minimum amount of locked satellites to fly?

[Bogey]

Hey folks,

I'm having a tough time finding the minimum amount of locked satellites to safely fly? Perhaps I can't find it because it's a personal choice?? If that's the case, what do most folks go with.

My UAV forecast shows 11.9 locked satellites, but says "Not Good To Fly"?

Thank you,

Bogey

 

[Anthony Horrigan]

Minimum 15 satellites, is my rule and never had any issues.

 

[beachcombing]

Well, you are mixing your metaphors, so to speak.

The number of "locked satellites" in UAV forecast has nothing to do with how many satellites your Mavic may or may not be connected to.

Also, the "Not Good to Fly" "determination in the app is based on the thresholds that YOU set. Which parameters in the app are showing as being in red vs. green? What thresholds do you have set in the app?

Now, as to the number of locked satellites showing in the DJI Go 4 app, typically I look to have 12 or more locked which is typically not a problem to obtain for me.

 

[BD0G]

Some regions of the world like India only have 7 GPS satellites available so it would be impossible to connect to more than 7 in that region.

Indian Regional Navigation Satellite System - Wikipedia

 

[Big Fil]

How many satellites you need to safely fly all depends on the pilot. Some people have the skills to safely fly a mavic with zero satellites. Because you are asking i'm going to assume you will be relying on GPS assistance to fly. In that case i'd say wait for DJI go to give you the green Safe to Fly message in GPS screen.

 

[Big Fil]

How many satellites you need to safely fly all depends on the pilot. Some people have the skills to safely fly a mavic with zero satellites. Because you are asking i'm going to assume you will be relying on GPS assistance to fly. In that case i'd say wait for DJI go to give you the green Safe to Fly message in GPS status message at the top of the screen.

 

[Howcroft22]

How many satellites you need to safely fly all depends on the pilot. Some people have the skills to safely fly a mavic with zero satellites. Because you are asking i'm going to assume you will be relying on GPS assistance to fly. In that case i'd say wait for DJI go to give you the green Safe to Fly message in GPS screen.

Exactly. I think 10 should be the minimum.

 

[Bogey]

Thanks guys!! I was always getting a "not good to fly" until another member kindly explained the "thresholds" to me, and I found it was my temperature setting that was stopping before....

NOT knowing, I had my satellite threshold set at 10, and right now my UAV is saying no go and it's showing 11.9 locked satellites as the reason I'm getting the "no fly".

I've been sicker than a dog for 3 weeks with flu/cold and I'm finally "better" and the sun came out and I really, really wanted to fly (I have been reading the forums, watching youtube videos and I finally printed out the manual, but obviously I haven't retained it all yet because I could NOT find the darn minimum sats required)

Was just hoping for a quick flight, but I don't want to make a stupid mistake (LOL, read too many fly away threads while sick!)

Anyway, thanks for the input - always appreciated!

Bogey (BTW, I am NOT a good pilot - new guy = 23 flights)

 

[Mossiback]

I am not familiar with the term "locked satellites". The GPS satellites are in a low earth orbit and are constantly moving overhead so the number that the Mavic picks up will fluctuate over time and due to ground interference (buildings, canyons, etc).

 

[Tommytucka]

I don’t fly with less than 10 locked sats

 

[Dragonfly]

Some regions of the world like India only have 7 GPS satellites available so it would be impossible to connect to more than 7 in that region.

Indian Regional Navigation Satellite System - Wikipedia

India has exactly the same amount off satalites as the rest of the world.
The Mavic uses US and GLONASS system which for US has a total 24 sats (6 on 4 axis planes) that rotate around the globe. This puts at least a minimum of 8 sats in view at any one time at any point on earth of which only 3 are required for a fix (4 for 3D height) now add in the Russian GLONASS sats and you have 48 plus a couple of spares. Rotating on their axis plains giving your Mavic access upto 20 at any one time that may in view from any point on earth.

India that you refer to is sending up its own GPS satalite system called IRNSS and at moment only 7 are accessible or in view for India along with 2 ground stations.

There are also other GPS sat systems up there as well.

 

[Will.i.am]

I am not familiar with the term "locked satellites". The GPS satellites are in a low earth orbit and are constantly moving overhead so the number that the Mavic picks up will fluctuate over time and due to ground interference (buildings, canyons, etc).

GPS satellites fly in medium Earth orbit (MEO) and complete 2 orbits a day. The number of satellites being received is probably not as important as gps health, which is a combination of signal strength and sat orientation. Gps health determines whether or not your mavic goes into ATTI mode. You could probably have good gps health with 3 or 4 strong satellites oriented properly to give a 3D fix. But of course, the more sats received, the greater likelihood that they will produce a good fix and thus better gps health.

 

[beachcombing]

I am not familiar with the term "locked satellites". The GPS satellites are in a low earth orbit and are constantly moving overhead so the number that the Mavic picks up will fluctuate over time and due to ground interference (buildings, canyons, etc).

The UAV Forecast app has a setting that "estimates" the number of expected GPS satellites you might be able to connect with.

UAV Forecast

Q. What is the "Est. GPS Sats Locked" column?

UAVForecast.com uses a proprietary model to simulate the expected number of GPS satellites you will be able to lock, given the following factors:

• The number of GPS satellites visible in the sky (filtered by the elevation mask).
• The time of day: ionospheric interference with GPS is worse at night.
• Your latitude and longitude: ionospheric interference is worse close to the equator.
• The current or forecast Kp index.

Note that the estimate is just that - an estimate - and the actual number you see will vary according to local conditions, random fluctuations in the ionosphere, and so on.

 

[BlakPhoenix]

It all depends how stable you want the Mavic to be. The less satellites, the more it will drift in flight. I have flown with as few as 7 and there was noticeable sway while flying. The Mavic did well holding itself on the horizontal plane, but on the vertical plane the Mavic would bob up and down by up to a meter and a half on a continual basis (I should mention, this was above VPS range, which would probably have helped if it were available).

 

[Lapeer20m]

11

I arbitrarily choose to not launch unless mavic is connected to 11 satellites.

 

[BD0G]

India has exactly the same amount off satalites as the rest of the world.
The Mavic uses US and GLONASS system which for US has a total 24 sats (6 on 4 axis planes) that rotate around the globe. This puts at least a minimum of 8 sats in view at any one time at any point on earth of which only 3 are required for a fix (4 for 3D height) now add in the Russian GLONASS sats and you have 48 plus a couple of spares. Rotating on their axis plains giving your Mavic access upto 20 at any one time that may in view from any point on earth.

India that you refer to is sending up its own GPS satalite system called IRNSS and at moment only 7 are accessible or in view for India along with 2 ground stations.

There are also other GPS sat systems up there as well.

Thank you very much for this VERY informative post! I learned alot!

 

[Callum]

It all depends how stable you want the Mavic to be. The less satellites, the more it will drift in flight. I have flown with as few as 7 and there was noticeable sway while flying. The Mavic did well holding itself on the horizontal plane, but on the vertical plane the Mavic would bob up and down by up to a meter and a half on a continual basis (I should mention, this was above VPS range, which would probably have helped if it were available).

I don't think Mavic uses GPS for altitude. It uses barometric sensor and VPS.

Shouldn't make a difference how many satelites you have in holding altitude.

 

[okw]

I am not familiar with the term "locked satellites".

Expanding on what the others have said ... GPS receivers, whether in the Mavic, your car, or a handheld unit, use the signal transmitted from the GPS satellite to determine the distance from the satellite to the receiver. Given enough information from enough satellites, the receiver can then calculate its 3-dimensional location on earth.

Just because the receiver can "see" a satellite, doesn't mean that it has received an adequate signal to calculate the distance from that satellite. Once this distance is accurately calculated, it is said to have locked onto that satellite.

Additionally, when an accurate location has been calculated by the receiver, many GPS users say that they have a good satellite lock.

 

[BlakPhoenix]

I don't think Mavic uses GPS for altitude. It uses barometric sensor and VPS.

Shouldn't make a difference how many satelites you have in holding altitude.

Barometers are not precise enough to give altitude tracking down to the precision the Mavic is able to obtain on their own. The Mavic uses all of its sensors in combination to get super precise measurements of it's position, including the barometer, GPS, accelerometers, thermometers and (when close to the ground) VPS.

When you take out part of that puzzle (GPS) you greatly reduce the accuracy of all positioning data, including height. Depending on the relative location of the satellites available, this will determine which dimensions are lacking precision.

 

[sar104]

India has exactly the same amount off satalites as the rest of the world.
The Mavic uses US and GLONASS system which for US has a total 24 sats (6 on 4 axis planes) that rotate around the globe. This puts at least a minimum of 8 sats in view at any one time at any point on earth of which only 3 are required for a fix (4 for 3D height) now add in the Russian GLONASS sats and you have 48 plus a couple of spares. Rotating on their axis plains giving your Mavic access upto 20 at any one time that may in view from any point on earth.

India that you refer to is sending up its own GPS satalite system called IRNSS and at moment only 7 are accessible or in view for India along with 2 ground stations.

There are also other GPS sat systems up there as well.

That's a relief - this thread was becoming painful to read. On the question of number required, while it's true that 4 is theoretically enough for a 3-D fix, none of the DJI FCs will enter P-GPS mode with fewer than 7, and GPS health drops to zero at or below 6.