locating by cell phone
This thread branched from "Death on Canterbury mountain" on . Explore the branch.
" "… Phone polling over the next few hours …." They ring your phone. If it is on & rings they can then pinpoint your GPS location ? I usually turn mine off. Perhaps I should leave it on & crank it down to Airplane Mode or something ? " no the phone needs to transmit for that to work and it won't transmit in airplane mode.
Could be the polling they mean is manual as discussed above or it could just be the automatic location updates that all mobiles do periodically with the network. Police (and thus SAR) can request the records of a subscriber's location updates from the network provider and thus have access to a record of the subscribers movements. Either way, wayno is right: they will know nothing about your location unless you are transmitting, and flight mode turns transmit off.
This is from a question I asked on the "Death on Mt Somers" thread. ""Lim , who was a warden at Woolshed Creek Hut, was reported overdue at 4.30pm on Friday and phone polling over the next few hours indicated the man's phone was at one location."" So, he was answering his phone after the 30m fall, or was it something else ?. If not "flight mode" then de-powering it to something else ?.
> they will know nothing about your location unless you are transmitting That's what I figured, and furthermore there's a difference between a phone calculating its location and broadcasting it, versus a phone company deriving the phone's location from coincidental data it holds. These days if a phone isn't actively determining its own location and transmitting it by some protocol, how accurate can a position be gotten these days merely going from looking at things like signal strength detected from the phone at the cell towers? Would this position have been reasonably accurate, or is it more likely there was just a rough idea and a helicopter zipped over some likely destinations and spotted him?
depends whats measured, simply having a static signal strength and or ping time could be taken to indicate its still, or if it has the direction to the phone . or theres triangulation going on between towers to give a position.
Polling refers to the normal data exchange between terminal (phone) and BSC (base station controller = tower). This data includes the signal strength as measured by the terminal. It could also include rough directional information if the base station (tower) is using sectoring (where multiple directional antennas are being used instead of an omnidirectional one). If the terminal is in range of x base stations, the signal strength of each is enough to : x= 3+ : locate the terminal x= 2 : locate the terminal to two possible positions x= 1 : locate the terminal to a circle (centre = base station) If sectoring is being used (on 1 base station), 2 towers is enough to locate the terminal. In any event, if the received signal strength isn't changing (within limits) then the terminal is stationary.
There might be a few omnidirectional towers out there but the few I've worked on have had 120 degree segments. Which helps narrow things down quire a bit since you know a distance from each tower the phone can reach and which 120 degree segment a phone is in.
Yes, that's sectoring - although the antennas can be programmed to any size segment. Omnidirectional would only be used in unusual circumstances (eg remote, low traffic). You can learn more from metadata than the call data itself - clever little monkeys, arent we?
""... phone polling over the next few hours indicated the man's phone was at one location."" A human was transmitting or the phone was transmitting of it's own accord ?. Crux of it is, would it be a plus to have the phone on if you were struck down & couldn't otherwise communicate ?.
All phones are in continuous contact with surrounding towers, unless fully powered off or in flight mode. Flight mode means "don't poll for base stations". If you are unconscious and the phone is on (and not in flight mode) and in range of a base station and SAR are looking for you THEN it would be useful. Of course, if you're concious then you'd just phone home 😎
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