RTH Failsafe procedure and satellites numbers - Quick questions

[laurent45]

Hi MM2 pilots
I had my first flight today, and thanks to all your advices,.. it went fine.... but tI will keep practicing and updating my checklist.
I have 2 questions :
1- Minimum number of GPS satellites : When I checked on the UAV app, I had only 10 sats,.. and it was in RED status and because of this it was "No good to flight", but the DJI app saif it was OK to fly. So maybe the UAV app was not tuned correctly, that is why I would to know what is the minimum number of satellites required by the Mini2
2- During this first flight I lost the connection between the Mini2 and the controler a couple of times even I was at 500meters (in open air), and got it back a few seconds after each time. So I tried to test the smart RTH and it worked. Tonight I looked in user manual at the RTH Failsafe. AND a sentence is confusing me "The aircraft will fly backwards for 50 m on its original flight route and ascend to the preset RTH altitude to enter Straight Line RTH. The aircraft enters Straight Line RTH if the remote controller signal is restored during Failsafe RTH", but what is happening IF the signal is NOT restored ? Does-it continue to fly back to Homepoint ?

Thanks in advance to all

 

[Meta4]

1- Minimum number of GPS satellites : When I checked on the UAV app, I had only 10 sats,.. and it was in RED status and because of this it was "No good to flight", but the DJI app saif it was OK to fly.

The absolute minimum is 6 sats, but you will usually require more because there's more to it than a simple number.
The sats have to be well spread around the sky to provide good satellite geometry necessary for accurate location data.

So maybe the UAV app was not tuned correctly, that is why I would to know what is the minimum number of satellites required by the Mini2

There's no "tuning" or any configuring that would make any difference.
If your drone is out in the open with a clear, unobstructed skyview, you'll always have plenty of sats and no problems with GPS.
If you launch from a place where trees, buildings etc block large parts of teh sky, the drone will take longer to get good GPS data (or might not if too much of the sky is blocked).

Tonight I looked in user manual at the RTH Failsafe. AND a sentence is confusing me "The aircraft will fly backwards for 50 m on its original flight route and ascend to the preset RTH altitude to enter Straight Line RTH. The aircraft enters Straight Line RTH if the remote controller signal is restoredduring Failsafe RTH", but what is happening IF the signal is NOT restored ? Does-it continue to fly back to Homepoint ?

The wording in the manual is confusing and the actual meaning is not clear.
It's likely to be poorly written and/or a bad translation.

With previous DJI drones that could retrace their path after signal loss, the drone would cease flying backwards if signal was regained and the operator could resume flying normally.
If signal was not regained, then the drone would enter straight line RTH.

Having it work that way is probably the most sensible way for DJI to have programmed it.
I'd suggest a little testing in a large, open area to see what really happens.
Fly out >20 metres, switch off the controller and observe what the drone does.

 

[tlswift58]

Hi MM2 pilots
I had my first flight today, and thanks to all your advices,.. it went fine.... but tI will keep practicing and updating my checklist.
I have 2 questions :
1- Minimum number of GPS satellites : When I checked on the UAV app, I had only 10 sats,.. and it was in RED status and because of this it was "No good to flight", but the DJI app saif it was OK to fly. So maybe the UAV app was not tuned correctly, that is why I would to know what is the minimum number of satellites required by the Mini2
2- During this first flight I lost the connection between the Mini2 and the controler a couple of times even I was at 500meters (in open air), and got it back a few seconds after each time. So I tried to test the smart RTH and it worked. Tonight I looked in user manual at the RTH Failsafe. AND a sentence is confusing me "The aircraft will fly backwards for 50 m on its original flight route and ascend to the preset RTH altitude to enter Straight Line RTH. The aircraft enters Straight Line RTH if the remote controller signal is restored during Failsafe RTH", but what is happening IF the signal is NOT restored ? Does-it continue to fly back to Homepoint ?

Thanks in advance to all

UAV is "user" configurable. It may be set to a higher # of sats that you can change to 10. I would not fly with less, but possible depending on my location and IF I can get a sat lock at all. I rarely fly in clear wide open areas; so have gotten used to a procedure where I launch the drone, hover for a a few seconds and if no Home Point set, I will move to an opening and climb to the DJI max of 98 feet to try and get a sat lock. Have had a time or two when that did not work either - so flew the drone for my shots and brought it home.

RTH is that - a failsafe. I do not depend on it, but it's nice to have and when it kicks in when you lose signal - depending on where you are flying and the terrain around you. I have mine set to climb to like 300 feet before returning home - to clear trees and other obstacles that may be along the flightpath.

500 meters seem low to lose signal in a wide open area, but it does happen. One thing that UAV also has is the kp index. If it reaches a certain point - too much magnetic activity may be present and THAT WILL affect your signal.

For info on kp - check out this website.

Planetary K-index | NOAA / NWS Space Weather Prediction Center

www.swpc.noaa.gov

 

[photo2be]

UAV is "user" configurable. It may be set to a higher # of sats that you can change to 10. I would not fly with less, but possible depending on my location and IF I can get a sat lock at all. I rarely fly in clear wide open areas; so have gotten used to a procedure where I launch the drone, hover for a a few seconds and if no Home Point set, I will move to an opening and climb to the DJI max of 98 feet to try and get a sat lock. Have had a time or two when that did not work either - so flew the drone for my shots and brought it home.

RTH is that - a failsafe. I do not depend on it, but it's nice to have and when it kicks in when you lose signal - depending on where you are flying and the terrain around you. I have mine set to climb to like 300 feet before returning home - to clear trees and other obstacles that may be along the flightpath.

500 meters seem low to lose signal in a wide open area, but it does happen. One thing that UAV also has is the kp index. If it reaches a certain point - too much magnetic activity may be present and THAT WILL affect your signal.

For info on kp - check out this website.

Planetary K-index | NOAA / NWS Space Weather Prediction Center

www.swpc.noaa.gov

Hi Tlswift! Can you pls clarify the difference, if any, between sats "found" on the screen and sats locked! I know that it is a difference but I am sure you can't confirm it.

 

[tlswift58]

Hi Tlswift! Can you pls clarify the difference, if any, between sats "found" on the screen and sats locked! I know that it is a difference but I am sure you can't confirm it.

Would say only item you need to be concerned about is LOCK. That is what your drone works off of.

I have noticed when looking at UAVForecast - where I live - North GA / Western NC / Upstate SC - that from about 2:15 / 2:30 pm to 3:30'ish every day - sats drop below 10, which registers as a 'do not fly." I have flown during that time and never had any issues with my Air2.

 

[photo2be]

Would say only item you need to be concerned about is LOCK. That is what your drone works off of.

I have noticed when looking at UAVForecast - where I live - North GA / Western NC / Upstate SC - that from about 2:15 / 2:30 pm to 3:30'ish every day - sats drop below 10, which registers as a 'do not fly." I have flown during that time and never had any issues with my Air2.

My question was: How to you see/know that the sats are LOCKED not only found?

 

[Thomas B]

My question was: How to you see/know that the sats are LOCKED not only found?

If they are registered as found by your equipment they are “locked”

 

[photo2be]

If they are registered as found by your equipment they are “locked”

Ok, are you sure that the GPS "almanack" is 100% updated when you see the sats nbr on the screen?

 

[Thomas B]

Ok, are you sure that the GPS "almanack" is 100% updated when you see the sats nbr on the screen?

Yes....

 

[photo2be]

Yes....

So there is no reason to idle on the ground for approx. 12minutes if you haven't been in the air for lets say 2 weeks even if you SEE enough nbr of sats?

 

[Thomas B]

So there is no reason to idle on the ground for approx. 12minutes if you haven't been in the air for lets say 2 weeks even if you SEE enough nbr of sats?

Hover at 10-20’ for as long as it takes to acquire the satellites in your particular location.

 

[photo2be]

Hover at 10-20’ for as long as it takes to acquire the satellites in your particular location.

acquire = lock?

 

[Meta4]

Ok, are you sure that the GPS "almanack" is 100% updated when you see the sats nbr on the screen?

First .. forget about UAV forecast with respect to satellites.
It won't give you any useful imformation and will only confuse you more.
No matter where you are in the world or when, you will always have many more sats than you need for flying .. as long as your drone is out in the open with an unobstructed skyview.

Your drone will do all that's needed and let you know when it has acquired enough satellites to record a home point.

 

[Thomas B]

acquire = lock?

Same

 

[Wyvern]

Hi everybody, I'm new here and new to drones as well. Thank you for accepting me in your community. I think that the Mini 2 can lock on to all 3 GPS systems, namely the US GPS, the Russian Glonass and the European Galileo satellites. The UAV app might not include all 3 systems. In my location the app was predicting 11.9 satellites. I had 19 on the ground and 25 at a height of 10 metres. It took maybe all of 10 seconds to acquire them. So I would not rely too much on the UAV app for satellite prediction. I tried a full RTH and the drone landed within 20cm from the takeoff spot. BTW, I tried to take a screenshot when airborne and turned off the smartphone by mistake. The drone just hovered and I regained control when I turned the phone back on.

 

[Luckyguy9]

Hi MM2 pilots
I had my first flight today, and thanks to all your advices,.. it went fine.... but tI will keep practicing and updating my checklist.
I have 2 questions :
1- Minimum number of GPS satellites : When I checked on the UAV app, I had only 10 sats,.. and it was in RED status and because of this it was "No good to flight", but the DJI app saif it was OK to fly. So maybe the UAV app was not tuned correctly, that is why I would to know what is the minimum number of satellites required by the Mini2
2- During this first flight I lost the connection between the Mini2 and the controler a couple of times even I was at 500meters (in open air), and got it back a few seconds after each time. So I tried to test the smart RTH and it worked. Tonight I looked in user manual at the RTH Failsafe. AND a sentence is confusing me "The aircraft will fly backwards for 50 m on its original flight route and ascend to the preset RTH altitude to enter Straight Line RTH. The aircraft enters Straight Line RTH if the remote controller signal is restored during Failsafe RTH", but what is happening IF the signal is NOT restored ? Does-it continue to fly back to Homepoint ?

Thanks in advance to all

Check the UAV Forcast software for location. Don’t assume it is providing info for your location. I’m in Long Island and mine defaults to someplace in Connecticut. Either manually enter your zip cose in location bar or buy the yearly subscription that allows you to save any location as default.
As best as I know from my phantom 3A, if connection is lost from controller, it Simply returns to home point.

 

[Bodkin's Best Photography]

Check the UAV Forcast software for location. Don’t assume it is providing info for your location. I’m in Long Island and mine defaults to someplace in Connecticut. Either manually enter your zip cose in location bar or buy the yearly subscription that allows you to save any location as default.
As best as I know from my phantom 3A, if connection is lost from controller, it Simply returns to home point.

I believe it is signal loss exceeding 12 seconds that initiates rth.

 

[DJayI]

it Simply returns to home point

If I recall correctly, there are settings in the DJI Fly app that give the option to RTH(default) , land or hover. So one might want to check those.

 

[Meta4]

Check the UAV Forcast software for location. Don’t assume it is providing info for your location. I’m in Long Island and mine defaults to someplace in Connecticut.

It's a waste of time looking at UAV for GPS sat predictions.
Wherever you are in the world and whenever you want to fly, there will always be many more sats than you need.

 

[Welsh m4vic]

The absolute minimum is 6 sats, but you will usually require more because there's more to it than a simple number.
The sats have to be well spread around the sky to provide good satellite geometry necessary for accurate location data.


There's no "tuning" or any configuring that would make any difference.
If your drone is out in the open with a clear, unobstructed skyview, you'll always have plenty of sats and no problems with GPS.
If you launch from a place where trees, buildings etc block large parts of teh sky, the drone will take longer to get good GPS data (or might not if too much of the sky is blocked).

The wording in the manual is confusing and the actual meaning is not clear.
It's likely to be poorly written and/or a bad translation.

With previous DJI drones that could retrace their path after signal loss, the drone would cease flying backwards if signal was regained and the operator could resume flying normally.
If signal was not regained, then the drone would enter straight line RTH.

Having it work that way is probably the most sensible way for DJI to have programmed it.
I'd suggest a little testing in a large, open area to see what really happens.
Fly out >20 metres, switch off the controller and observe what the drone does.