green ball or green bars?

[rgleason]

GPS Setup and Status
I hope that does it. Scribe.

[hellosailor]

r.v.-
I recall a conversation long ago in another forum about GPS instruments and the varying algorithms they may use to actually develop a "position". And the folks at Garmin got very paranoid and hostile about being asked which choices they were making. Among other things, you need computer horsepower for advanced calculations or rapid (parallel or rapid serial) calculations, and that means more expensive chips. GPS makers don't like to talk about the trade-offs they may have made, so even with the same number of satellites being visible, results may vary. Perhaps less now than they used to.
IIRC the system only needs to see 3 satellites to give you a two-dimensional fix, and that would be "sufficient for navigation" since we are all at sea level, which is fairly uniform. My first GPS used to routinely tell me I was under 80 feet of water, that didn't bother me. You only *need* 4 satellites when you want to resolve your position in three dimensions, with altitude.
So in theory, with just 3 satellites and with a proper GPS computing from them, your position will indeed be good enough for ocean navigation. Bear in mind, that is good enough to be within the spec of the GPS system, and that allows for some meters of error within a certain percent of the time--it is not what you'd want for surveying.
It sounds like the green ball indicates this condition, while the green bars are fussing with things that shouldn't matter for general navigation. (i.e. 4 or more satellites, shouldn't be of general concern to sailors.)

Certainly sounds like something that could be combined, or clarified though.

[a64pilot]

Originally Posted by rgleason

Obviously, we would like to have "green ball" description correct.



Pavel: "They are exactly the same, the ball just means we get the position often enough, but we don't know how many satellites provide the position"

bcn: A GPS fix requires a minimum of 4 satellites to resolve the four unknowns
X,Y,Z (spatial) and t (time). Showing only one bar - 1-4 sats - the reception will not be very stable most probably.

Terry: As explained earlier, it means the GPS signal is not coming directly from the GPS (with it's additional collateral information) but from elsewhere, such as via an AIS device or network. At least that's my understanding.

Terry this is new to me... what should it be?

Actually I believe you can get a 2D fix with three satellites ( no altitude) but need four to get a 3D fix
https://www.maptoaster.com/maptoaste...gps-works.html