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Network-Based Tracking Gives Law Enforcement Alternative to GPS

Technology allows law enforcement officials — without carrying handheld devices or bulky hardware — to pinpoint an individual’s position within 150 feet using data from cell towers.

by / April 29, 2011

Individuals in the midst of committing a crime better leave their mobile devices at home, as law enforcement personnel are tracking cell signals more accurately.

Assisted Global Position Satellite system tracking (A-GPS) has been around for more than a decade and used effectively by police and government entities to keep tabs on potential suspects. But network-based tracking, which uses signals from cell towers, is steadily improving and quickly moving to the forefront in surveillance operations.

Unlike A-GPS, which some cell phone users can recognize and stop by tampering with the GPS chip in their device, network-based tracking using cell towers can’t be detected by cellular users.

“The feedback I get from law enforcement agencies said that GPS doesn’t solve the problems they have,” said Marty Feuerstein, chief technology officer of Polaris Wireless. “A lot of [officers] tell me that it’s easy for users to disable GPS, you can jam it [and] there are battery life implications.”

One network-based tracking software package is Polaris Wireless’ Wireless Location Signatures (WLS) technology. The program is allowing police and other officials — without carrying handheld devices or bulky hardware — to pinpoint an individual or group’s position within 50 meters using data from cell towers.

As a mobile device registers signal strengths and delay times from other cell phones, the devices report that data back to a base station. The WLS software, which is housed on a computer server specified by the agency using the program, takes the compiled information and correlates it against a radio environment map using a pattern-matching algorithm, giving the approximate location of whoever is holding the cell phone.

GPS tracking is still useful however, according to Jeff Kagan, a telecommunications industry analyst. He said both network-based and GPS systems perform well, although their usage should depend on the situation.

“For GPS, you need to see the sky, whereas with wireless you don’t,” Kagan said. “But GPS can get you very, very close. Which one is better? I don’t really think we can say, but ultimately, law enforcement should have both.”

The accuracy of network-based tracking is dependent upon cell tower density, so while the software can be effective in suburban and rural areas, urban locations are where the best results are seen. Feuerstein admitted that WLS technology does better indoors, but in suburban locations, it can pick up a cell phone location within about 100 meters on average.

Kagan said that reason was exactly why GPS remains popular.

“You still have to triangulate between cell towers,” Kagan said, referring to network-based tracking. “The more towers you have, the more accurate it will be.”

If better results are wanted — particularly in nonurban environments with long distances between cell towers — beacons, antennae and small portable base stations called femtocells can be deployed to enhance location results.

The WLS technology can also be used to set up a “geo-fence,” where anyone with a mobile device approaching a monitored area would be immediately picked up and registered on a computer screen.

While surveillance operations typically require warrants before tracking suspects, the ability to track without detection is a useful tool during investigations, giving law enforcement a head start on observing and apprehending a potential criminal.

“If someone was walking around and entered the [target] zone, the geo-fence would turn red, flash and [the program] puts an alarm on the screen,” Feuerstein said.

When asked about cost, particularly as it relates to state and local law enforcement agencies, Feuerstein said it depends on the purchased software package.

Vertical Tracking on the Horizon

Today’s network-based tracking technology is horizontally based — capable of identifying targets in a specific area. But what is missing is an ability to determine how high in a building a person is. But that capacity is coming, according to Feuerstein.

His company has been working on technology that returns location results within a few floors, depending on the situation.

“In general, we can get within five floors,” Feuerstein said, regarding the vertical tracking technology under development. “It’s hard to get down to floor-level reliability. It’s one thing to do location if you are on the ground or the first few floors. But it’s much more of a challenge if you are in a penthouse of a 50-story building.”

The program that offers vertical pinpointing is currently undergoing testing and although Feuerstein wouldn’t reveal a release date or formal name to the software, he indicated that it would be released by the end of 2011.

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Brian Heaton

Brian Heaton was a writer for Government Technology magazine from 2011 to mid-2015.

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