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My GF recently stated that when she drives from CA to AZ, along a stretch that crosses Zion her TomTom does not work (goes into "Searching for signal..." mode) because she doesn't have any cell reception. I told her that this must mean there is something wrong with her TomTom as GPS is supposed to work as long as you have an open view of the sky and it does not rely on cell coverage (obviously since people rely on satellite phones when they have no cell service!).
She insists that GPS does not work well in remote areas which I argue is totally false. Does anyone know what she is talking about? Or am I mistaken?
Did this happen one time or has it been repeatable? You sound correct in your comments to her. Wondering if it was just an electronic anomaly or something.
repeatable, I am thinking the only explanation is that she is driving through some kind of canyon but then she said no...the sky was open which is really puzzling.
As you said in your prior post, GPS signals depend in "line of sight," meaning that there must be an unobstructed view of the sky between the car and the satellites. Even if the sky directly above the GPS unit is clear, it's very common to loose GPS reception in areas that have tall trees or buildings on one or both sides of the road, since signals from satellites that are near the horizon can blocked by even short trees. These barriers can also cause problems with cell phone reception. My guess is that she is loosing reception due to a line of sight issue. It's possible that there are not enough visible satellites to get a good fix (several satellites are needed for a fix, not just one,) but this is pretty rare nowadays, given the number of GPS satellites that are in orbit.
As you said in your prior post, GPS signals depend in "line of sight," meaning that there must be an unobstructed view of the sky between the car and the satellites. Even if the sky directly above the GPS unit is clear, it's very common to loose GPS reception in areas that have tall trees or buildings on one or both sides of the road, since signals from satellites that are near the horizon can blocked by even short trees. These barriers can also cause problems with cell phone reception. My guess is that she is loosing reception due to a line of sight issue. It's possible that there are not enough visible satellites to get a good fix (several satellites are needed for a fix, not just one,) but this is pretty rare nowadays, given the number of GPS satellites that are in orbit.
4 is enough for a fix. The last time I checked there were (since 1995) 24 sats in the US GPS system.
This may explain an issue I've had traveling for work. Data service on my cell dropped out, and both my handheld and laptop GPS's went a little nuts for a few miles on the same stretch.
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