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Thursday, April 2, 2009

Cellphones And SAR

Before joining SAR, I was pretty much a fuddy-duddy about cell phones in the backcountry. To me, that was a place to be free from all electronic gadgets (yes, I even had a "thing" about GPS's, believe it or not) ... but especially phones. Besides, I figured they wouldn't work out there most of the time anyway.

Well, since becoming a SAR volunteer, I admit I've changed my mind--not that I condone yacking on the phone while walking a trail--and learned a thing or two about the value cell phones can have, both to the backcountry user who gets into a jam and to Search & Rescue. I've now been involved with a number of missions where cell phones have literally saved lives and/or made it much easier for our team to narrow the search area or even pinpoint a subject's location.

Speaking of pinpointing one's location, I recently read a brief article entitled, "Cell Phone Users Beware: 911 Operators May Not Be Able To Locate You." Till then, I'd been under the impression that all cell phones that have a GPS chip built into them--meaning all phones made within the past two years--would enable 9-1-1 to obtain a caller's exact coordinates (or at least determine the location to within a small area), just by the person dialing in to the call center. As the article points out, however, this is the case only in areas that have "enhanced 9-1-1 systems."

The Federal Communication Commission's website states:

"The FCC's wireless Enhanced 9-1-1 (E9-1-1) rules seek to improve the effectiveness and reliability of wireless 9-1-1 services by providing 9-1-1 dispatchers with additional information on wireless 9-1-1 calls."

This additional information includes the phone number of the wireless caller, the location of the cell site or base station transmitting the call, and the latitude and longitude of the caller to within 30 to 300 feet. This is accomplished by using either some form of radiolocation from the cellular network, or by using a Global Positioning System receiver built into the phone. How a 9-1-1 caller would be located depends on which service provider and the type of phone being used. Though the federal government requires wireless companies to comply with Enhanced 9-1-1 rules, cellphone users do need to check with their service providers or phone manufacturers to get details about their phone.

Here's an interesting article, discussing how a cell phone signal was used to locate the family of James Kim, who disappeared in Oregon during a Thanksgiving road trip. In "Turning Cell Phones Into Lifelines," writer Marguerite Reardon explains:

"Mobile devices, when they are within range, constantly let cell towers and the mobile switching center, which is connected to multiple towers, know of their location. The mobile switching center uses the location information to ensure that incoming calls and messages are routed to the tower nearest to the user.

If a subscriber is unable to get service, this location information is usually purged from the mobile switching center. But some location information may remain in call detail records. Some mobile operators may store the most recent communication between a device and a mobile switching center for a certain period of time, usually 24 hours.

When someone is missing, even this small bit of information can prove useful in determining the approximate location of a device using the updates from the mobile switching center."

There are some interesting comments following the article as well as links to related stories. Read more....

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