July 25, 2011 By Sarah Rich
York County, Pa., plans to verify the locations of more than 200 cell phone towers to ensure that 911 calls placed from mobile devices are accurately tracked.
Communications Director Carl Lindquist said the county depends on the locations as they’re provided by cell phone companies. Calls from older mobile phones that don’t have built-in GPS must be triangulated from the location of cell towers in order to determine where a caller dialing 911 is. The caller’s location is estimated based on where the call signal is pinging off a tower.
“When we go to try and trace that call, if we’ve got bad information, it negatively impairs us to figure out where you are,” said Lindquist, “because our computer records are going to show you’re within 300 meters of this area, when really because the tower is in a different location, you’re actually 300 meters [from a different location].”
County commissioners approved $84,000 — funded through the county’s wireless fund — to precisely locate each of the 200 cell phone providers’ towers in the county. Lindquist said York County was double-checking the tower locations as a matter of “due diligence.”
Newer cell phones and smartphones contain GPS technology, which can directly report a 911 caller’s location to a public safety answering point, he said. But occasionally the GPS coordinates still aren’t provided by the cell phone company, in which case first responders are forced to rely on the location of the cell phone towers to conduct the tracing.
For older cell phones that don’t have integrated GPS, cell phone towers help pinpoint the caller’s coordinates. The location data from cell towers can usually get emergency responders within 300 meters of the caller. But if the cell tower’s location is inaccurate, first responders might have a hard time finding a 911 caller.
GIS technology is integrated into York County’s computer-aided dispatch. The system includes all locations of the cell phone towers that are provided by the cell phone companies.
The county has contracted L.R. Kimball, a firm specializing in communications technology, to survey the cell tower locations. When all the locations are double-checked, a second GIS layer will be added to York County’s computer-aided dispatch with the updated geolocation data as needed.
Several years ago the county implemented a new digital radio system. At that time, L.R. Kimball helped the county test its ability to locate calls made from smartphones and newer cell phones.
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