GPS devices may not be all that accurate

  • Article by: KATIE HUMPHREY , Star Tribune
  • Updated: July 27, 2013 - 6:58 AM

Garmin GPS.

Photo: Chris O'Meara, Associated Press

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Karla Sand knew the theater was in south Minneapolis, she even had the address. She just didn’t know how to get there. Neither did the GPS unit in her Toyota Corolla.

Faced with a road blocked by construction, the electronic voice kept urging her in circles — until she missed the play.

“I knew it was wrong obviously, but I kept thinking, ‘I’m going to try again. Maybe if I try here it will reroute me,’ ” said Sand, 43, of Andover.

Turns out the digital era hasn’t saved the directionally challenged. Despite high-tech GPS devices, we still get lost. It’s difficult to quantify how often, but evidence of users’ frustration is easy to find. Misguided victims vent on Facebook, YouTube, message boards and with memes poking fun at obvious GPS failures. When Apple’s iOS Maps app debuted riddled with errors, social media went berserk.

Max Donath, director of the University of Minnesota’s Intelligent Transportation Systems Institute, has devised his own solution: “I carry four or five GPS apps on my phone. I switch from one to the other if one of them gives me grief.”

Our reliance on smartphones and in-car GPS units has become so widespread that only about half of Americans still carry paper maps in their cars.

Yet sometimes the technology itself gets turned around: Road construction confuses outdated map databases, satellite signals get blocked, and suggested routes may not be the most direct. And then there’s user error.

“It’s amazing how that happens,” said Lyuba Ellingson, 27, of Minnetonka, who confesses to having gotten lost, even with digital help. “I can’t always blame it on GPS, but sometimes it’s very justified.”

Misdirected technology

There are plenty of reasons why GPS gets gummed up.

For starters, the great orange obstacle of summer — road construction — is a roadblock to many mapping programs.

The digital maps, especially those made for GPS devices in vehicles, are developed long before the detour signs go up. To make matters worse, it typically takes months of verification before an update is issued, said Donath, who also is a professor of mechanical engineering at the U. That sometimes means maps are outdated before they are even issued.

“If there’s been any construction, for example, or if a road changed from two-way to one-way, that will definitely send you off into never-never land,” Donath said.

He battled that scenario in Duluth last year when trying to get to a meeting amid a sea of detours unknown to his GPS app. “It kept putting me on a road that didn’t exist,” Donath said.

Even if the roadways are correct, outdated address databases can mislead. And there are other obstacles: Tall buildings, or even trees, can prevent satellites from accurately triangulating a driver’s position. And the routes calculated by a device might technically be the fastest or most direct, but not the easiest to follow. Some mapping apps, including Google Maps and Apple’s Maps, are more dynamic than in-vehicle GPS systems because they’re constantly updating based on information collected from users. But there are still mistakes.

“It’s not so simple building these maps,” Donath said. “There are a lot of complexities, and getting them right can be difficult — even for Google.”

Digital map dependent

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