Should I “update” my Roadmate Magellan GPS

WTP-GC wrote:
I've heard the arguments of using a GPS device in lieu of a cell phone and vice versa. Yes, the cell phone does require a cell signal to work. However, the phones have a built in GPS (at least mine does). It's my understanding that you only need a cell signal to get going, but once underway and "navigating" the GPS function will continue to work without cell service. I've started navigating with my iPhone in a place that had service, but then drove through an area that absolutely doesn't have service, yet it functioned fine throughout.

If what you say is indeed true of how smart phone navigation works, then it sure needs to be explained and talked about way more by smartphone manufacturers and retailers.

That brings up a question - how many of you smartphone navigation users have ever had something like a "no satellite signal" message appear on the screen when trying to navigate out in areas where there also isn't any cell signal available?

A "no satellite signal" message of course should occur in such situations as when a cell phone is inside your RV away from the windows. That message sometimes appears on the screen of my Garmin navigator when it doesn't have line-of-sight satellite access - but I've never seen that kind of message appear on our smartphone ... which makes me doubtful of it uses satellite access for anything accept locating us if we can make a regular cell call for some kind of help.

pnichols wrote:
which makes me doubtful of it uses satellite access for anything accept locating us if we can make a regular cell call for some kind of help.

While the evidence that you have seen might logically make you think differently, the recent "smart" phones actually have a GPS chip in them. The phone/data network is used to get the maps but isn't needed again until you go a LONG way down the road and need a new section of maps. Unlike a "real" GPS, it won't store the entire map of the US, for instance, all at once.

Last summer we rented a houseboat on Lake Cumberland in Kentucky. We were able to use Google Maps to navigate the entire lake, it showed our position in real time as we cruised around. Never missed a beat. Between that and a detailed map we knew where we were at all times.

pnichols wrote:

If what you say is indeed true of how smart phone navigation works, then it sure needs to be explained and talked about way more by smartphone manufacturers and retailers.

That brings up a question - how many of you smartphone navigation users have ever had something like a "no satellite signal" message appear on the screen when trying to navigate out in areas where there also isn't any cell signal available?

A "no satellite signal" message of course should occur in such situations as when a cell phone is inside your RV away from the windows. That message sometimes appears on the screen of my Garmin navigator when it doesn't have line-of-sight satellite access - but I've never seen that kind of message appear on our smartphone ... which makes me doubtful of it uses satellite access for anything accept locating us if we can make a regular cell call for some kind of help.

Smart phone navigation has pretty much always relied on the GPS (sometimes in cooperation with the cell tower triangulation) because the cell tower triangulation is nowhere near as precise in most cases, often insufficient to determine what road you're on exactly. It's the difference between "low-power/low-accuracy" positioning and "high accuracy" positioning on my (Android) phone, if I'm not mistaken.

Google Maps doesn't explicitly say "no GPS signal" or something similar, but it will show the "you are here" blue dot as gray instead of blue util it can get a fix on the location, and shows the estimated error of the fix with a blue circle around it if it's not super precise. I think I remember reading that cell phones can get a GPS fix more rapidly than standalone GPSs when in range of a cell tower because the time and/or satellite information needed is available via the cell tower, rather than having to be decoded from the GPS signals. Of course, if you're out of cell phone range, it will take longer for the phone to get its first location fix via GPS, similar to a normal GPS. (There are variations in speed there depending on the sophistication of the GPS chipset, too.)