Sunday, March 18, 2012

911 Fail: Your phone’s GPS may not locate you

GPS cellphone errorI’ve posted tons of links over the years about how cellphone GPS has helped rescue folks in the wilderness. Of course you have to be where there is reception to reach 911. But as many GPS users know, the urban environment has its own challenges in terms of accuracy.

Knowing all this, I was still pretty shocked to see a story showing the results of a Michigan TV station’s test of cellphone GPS accuracy and how well it helps (or doesn’t help) 911 responders.

Now granted, they tried from challenging locations like a parking deck, but even less difficult environments proved problematic. Consider these results from a facility that appears to be pretty open

Or, from a corner table at Kelly’s Restaurant in Cedar Springs.

"This one showed you, like, 14951 White Creek Avenue NE, which is a day-care center," a Kent County dispatcher said when answering a Target 8 test call from Kelly’s.

That was the T-Mobile 4g Android MyTouch, and that day-care is more than a mile-and-a-half away.

Then, there was the At&T iPhone again — this time off by more than four-and-a-half miles.

AT&T officials, when told about Target 8’s results, asked for specifics, including the make and model of the phone, its operating system and when the call was made. After receiving that information, they refused to discuss the test results.

"I cannot provide any insight on the GPS testing," AT&T spokesman Jermaine Spight wrote in an email to Target 8. "We found no issues with our services during the time your test was conducted. AT&T fully complies with all applicable federal regulations regarding wireless E911 service."

Unfortunately they failed to say which version of the iPhone this was. Want to test it yourself? Don’t call 911, but simply fire up your phone’s map application. Does it match your current location?

My own results were interesting. I’m currently in Michigan visiting my wife’s family. I tested my phone in a basement room, below grade, with no windows and using GPS Test got a 200’ error that quickly dropped to less than 40’. Moving back upstairs next to a large bay window, Google Maps showed my location pretty much spot on, on my Motorola Droid (OG), which you can see in the image above. But see the other “person” on the map? That’s my wife’s current location, shown using Google Latitude. The problem is that her Droid X was in the basement, not the mile away it showed on the map. Feel free to share your own results below. Here’s the video version of the news story BTW…

Does the GPS on your cell phone work?:

About Rich Owings

Rich is the owner, editor and chief bottle-washer for GPS Tracklog. Connect with him on Twitter, Facebook or Google Plus.


  1. So when GPS satellite lock doesn’t work because of obstacles like roofs, a cell phone uses Wi-Fi or cell tower positioning, which are less accurate. How is this news? I’m guessing the 911 operator will still ask the person their location, just like was done before E911. How often is a person indoors and unable to tell the operator their location?

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