tracking someone by cell phone in an emergency

"Michael"

- you ring the number and ask whomever answers.

.... Phil

In an ideal world, yes, that would do it. This person is suicidal however, and does not want to be found. It's a sad situation.

If it makes any difference, this is in Ohio, United States.

Any way to track the phone using triangulation, etc.? Has to be a way.

Thanks,

Michael

On a sunny day (Tue, 16 Aug 2011 01:42:33 -0700 (PDT)) it happened Michael wrote in :

Hack a heart rate monitor, add a siren. So when the person dies the siren will go, and they will find him / her.

Michael schrieb:

Hello,

it is possible to find the position of a cell phone, but the cell phone must be activated and the phone company must cooperate. The cell phone should be in a position where it may be received by three different net transmitter stations. By measuring the delay between the net transmitter station and the cell phone answer you get a distance, with three such distances you get a position. This is done in Europe in emergency situations, but there are some legal restrictions. I don't know if this is legal in Ohio and if the phone companies have the necessary equipment for delay measurement. If the cell phone is in a position where only one or two transmitter stations may receive it, triangulation is not possible, you only get a circle or two possible positions where the cell phone should be.

Bye

It doesn't actually need the delay timing measurement to get a rough fix. There are heuristics to do it based on signal strength and provided the signal is reaching 3 or more base stations they do OK. Obviously it is not as precise but it is a lot better than nothing if the emergency caller really does not know where they are!

A sideline is that overflying stealth aircraft can be detected by the effect they have on the mobile phone network bit error rate.

That is still a useful constraint on searching for someone who is lost on the moors but has their phone. There are a few places where there is literally no signal on certain networks and then you are stuck.

Regards, Martin Brown

"Michael" "Phil Allison" "Michael"

In an ideal world, yes, that would do it. This person is suicidal however, and does not want to be found.

My god you are one, pathetic jerk.

... Phil

Why shouldn't we respect his/her decision ?

Signal strength is more or less useless in the mobile environment. A mobile station in an unfavorable spot e.g. cellar would have a weak signal (=far away).

The GSM system is used in Europe and apparently in some parts of the US. It is a time division (TDMA) system with 8 time slots. The handset must be able to adjust the response burst timing so that it arrives to the base station ain the middle of the time slot (thus limiting the range to 35 km, even if the RF field is OK).

For this reason, each GSM base station knows the distance to the handset with some accuracy (blurred by local reflections etc.). Thus, with even a single base station, the radius from the base station is known and looking at maps, possible and impossible locations can be accepted/rejected.

While the distance measurement is inherent in the GSM TDMA system, at least CDMA based systems should be able to measure the distance to the base station, if properly equipped. After all, the GPS system uses CDMA for distance measurement.

snipped-for-privacy@downunder.com

- and that is a serious crime.

.... Phil

In which parts of the world ?

There are (2) methods that cell phone companies use to triangulate the location of a handset during a 911 call. With a court order, they can also track most types of phones even if they are not engaged in conversation, since the handset is always registered with the network.

Method 1 is used for handsets that have GPS capability. If they have a clear view of the sky, or otherwise have a fix on the location, they simply transmit the GPS coordinates to the carrier (network).

Method 2 is something called Time Distance of Arrival (TDOA). Essentially, this methods traingulates the location using several nearby towers. If there are enough towers, the location fix can be pretty good. Research a company called TruePosition

A method you can use, that is expensive, time-consuming, and not guaranteed to work, is to try to triangulate the signal yourself. To do that, the phone must be broadcasting. Also, in your triangulation efforts, you would undoubtedly come across every other handset transmitting in the vicinity. A spectrum analyzer & suitable antenna operable at cellular/PCS frequencies is not cheap. A Rhode & Schwarz PR-100 portable receiver runs about $20,000, but is a fine instrument for such a task.

I assume the suicidal person in question here is a relative or close friend. My only comment there is "that sucks", and realistically, there's only so much you can do. Rather than spend resources trying to hunt cell phones, I would look into other ways to help this person out. Traking their cell phone wihtout the assistance of their network provider is most likely going to be a non-starter of an idea.

-mpm

Up to 10 years in jail for the crime in NSW, for example.

.... Phil

Ok, thanks to everyone who gave helpful replies. I received an email this morning that her friend was able to reach her phone and talk some sense into her, which is good.

Thanks again for the technical insight.

Michael

According to Wikipedia, assisting a suicide is a crime in Australia, Canada, China, New Zealand, the United Kingdom, and to a lesser or partial degree in many other countries. In most states in the U.S. it is illegal; there are limited exceptions for physician-assisted suicide in a few states.

All of these (I believe) are restrictions on actively assisting a suicide. I'm not aware of any jurisdictions in which a person would face criminal prosecution for failing to take action to prevent a suicide.

"Dave Platt"

... Phil

You'd have to have access to the routers in the towers and substations - call the victim, and triangulate which towers are closest to his location.

Or call NCIS and ask for Tim McGee or Abby Schutto.

Good Luck! Rich

So offer him the Darwin award.

Suicide is the sincerest form of self-criticism. Throw a little chlorine in the gene pool!

Good Luck! Rich

Gratuitous cruelty, not funny and not pretty.

The OP claims to have been dealing with a real situation where someone's life was at stake. On Usenet, who knows, but it might well have been real.

Phil Hobbs

How old are you Rich? Pretty poor form.