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Satellite Tracking


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If the GPS rcvr. thought you were still in the UK, it would only be looking for satellites known to be above the horizon in the UK at that time. That normally makes the most efficient use of the 12 receiver circuits to get a lock as quickly as possible.

Thailand is far enough away that it's likely that no satellites visible in the UK were also visible in Thailand, so the receiver kept searching fruitlessly. Telling it about where it is lets it look for the appropriate satellites. Even just telling it that it's at a new unspecified location will help since then it'll look for all satellites and eventually find enough for a lock.

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Your Vista maintains an almanac on board that knows where the birds should be ant any given time, This is how when you turn your Vista on at home, it gets a lock in a few seconds. You see, it knows where you last were, and where the birds are at that instant, at that last location.


Now, you travel to the other side of the globe. (I assume you had not turned your GPS on until you got to Thailand). Your Vista starts looking for the birds thinking it is still in the UK. Not a single signal it receives seems to make sense to it.


If you were to leave it on for an extended period (could be 15 minutes or more), it will eventually determine that none of the satellites it is expecting to see are where it expects them to be and begin determining its new location. I would guess you gave up before the Vista was successful in this procedure.


You can jump start the process by telling it where you think you are. It will use its almanac as a starting point for what birds to look for and where, based on where you think you are. This should take it only a minute at most to get a lock. With a mapping GPSr, just search for a city near you, then set your new location at that city.

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