4 ms·
Getting coordinates from towers doesn't work the way most people think it does. First, there are still many many areas in the US where your phone will only be
by thaumaturgy 6y ago
Getting coordinates from towers doesn't work the way most people think it does.
First, there are still many many areas in the US where your phone will only be able to get a reliable signal to one tower, and those areas also happen to correlate well with areas that people like to go for outdoor recreation.
Second, you have to have somebody involved that knows the right specific questions to ask, and you have to have a representative at the phone company that's not a fleshy automaton. Search and rescue efforts tend to be coordinated by local law enforcement (usually sheriffs or park services), and training varies a lot. So, for practical purposes, this information is often not available.
Third, the information you get back requires some interpretation. It's not like the phone company sends back a map with a nice circle on it; you get some values back from one or more radios at one or more locations (possibly with or without orientations for the radios, and possibly that information is current and reliable or not). Then you have to plot those values, and then you have to take into account fun little quirks of physics, like the part where canyons of some kinds of rock can bounce a signal really well and cause somebody to be closer to the tower than the data would suggest. Other formations act like big reflectors.
Zero of the searches that I have been on have included helpful information from cell towers.
- userbinator 6y agoI think all smartphones have a real GPS receiver, which means cell signal is not necessary at all to get location information; just a view of the sky, which is likely to be the case if you're lost outside.
- katbyte 6y agoTree cover and valleys as well as phone placement or orientation can have a massive effect on gps signal
- jonah 6y agoVery true, but on a search like this, narrowing a location down to even a couple miles GREATLY reduces the search area.
- tomc1985 6y agoThey use 'assisted GPS', which requires cell service for a reliable reading
- WillPostForFood 6y agoAssisted GPS just helps with a faster initial acquisition. You can put your phone in airplane mode to test it out. It might be a little slower to acquire, but you'll get good accuracy.
- ce4 6y agoThat is not true, A-GPS just speeds up the time to fix by supplying ephemeral data via a sidechannel. It just takes longer to receive via GPS if it is out of date or you have moved position considerately since last fix
- flatline 6y agoI have relied on gps with downloaded topo maps in areas where there is literally no cell reception. iPhone X using AllTrails fwiw, I feel like it must have a real gps radio packed in there somewhere.
- jonah 6y agoIndeed it does have a true GPS satelite receiver. Actually, the iPhones are quite accurate. The iPhone 12 utilizes the GLONASS, Galileo, QZSS, and BeiDou constellations. Utilizing more satellites means determining location more quickly and returns better accuracy especially in marginal environments.
- johnwalkr 6y agoHave you ever used Garmin back in the day, or a USB GPS receiver? It can take a minute or so to get enough initial information to deduce a location at a low datarate. AGPS gets some or all of that information (I'm not sure) from another source, usually a cell phone network so that first location is deduced much faster. Modern phones have GPS receivers, but use AGPS. If a modern phone has no network signal, it will still get a GPS signal, it will just take longer to get the first location. Not to be confused with other technologies such as skyhook [2], which was used in iPhone 1 and other older devices to fuse radio signal strength, known wifi hotspot locations, etc as a kind of pseudo-GPS. It was only relevant for a few years. Wikipedia [1] has a nice short explanation. [1] https://en.wikipedia.org/wiki/Assisted_GNSS https://en.wikipedia.org/wiki/Assisted_GNSS [2] https://en.wikipedia.org/wiki/Skyhook_Wireless https://en.wikipedia.org/wiki/Skyhook_Wireless