Satellites, Why So Few?

Joined
Oct 17, 2016
Messages
345
Reaction score
93
Age
69
Location
Upper Canada Village
Today a perfectly clear day and I went to my usual spot. This place is a wide open park with no buildings or other obstacles in my way. I fire up the controller and drone (P3S) along with Litchi app and wait. Best I could get was 8 satellites. Over the past 2 weeks in the same area the norm is 12 with a high of 13 and a (very seldom) low of 10.

I decided to try an other usual spot and see if there was any improvement. Here I got 9 satellites where the norm over the past few weeks was as above.

I decided to try my mobile app "GPS Test" to see what numbers I was getting at these location. In both case I would get readings of "16 in view, 14 in use" or "17 in view, 15 in use"

I cannot understand why today these numbers are so low. No way that previous days had better/clearer skies. Similar, maybe, but not better. So my questions are:

Does this drop in numbers suggest I need to recalibrate imu/compass/etc?
What happens if I am flying a Litchi mission and the satellite number drops below 8??? Does the mission stop and my drone drift away with the wind??
 
Joined
Feb 17, 2016
Messages
626
Reaction score
252
Age
24
I noticed exactly the same thing with my P3s yesterday Latest app with older FW
 

Mark The Droner

Premium Pilot
Joined
Aug 26, 2015
Messages
5,311
Reaction score
1,739
I will frequently launch with 7 or 8. 6 is rare. But the number always increases once I get up in the air. I remember once I was up 150 feet and still had 6 so I elevated some more and it jumped to 9. I'm not sure if I've ever completed a flight with less than 10. I've never had more than 13.

There is nothing wrong with 8 satellites or even 7. 6 Satellites you should be a little nervous because that's the bare bones minimum for GPS.

If you are down to 5 on a Litchi mission, it'll hover. But that's very rare. Usually you'd have to drop down into a hole or something for that to happen.
 

Meta4

Moderator
Staff Member
Premium Pilot
Joined
Jan 8, 2014
Messages
13,912
Reaction score
7,935
Today a perfectly clear day and I went to my usual spot. This place is a wide open park with no buildings or other obstacles in my way. I fire up the controller and drone (P3S) along with Litchi app and wait. Best I could get was 8 satellites. Over the past 2 weeks in the same area the norm is 12 with a high of 13 and a (very seldom) low of 10.

I decided to try my mobile app "GPS Test" to see what numbers I was getting at these location. In both case I would get readings of "16 in view, 14 in use" or "17 in view, 15 in use"
First point: GPS satellites aren't in fixed positions in the sky.
They are orbiting while the earth is rotating inside the "birdcage" they form around it.
This accounts for the variable numbers observed.

2. There are a few GPS systems with their own satellites.
Your Standard only picks up one type - the US GPS system
Your app is also picking up Russian satellites and showing you the total number.
This GPS app shows the US sats (low ID numbers) as circles and the Russian Glonass sats as squares.

Does this drop in numbers suggest I need to recalibrate imu/compass/etc?
What happens if I am flying a Litchi mission and the satellite number drops below 8??? Does the mission stop and my drone drift away with the wind??
Recalibrating your IMU and/or compass will have no effect on GPS issues and your Phantom can only see what is in your sky.
It is extremely unlikely that your Phantom will have less than 6 sats if it is in the air with a good view of the sky.
Fly under tree cover or in a canyon etc that blocks the Phantom's view of the sky and you will lose sats.
 
Joined
Feb 17, 2016
Messages
626
Reaction score
252
Age
24
I have a P3A and a P3S I will test both Theoretically they should register the same number of satilites at the one place at the same time .
 
Joined
Jan 3, 2016
Messages
742
Reaction score
302
Age
68
I have a P3A and a P3S I will test both Theoretically they should register the same number of satilites at the one place at the same time .
It's my understanding that the P3S doesn't receive data from GLONASS sats but the P3A does. If I'm correct, you'll get a much higher number on your P3A.

SB
 
  • Like
Reactions: Falcon900
Joined
Feb 17, 2016
Messages
626
Reaction score
252
Age
24
Ok I didn't realise that .The OP said he tested the number of satellites with his phone . Would that include the GLONASSsats
 
Joined
Jan 3, 2016
Messages
742
Reaction score
302
Age
68
Ok I didn't realise that .The OP said he tested the number of satellites with his phone . Would that include the GLONASSsats
It depends on the GPS chip in the phone.

Just re-read his post: "In both case I would get readings of "16 in view, 14 in use" or "17 in view, 15 in use"

His phone HAS to be getting GONASS data to get that many.

SB
 
Joined
Oct 17, 2016
Messages
345
Reaction score
93
Age
69
Location
Upper Canada Village
Thanks everyone for your feedback. Today is another clear sunny day. Going back to the same spots and try again.
 
Joined
Feb 19, 2016
Messages
149
Reaction score
40
Location
San Marcos, CA
First point: GPS satellites aren't in fixed positions in the sky.
They are orbiting while the earth is rotating inside the "birdcage" they form around it.
This accounts for the variable numbers observed.

2. There are a few GPS systems with their own satellites.
Your Standard only picks up one type - the US GPS system
Your app is also picking up Russian satellites and showing you the total number.
This GPS app shows the US sats (low ID numbers) as circles and the Russian Glonass sats as squares.


Recalibrating your IMU and/or compass will have no effect on GPS issues and your Phantom can only see what is in your sky.
It is extremely unlikely that your Phantom will have less than 6 sats if it is in the air with a good view of the sky.
Fly under tree cover or in a canyon etc that blocks the Phantom's view of the sky and you will lose sats.
Meta4, thank you for a complete and accurate post! That's so rare on forums of every kind. You saved me the trouble :) :)
 
  • Like
Reactions: Nellett
Joined
Dec 12, 2015
Messages
173
Reaction score
59
Location
Dallas, Texas
First point: GPS satellites aren't in fixed positions in the sky.
They are orbiting while the earth is rotating inside the "birdcage" they form around it.
This accounts for the variable numbers observed.

2. There are a few GPS systems with their own satellites.
Your Standard only picks up one type - the US GPS system
Your app is also picking up Russian satellites and showing you the total number.
This GPS app shows the US sats (low ID numbers) as circles and the Russian Glonass sats as squares.


Recalibrating your IMU and/or compass will have no effect on GPS issues and your Phantom can only see what is in your sky.
It is extremely unlikely that your Phantom will have less than 6 sats if it is in the air with a good view of the sky.
Fly under tree cover or in a canyon etc that blocks the Phantom's view of the sky and you will lose sats.
 
Joined
Dec 12, 2015
Messages
173
Reaction score
59
Location
Dallas, Texas
I was under the impression that GPS satellites are in geosynchronous orbits. This way, they have the appearance of being "stationary" .
Which is it?
 

N017RW

Premium Pilot
Joined
May 2, 2014
Messages
8,961
Reaction score
3,240
Location
Palm Beach Co.- FL
They are as Meta4 has posted... NOT Geosynchronous.

Can you do your own basic research?
 

Mark The Droner

Premium Pilot
Joined
Aug 26, 2015
Messages
5,311
Reaction score
1,739
I've been flying 15 months, roughly 200 flights/600+ miles and have never once had 14 satellites
 

New Threads

Forum statistics

Threads
136,147
Messages
1,408,113
Members
99,061
Latest member
snuffy