GPS & Fart-Smones

Feb 28, 2020 Last reply: 6 years ago 5 Replies

Hi,



In a Peugeot self help group a couple of people have suggested that domestic Sat navy and google maps on IOS, etc triangulate directly with gps satellites.



Is that really the case?



And if so, why do I need a dustbin lid to pick up Freesat?


There are numerous differences: the freesat satellite is nearly twice as far away as those for GPS, uses a much higher frequency, requires much higher bandwidths to name but a few. Apples and pears really when it comes to how the signal is received.

Did you not ask this already?

I'm not sure if you really don't know or are winding the group up! TV broadcast sats, are geostationary, in an orbit approx 25000 miles above the equator and rotate once in 24 hours. That is a long distance but at the moment is the only way that it can be done. GPS are very low down, and therefore much easier to pick up, but there are a huge number of them, each with their own atomic clocks and hence triangulation is very accurate because they are in orbits which are known and precise and basically the more the system can see the more accurate the triangulation. End of story. Brian

In a sense, yes. However it is a very sophisticated sort of triangulation. Direction is not available directly, but each satellite beamcasts exactly where it is, and when it is, and by use of very accurate clocks, the time lag to each satellite can be established.

knowing the distance to three or more satellites to a very high accuracy allows 3D placement of the receiver to be established.

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There is very little information in the GPS data, and its repeated many many times. And if it is lost for a few seconds now and again it is not critical.

That is not the case with broadcast TV signals

Field strength of the signal, for one thing. In the same way as you need a better aerial to pick up any distant transmission.

I may have asked before Brian.

In which case I apologise, the little grey cells aren?t what that once were.

Either way, it?s prompted some fascinating answers.

Cheers

All

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