Almost two years ago I wrote about how the Civil Air Patrol uses cell phone forensics to find people lost in the wild, a process that is much more complicated than TV shows would make you believe. (You can read that column here)
This complexity means that if you make a call then hang up and make another call without moving, different towers may be involved with each, which seems to indicate that you’re in two different locations. In an urban area with lots of towers, a single call can appear to originate from dozens of places.
As a result, using what is called network-based location to find a phone can be very misleading. A little online searching finds plenty of stories about arrests or convictions based on what turned out later to be a misinterpretation of network information.
Even in areas with few towers, like the North Country, things can get tricky. Because cell phone signals are mostly line of sight, the tower nearest to you may be blocked by trees or hills, and your signal may end up being picked up by a more distant tower.
The CAP’s Cellular Forensics Team has compiled detailed maps of each tower’s coverage area, which because of geography isn’t always a nice clean circle. They say they’re the only organization that has such maps readily available. They also gather tower information about how far away the phone was; azimuth and beam-width information about the tower’s three antennas, which point in different directions; and knowledge about how accurate different cell phone companies are in the information they provide.
I mention this because the national CAP just announced that they’ve made their 1,000th find using cell phone forensics. This is from the release:
Civil Air Patrol, the official auxiliary of the U.S. Air Force, conducts approximately 90% of all search operations within the United States as assigned by the Air Force Rescue Coordination Center (AFRCC). Before 2009, the AFRCC assigned about 2,000 missions a year to CAP, with searches for activated aircraft emergency locator transmitters dominating. In February 2009, the satellite system that monitored the old style 121.5-megahertz emergency beacons was turned off, and the annual mission count was reduced by at least half.
Since then, the cell phone team has contributed to a dramatic rise in the number of saved lives credited to CAP by the AFRCC. In fiscal 2018, CAP was credited with a modern record of 155 lives saved in a single year. Most of those saves — 147, or 95% — occurred with the support of the cell phone team.
If you want to know more, check this presentation given by the Cellular Forensics Team a few years ago. That team has been involved in 1,500 search and rescues throughout the country, including a number in New Hampshire. It’s at vimeo.com/220654137.