How many satellites?

[A.O.]

So how many satellites do I need locked in to fly? I have a MA2 if that makes any difference.

I have that UAV Forecast app so I always check flying conditions first before I fly, BUT, Like right now it says 9.1 Sats locked and its NOT GOOD TO FLY. Its sunny and nice a little breezy (gusts to 16mph at 100 feet) and everything but the Sats is good to go.

So how many locked do I need, ad what about this KP? Does it really matter?

Thanks

 

[Thomas B]

I believe a minimum of 8 is OK.

 

[Camino Ken]

The impact of Kp index is very overblown. It is extremely rare that it causes any problems. Absolute worst case it can interfere with a couple of satellites but unless you are very near one of the poles of the earth it won’t make any difference.

Below is something I posted a while ago if you want more information.

Kp index is an indicator of geomagnetic storms in the ionosphere. According to NOAA (NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION) “The principal users affected by geomagnetic storms are the electrical power grid, spacecraft operations, users of radio signals that reflect off of or pass through the ionosphere, and observers of the aurora.”

In the case of drones I believe that the only thing affected is GPS. I was able to find a scientific paper that analyzed the effect of these geo storms on GPS signals and it concluded that it affected the RMS positioning accuracy. The numbers ranged from 0.393m to 1.051m from a mild to a severe magnetic storm. With no storm the number is 0.167m.

You can draw your own conclusions but I think it will have minimal to no affect on drone flying. Worst case is that you can lose the connection to individual satellites so that if you ensure you have the minimum number of total satellites your probably OK.

if your interested you can read the paper here. Assessing the Performance of GPS Precise Point Positioning Under Different Geomagnetic Storm Conditions during Solar Cycle 24

 

[old man mavic]

the number of sats will vary in any 24 hour period depending where you are located
if the drone is happy with the number then it will tell you with the screen and the home point message , most times the number will vary from say ten to 20 plus its important not to get air born till you have the go ahead from your device

 

[KLAX]

Hello AO, I usually hang around in the "Commercial" section of this site, but wanted to share some of our best practices.
Full disclosure: I don't own or use any other Mavic except the 2 Pro, but hopefully assuming the behavior will be the same for any in the Mavic line. Happy to be checked/corrected on this if not accurate. I also am not familiar at all with the DJI FLY C2 software (FCS), so full disclosure.

First, I'd suggest getting rid of the UAV forecast app in favor of another more reliable weather information service like Weather.GOV. The UAV Forecast app regularly provides misleading information to pilots that may rely on it too much. (Example: Cloud Cover - Do Not Fly. What??). No app is going to replace what's between your ears regarding GO/NO-GO risk based decision making.

• Our internal guidance re: satellite connectivity is a minimum of 6 satellites connected, but we may still have visible instability issues depending on "where" those satellites are located (what is the spread up there?)
  
  
• KP Index seems to be a massive myth with regard to affect on satellite connectivity and signal strength. If solar activity was contributing to reductions or outages in GPS signal strength, the news channels would be flooded with reports of drones falling out of the skies all over the globe. Kp Index should not have any affect on your internal compass either.
  
  
• Assuming that the "Air" series connects to the same satellites as everything else in the Mavic line, or other DJI vehicles. This means you have GPS (U.S.A.) as well as GLONASS access. You should rarely see less than 9 or 10 satellites connected.
  
  
• Risk Assessment and Mitigation: You have no control of satellite connectivity but you do have control on whether to fly or not; and how you'll fly (altitude, distance, etc.). Make a judgement call on the day-of, and make sure your vehicle is behaving within your acceptable limits and skills, and you'll be good to go! Sometimes you can wait an hour, or reboot your systems (radio/uav), and things will look differently (better).
  
  
• Last thing, and it rarely affects us all, but the FAA's Safety Team (FAST) will allow you to make an account and get notifications regarding GPS testing that may be occurring in your area. Here is a link to an example notification

Hope this helps a little
Safe Flying!

 

[Camino Ken]

Hello AO, I usually hang around in the "Commercial" section of this site, but wanted to share some of our best practices.
Full disclosure: I don't own or use any other Mavic except the 2 Pro, but hopefully assuming the behavior will be the same for any in the Mavic line. Happy to be checked/corrected on this if not accurate. I also am not familiar at all with the DJI FLY C2 software (FCS), so full disclosure.

First, I'd suggest getting rid of the UAV forecast app in favor of another more reliable weather information service like Weather.GOV. The UAV Forecast app regularly provides misleading information to pilots that may rely on it too much. (Example: Cloud Cover - Do Not Fly. What??). No app is going to replace what's between your ears regarding GO/NO-GO risk based decision making.

• Our internal guidance re: satellite connectivity is a minimum of 6 satellites connected, but we may still have visible instability issues depending on "where" those satellites are located (what is the spread up there?)
  
  
• KP Index seems to be a massive myth with regard to affect on satellite connectivity and signal strength. If solar activity was contributing to reductions or outages in GPS signal strength, the news channels would be flooded with reports of drones falling out of the skies all over the globe. Kp Index should not have any affect on your internal compass either.
  
  
• Assuming that the "Air" series connects to the same satellites as everything else in the Mavic line, or other DJI vehicles. This means you have GPS (U.S.A.) as well as GLONASS access. You should rarely see less than 9 or 10 satellites connected.
  
  
• Risk Assessment and Mitigation: You have no control of satellite connectivity but you do have control on whether to fly or not; and how you'll fly (altitude, distance, etc.). Make a judgement call on the day-of, and make sure your vehicle is behaving within your acceptable limits and skills, and you'll be good to go! Sometimes you can wait an hour, or reboot your systems (radio/uav), and things will look differently (better).
  
  
• Last thing, and it rarely affects us all, but the FAA's Safety Team (FAST) will allow you to make an account and get notifications regarding GPS testing that may be occurring in your area. Here is a link to an example notification

Hope this helps a little
Safe Flying!

FYI - Kp index isn’t a myth but it is almost. See my post above.

 

[msinger]

So how many locked do I need

DJI Fly will tell you when it's safe to take off. That won't occur until the drone has connected to enough satellites.

what about this KP? Does it really matter?

Nope. You can disregard it.

 

[Meta4]

So how many satellites do I need locked in to fly?

DJI won't allow your drone to go into GPS Mode with less than 6 sats, but depending on the spread of the satellites, it may need more.

I have that UAV Forecast app so I always check flying conditions first before I fly, BUT, Like right now it says 9.1 Sats locked and its NOT GOOD TO FLY. ... but the Sats is good to go.

UAV forecast isn't really much use, particularly with some of their default settings.
If it's telling you there are only 9 sats in your sky, it's only telling you about US GPS sats.
But your drone also receives signals from Russian Glonass sats, so it will often pick up 20 or more sats.
If the drone has a good unobstructed view of most of the sky, you will always have more than enough satellites.

 

[jarnie]

I believe that when the number of satellites is displayed it displays them in a colour which indicates how safe. Eg in red then not enough satellites, white all ok.

 

[A.O.]

DJI won't allow your drone to go into GPS Mode with less than 6 sats, but depending on the spread of the satellites, it may need more.

UAV forecast isn't really much use, particularly with some of their default settings.
If it's telling you there are only 9 sats in your sky, it's only telling you about US GPS sats.
But your drone also receives signals from Russian Glonass sats, so it will often pick up 20 or more sats.
If the drone has a good unobstructed view of most of the sky, you will always have more than enough satellites.

I happen to like the UAV forecast, nothing is perfect but it at least gives me a basic rundown... and yes it includes the Glonass sats, Galileo sats too.

 

[Meta4]

and yes it includes the Glonass sats, Galileo sats too.

If the app is forecasting only 9 sats in your sky, it's not showing GPS + Glonass + Galileo
You'd get 9 GPS sats anywhere, any time.
You may have to adjust the default settings if you want to show more.
But as I mentioned, you don't need an app to forecast the number of sats in your sky because there will always be many more than you need.

 

[A.O.]

If the app is forecasting only 9 sats in your sky, it's not showing GPS + Glonass + Galileo
You'd get 9 GPS sats anywhere, any time.
You may have to adjust the default settings if you want to show more.
But as I mentioned, you don't need an app to forecast the number of sats in your sky because there will always be many more than you need.

Depends on when.. right now I have 21.8 sats locked. But gusts up to 35 so I'm not flying right now anyway..

I had to go in and turn the Glonass and Galileo on.

 

[Meta4]

Depends on when.. right now I have 21.8 sats locked. But gusts up to 35 so I'm not flying right now anyway..

I had to go in and turn the Glonass and Galileo on.

Since the Air 2 doesn't receive Galileo sats, it won't help to know how many of them are in your sky.
But you don't need to rely on UAV Forecast for satellite numbers as there will always be plenty more than you need, wherever you are.

 

[Repaid1]

Depends on when.. right now I have 21.8 sats locked. But gusts up to 35 so I'm not flying right now anyway..

I had to go in and turn the Glonass and Galileo on.

As said it doesn't matter what third party app sees, it matters what your drone sees and if it says you can fly, then you can...don't make it harder than need be. What DJI App says is all that matters.

 

[kpjamro]

if your interested you can read the paper here. Assessing the Performance of GPS Precise Point Positioning Under Different Geomagnetic Storm Conditions during Solar Cycle 24

This paper describes PPP (GPS precise point positioning). DJI does not use PPP. DJI have stated that typical (absolute) accuracy is +/- 5 meters horizontally.