disregard the messages to make sure landing area is safe (because it was).  A succesful landing!
  [ low IR height reducing downward speed ]
  

• Am I correct in assuming that the fog in a big degree mess up the downward sensors?
  [ yes, but i do not name it a big mess... ]
• What kind of situation will prevent the drone from moving even if no obstacles are registered (preventing me to continue upwards)?
  [ Disable OA sensors in the app, or select sport mode, but downward sensor is not de-activated ]
• Could I have avoided many of these issues if I had used Sports mode rather than Normal mode?
  [ as above ]
• When returning home, why do I get Low visibility even if the visibility straight ahead is perfect? Is it due to the downward sensors?  (I know that you cannot deselect obstacle sensing when pressing RTH, as RTH will override this and reselect obstacle sensing.)
  [ check the OA icon in the video, see it colors red completely ot partly, flying close above the fog so downward sensor is the "bad" sensor sometimes
  

In the fly app you can select the vision and landing protection OFF, this will prevent when full stick down + IR height = 0.5 meter going into a forced landing mode. Nice for flying in the fog....
BUT craft will fly full speed down into the ground as landing protection is off if you not stop the vertical down speed on time
How do i know....well did a test on this,  just a bit too late  ;-(


cheers
JJB

JJB* Posted at 3-3 12:32

As far up as 20 meters, I got a message that Downward was 3 meters or closer.
[ downward sensor senses the fog, so no accurate height dronesurface below ]

At 75 meter above ground, I could see a clearing, but had no response when holding the left stick up. A message also appeared: Obstacle sensing failed in current flight direction and aircraft is breaking.  Recenter control stick and move them again to regain control of aircraft (This message strangely enough is not inluded in the flight log).  No indication otherwise that obstacles was seen on the radar, and the obstacle sensor icon was white, but suddenly got red when I recentered the controller stick and pressed up again.  After reaching max altidude, the obstacle sensor icon got white again.

Hi JJB,

Thank you for well founded answers.  I must admit that I will keep the landing protection on, because I may forget that I turned it off and then (as you say) the landing speed will be much higher than I would like.  I am very confortable with that feature, because it allows me to fly in Normal mode and still be able to easily force land it in my hand or other suitable places (where the drone might not find it suitable), and it goes down sooo nice and slow (and I also tested that I can abort the landing using the Pause button - anything else will according to my experience not stop the landing.

In any case, I will not seek out to fly in the fog, but especially in the mountain, the fog comes easily sooner that you would expect, so nice to be prepared,

Cheers
Finn

fgange57 Posted at 3-3 12:14
That is a good suggestion if I decide to do this another time (even if I try to avoid it).  That day was just a too good possibility to get a good shot, but I have seen from the last time that the sensors (and the drone) may get covered in small drops of water, and I guess that will confuse the sensors.

At the ground this day it was -2 Celsius, but being higher before I returned home, I knew that the temperature higher up had been + 4-5 Celsius, so I hoped avoiding ice on the propellers.  I know that I should avoid such weather without having an IP classified drone, but I just had to take that chance.

I still wonder about the message on the screen saying I had to re-center the controller sticks to be able to continue up, because they were not apparent in the flight log (I found it really strange). Could it have been ice, or could it just be the sensors messing with me?
It's just DJI's poorly worded message to indicate that Obstacle Avoidance was braking to avoid a perceived obstacle.
If there is no real obstacle, you can ignore it.

Labroides Posted at 3-3 16:52
I still wonder about the message on the screen saying I had to re-center the controller sticks to be able to continue up, because they were not apparent in the flight log (I found it really strange). Could it have been ice, or could it just be the sensors messing with me?
It's just DJI's poorly worded message to indicate that Obstacle Avoidance was braking to avoid a perceived obstacle.
If there is no real obstacle, you can ignore it.

I have encountered several situations with a lot of obstacles met, but have never seen that message before (or experienced that I had to re-center the controller stick before continue moving.  Do you know of other situations where this may happen?

I wondered what would happen if I pressed "Landing" in the app, how would it determine the altitude?

Drone.Hunter Posted at 3-4 00:38
I wondered what would happen if I pressed "Landing" in the app, how would it determine the altitude?

I have experienced similar "landing" issues before, especially once where I without knowing it was hovering above some high power lines (I could see my drone, but due to the light, I did not see the upper ones, and they looked to be away from the drone looking at them in a distance).  I was going down, and then, I suddenly saw/heard a message that the drone was landing.  I managed to abort the landing, but I have several times used this way to force land in my hand (flying in Normal mode).  hat happen then is that the drone will start to descend very slowly, and whenever it feels like the downward movement stops, the propellers will also stop.

Watch from 2:15 in this video to the the "landing" on the high power line.

fgange57 Posted at 3-4 00:29
I have encountered several situations with a lot of obstacles met, but have never seen that message before (or experienced that I had to re-center the controller stick before continue moving.  Do you know of other situations where this may happen?

I've seen that message in flight logs many times.
You don't have to re-centre your sticks at all.
Like I said, the message is badly worded and only signifies that OA has acted to slow/stop your drone.

Drone.Hunter Posted at 3-4 00:38
I wondered what would happen if I pressed "Landing" in the app, how would it determine the altitude?

Your drone can only determine altitude if the ground or another surface is within the limited range of the VPS sensors.

At least the result was superb

Labroides Posted at 3-4 03:35
Your drone can only determine altitude if the ground or another surface is within the limited range of the VPS sensors.

What happens if you turn off the lower sensors and enable forced landing in FLY (without using sticks)?
In this case, I would implement turning on the sensors and landing in the normal mode. But in fact, how will it descend until it crashes?

Drone.Hunter Posted at 3-4 10:23
What happens if you turn off the lower sensors and enable forced landing in FLY (without using sticks)?
In this case, I would implement turning on the sensors and landing in the normal mode. But in fact, how will it descend until it crashes?

Do you realise that you can land the drone yourself ?

Labroides Posted at 3-4 12:51
Do you realise that you can land the drone yourself ?

I know.
I mean the automation. The pilot forgot that he had turned off the sensors. He flew to the home point and pressed the landing button.The obstacle sensors can be disabled for manual control. But they always turn on when the automatic mode is turned on. This is the behavior I would expect from the lower sensors.

Labroides Posted at 3-4 03:33
I've seen that message in flight logs many times.
You don't have to re-centre your sticks at all.
Like I said, the message is badly worded and only signifies that OA has acted to slow/stop your drone.

It may absolutely be possible that you didn't have to re-centre the sticks, but in my case, the drone totally stopped moved forwards and did not continue to move before I did what the message suggested to do (re-centre and push up again).

Montfrooij Posted at 3-4 09:47
At least the result was superb

Thank you, and I am very satisfied, as this is a scenario that I have been thinking of ever since I got a drone, but this is the only day where the fog layer was thin enough at an exactly right time

fgange57 Posted at 3-5 01:54
Thank you, and I am very satisfied, as this is a scenario that I have been thinking of ever since I got a drone, but this is the only day where the fog layer was thin enough at an exactly right time

Yeah, that is always hard to predict. I tried many times and only got the right layer 3 times.

fgange57 Posted at 3-5 01:54
Thank you, and I am very satisfied, as this is a scenario that I have been thinking of ever since I got a drone, but this is the only day where the fog layer was thin enough at an exactly right time

This was my lucky day

Labroides Posted at 3-4 03:35
Your drone can only determine altitude if the ground or another surface is within the limited range of the VPS sensors.

If you look at the end of my video, what the down sensor measure as distance to ground is irrelevant when the landing sequence is initiated.  At 15-20 meters above ground, the down sensors reported 1,2 meters above ground, but when I pressed the down stick, the landing commenced slowly until the drone landed.

Montfrooij Posted at 3-5 01:58
Yeah, that is always hard to predict. I tried many times and only got the right layer 3 times.

I was lucky this day, as coming beck from a trip and moving down back, I could see that the fog layer possibly was not too high, but normally very difficult to get is perfectly right.

Montfrooij Posted at 3-5 02:00
This was my lucky day

https://www.youtube.com/watch?v=ViVJYgufjek

I really like to see the church spire popping up from the fog, and getting a light like this make the mood magical.

Drone.Hunter Posted at 3-4 10:23
What happens if you turn off the lower sensors and enable forced landing in FLY (without using sticks)?
In this case, I would implement turning on the sensors and landing in the normal mode. But in fact, how will it descend until it crashes?

Interesting question, and in fact may interesting questions regarding what is possible or not with the sensors on or off and results in different scenarios.  This is something I really want to test (but I will use my Mini 4 Pro, as the impact when coming down is less harsh due to the low weight.

What I have seen though is that when RTH is selected, it seems to turn on sensors at least when in Sports mode.  It will definitely be interesting to test more to know what to expect.

fgange57 Posted at 3-5 02:06
I was lucky this day, as coming beck from a trip and moving down back, I could see that the fog layer possibly was not too high, but normally very difficult to get is perfectly right.

Yeah, that makes it more easy (and still requires a lot of luck)

fgange57 Posted at 3-5 02:07
I really like to see the church spire popping up from the fog, and getting a light like this make the mood magical.

I could not see how thick it was when I left with the drone, but I decided to take my chance because I suspected it would be gone soon. (which turned out to be true)
But this gave a short 'perfect' window.

Montfrooij Posted at 3-5 02:15
Yeah, that makes it more easy (and still requires a lot of luck)

I agree, because I actually expected that the fog layer would be lower, and the fog may move very fast.
Here is my first short encounter:


And a short test next time it was fog (to be prepared)

Montfrooij Posted at 3-5 02:15
I could not see how thick it was when I left with the drone, but I decided to take my chance because I suspected it would be gone soon. (which turned out to be true)
But this gave a short 'perfect' window.

Yes, that is the scare moment.  This is why I did a test to see what to expect in the fog (as you can see in my previous post).

fgange57 Posted at 3-5 02:21
I agree, because I actually expected that the fog layer would be lower, and the fog may move very fast.
Here is my first short encounter:
https://youtu.be/XSE6kDb2pvw

Very interesting to see.
My Mini 3 Pro is not that advanced, but it is equally scary.

fgange57 Posted at 3-5 02:22
Yes, that is the scare moment.  This is why I did a test to see what to expect in the fog (as you can see in my previous post).

Yeah, fog and drones are a dangerous combo.

Montfrooij Posted at 3-5 02:30
Yeah, fog and drones are a dangerous combo.

During the test I did, the drone was actually covered in small water drops, so the flights I have done is the exception.  I try to avoid fog.

fgange57 Posted at 3-5 02:46
During the test I did, the drone was actually covered in small water drops, so the flights I have done is the exception.  I try to avoid fog.

Yeah, same here.

Drone.Hunter Posted at 3-4 18:05
I know.
I mean the automation. The pilot forgot that he had turned off the sensors. He flew to the home point and pressed the landing button.The obstacle sensors can be disabled for manual control. But they always turn on when the automatic mode is turned on. This is the behavior I would expect from the lower sensors.

Hi,

Checked, when, with all the sesnsor OFF (advanced settings) , RTH or autolanding is selected all sensors are ON again. The moment the RTH or landing is cancelled the all sensors are OFF again.

At end of video you see how easy it is to 'crash' into the ground...



cheers
JJB

fgange57 Posted at 3-5 02:13
Interesting question, and in fact may interesting questions regarding what is possible or not with the sensors on or off and results in different scenarios.  This is something I really want to test (but I will use my Mini 4 Pro, as the impact when coming down is less harsh due to the low weight.

What I have seen though is that when RTH is selected, it seems to turn on sensors at least when in Sports mode.  It will definitely be interesting to test more to know what to expect.

see post #34

JJB* Posted at 3-5 06:17
see post #34

And see my response in #35

JJB* Posted at 3-5 06:16
Hi,

Checked, when, with all the sesnsor OFF (advanced settings) , RTH or autolanding is selected all sensors are ON again. The moment the RTH or landing is cancelled the all sensors are OFF again.

Thank you for testing, very good results. Now you can be calm.

Drone.Hunter Posted at 3-5 07:57
Thank you for testing, very good results. Now you can be calm.

lol   i am always calm....

JJB* Posted at 3-5 10:53
lol   i am always calm....

Pilot is calm

fgange57 Posted at 3-5 02:46
During the test I did, the drone was actually covered in small water drops, so the flights I have done is the exception.  I try to avoid fog.

Sensors do not like moisture. Especially LASERs. Each tiny molecule refracts the beam. Looks really good in movies, though lol