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GPS - not always the same?

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Hi Everyone and Merry X-mas!

I hope to find a GPS expert here as I have question.

Today I was flying exactly at the same spot but this time I got about 5-6 satellites less (only 12-14 instead 18-20) on the ST16 and also the Typhoon showed about 4 less.

How can this be? Shouldn't I see the same amount of satellites when being at the same location?

Can clouds (today it we had a thin coverage of clouds) decrease the amount of connectable GPS satellites?

Thanks and cheers

Tiburon
 
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No, not necessarily. Not only does location matter, time of day, which satellites are in view, if the satellites are functioning correctly, space weather, local weather all play into the equation.

GPS satellites are not "stationary"....

Hi Everyone and Merry X-mas!

I hope to find a GPS expert here as I have question.

Today I was flying exactly at the same spot but this time I got about 5-6 satellites less (only 12-14 instead 18-20) on the ST16 and also the Typhoon showed about 4 less.

How can this be? Shouldn't I see the same amount of satellites when being at the same location?

Can clouds (today it we had a thin coverage of clouds) decrease the amount of connectable GPS satellites?

Thanks and cheers

Tiburon
 
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Rayray

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QB is quite correct, as usual.
I'm no GPS expert, but in my experience, besides being in the same place, it needs to be the same time of day, and the space weather between the GPS Sats and you need to be roughly the same. (Solar wind, geomagnetic surges, etc. Search K or Kp factor)

Could you have reversed the count of the ST16 and the H? I think it is usual that the craft reads more GPS Sats than the ST16, and faster.
 

CraigCam

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Hi Everyone and Merry X-mas!

I hope to find a GPS expert here as I have question.

Today I was flying exactly at the same spot but this time I got about 5-6 satellites less (only 12-14 instead 18-20) on the ST16 and also the Typhoon showed about 4 less.

How can this be? Shouldn't I see the same amount of satellites when being at the same location?

Can clouds (today it we had a thin coverage of clouds) decrease the amount of connectable GPS satellites?

Thanks and cheers

Tiburon
Fortunately, the ST 16 tells us what locks there are and once it has enough, allows GPS lock start and features. Before all this sophisticated information we just trusted the only thing we had which was one light glowing solid and a beep upon lock. But once you saw that solid light, away you'd go with confidence. My point is we had no idea how many satellites we had so we could not worry about it. Now we can see what's up which can be a blessing or a curse depending on how you choose to interpret that info. Don't let false flags shake your confidence. Instead of flying, you'll be constantly thinking there is a problem and limit your job or fun. I only worry about GPS not working reliably on heavy overcast days, areas without unrestricted views of the sky, or high KP index.


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Hi Everyone and Merry X-mas!

I hope to find a GPS expert here as I have question.

Today I was flying exactly at the same spot but this time I got about 5-6 satellites less (only 12-14 instead 18-20) on the ST16 and also the Typhoon showed about 4 less.

How can this be? Shouldn't I see the same amount of satellites when being at the same location?

Can clouds (today it we had a thin coverage of clouds) decrease the amount of connectable GPS satellites?

Thanks and cheers

Tiburon
There are always diff..nbrs of sats in the same place and diff. times. Here you can see exactly how many where you live and at certain time!

Visibility
 
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Here's a handy tool that will tell you what you can expect as far as GPS satellites each day. You can customize it to determine if it is safe to fly based on other factors such as temperature as well: UAV Forecast
 

PatR

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GPS position also drifts a little with time as satellites transition their "viewable" window. You can see the effect of this if you allow a flight to maintain a stationary hover from start to end of a flight. This is present even with the best positioning systems available.

Far more important than number of satellites is the lock time for each satellite in view. Positional accuracy increases with lock time. If lock times are adequate good GPS reference can be had with as few as 4 or 5 satellites. The Yuneec H system has a default quantity requirement built into it, and a warning for when what it receives is not sufficient for accurate positioning. Angle mode is the "go to" for when this condition occurs.


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GPS position also drifts a little with time as satellites transition their "viewable" window. You can see the effect of this if you allow a flight to maintain a stationary hover from start to end of a flight. This is present even with the best positioning systems available.

Far more important than number of satellites is the lock time for each satellite in view. Positional accuracy increases with lock time. If lock times are adequate good GPS reference can be had with as few as 4 or 5 satellites. The Yuneec H system has a default quantity requirement built into it, and a warning for when what it receives is not sufficient for accurate positioning. Angle mode is the "go to" for when this condition occurs.


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How do you determine when you are safe to go / safe to fly more than that you see nbr of sats? How do you see they are "locked"?? Except the solid purple ofcourse.
 
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PatR

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Unfortunately, with our equipment you can't. Consumer equipment is designed for users, not techie or DIY types. There's good reason to never rush a take off. Allowing a few moments for GPS to stabilize is one of them. More often than not you'll see satellite count increase on either the -16, aircraft, or both if you are willing to wait a minute or so.
 
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Unfortunately, with our equipment you can't. Consumer equipment is designed for users, not techie or DIY types. There's good reason to never rush a take off. Allowing a few moments for GPS to stabilize is one of them. More often than not you'll see satellite count increase on either the -16, aircraft, or both if you are willing to wait a minute or so.
Thanx, do you say that the nbr of sats shown on the H and -16 always are locked? When I have a solid purple (with a very short green, or white? flash in it) I thought the sats were locked? Right? Wrong?
 

CraigCam

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Thanx, do you say that the nbr of sats shown on the H and -16 always are locked? When I have a solid purple (with a very short green, or white? flash in it) I thought the sats were locked? Right? Wrong?
The solid purple white flash indicates you have enough satellites between st and h to do follow me/watch me.


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PatR

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Craig is correct. I was referring to being able to view satellite/GPS specifics, such as the sat ID, HDOP, and lock time.
 
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Here is another good place to check out

Location Lookup
Thank you Augustine,

This is a very useful webpage and it shows that when I went flying a "minimum" of satellites was reached. I also tells me that the number of satellites that are locked are GPS and GLONASS together (which makes sense). The max and min amount of satellites is also very well matching with my experience.

I have the impression with less than 14 satellites locked the, Typhoon is not flying as precisely as with 18 and is always drifting a little bit to find its "place in space". This makes it a little bit tricky to maneuver close to trees especially when there is noticeable wind.

Cheers

Tiburon
 
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Here is an excellent GPS app for your phone, provides a wealth of GPS information, number, in-view, in-use, status, accuracy, etc. Just a suggestion to compare what you H/16 are seeing vs what is available for your location and time.

GPS Test - Android Apps on Google Play
 
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Thanx Johm D, but can't find it when I search in (Iphone) Apple Store? Happy 2017!
 
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Sorry you could not find it with Apple, You might try searching for GPS locator or GPS status. Maybe they have a similar app. Good Luck and a Happy 2017 Flying Year to you.
 

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