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Indoor Navigation Takes Signals And Sensors

Indoor navigation on mobile devices goes beyond GPS to rely on a variety of wireless signals and built-in sensors.

3 min read
Indoor Navigation Takes Signals And Sensors

Indoor navigation. You’re going to be hearing a lot about it over the coming months. Apple, having recently dumped Google’s mapping technology from its mobile devices, will be trying to beat Google at the mapping game. Google will fight back with more and more features, many likely intended for use indoors. (I expect to see some mapping demos at the upcoming iPhone 5 introduction later this week.)

Meanwhile, a number of major mobile device makers and cell phone service providers have teamed up to develop a standard for indoor navigation. Google and Apple are not part of this standardization effort.

Indoor navigation technology is going to be a lot different from its outdoor counterpart. Outdoors, navigation relies, for the most part, on GPS, which can be accurate to within about five meters. Indoors, thanks to attenuation and scattering, GPS falls apart. So good luck getting a usable signal. And even outdoors, GPS is vertically challenged; it's about one-third as accurate in pinpointing your elevation as it is in telling where you are in the x and y dimensions. In other words, even if you do get a signal inside, it's unlikely that GPS will have any idea whether you’re trying to navigate the first, second, or third floor of your local shopping mall.

So indoor navigation, while relying on GPS to identify your general location (at the mall, at the airport), needs some other technology to get you around. Google’s My Location technology in its Maps for Mobile product uses cell phone tower identification when GPS is not available. Though cell phone tower triangulation offers some help indoors, it's not very precise.  So increasingly, indoor navigation systems such as My Location are supplementing GPS signals with information from Wi-Fi hotspots. It will, however, take time to gather this data on available Wi-Fi signals, both protected and open, mapping venues with information about the comparative strength of the different signals at different points. Some approaches propose adding locator beams that use Bluetooth, WiMax, or other radio standards; approach one of these beams and your navigation system can update or correct its understanding of your location.

Still, even with all those radio signals, knowing exactly outside which store a mobile phone user is standing in a crowded mall is tricky, so developers are starting to

incorporate information from sensors within the phone, like pressure sensors that provide altitude, gyroscopes that determine if the user is turning and in which direction, and accelerometers that count steps.

Benedetto Vigna, vice president and general manager of the analog MEMS and sensors group at ST Microelectronics, says that the sensor plus radio approach, in which you “basically trust the sensors in the system, and once in a while check in with a wireless signal” is the way to go, because it reduces power consumption compared with an approach that relies on constant radio signal access. Mike Stanley, a systems engineer at Freescale Semiconductor, agrees. It may not seem like much, he says, but “powering up a radio once a second instead of constantly stretches battery life. (They would say this, of course, given that both companies sell sensors, but they make a strong argument.)

While this sounds like a lot of technology to throw at the indoor navigation problem, the good news is that most of today's smartphones already come fully loaded with much of the necessary hardware. The Samsung Galaxy S3, Vigna says, has all the aforementioned sensors, and most other phones are just missing the pressure sensors. So, for the most part, it’s just a question of getting the software to the phones, and collecting additional navigation data, like the location of Wi-Fi hotspots, from indoor venues. Of course, it would help if the systems were standardized, so folks with iPhones could go to the same malls as folks with Androids.

But while real standardization is not likely to happen anytime soon, indoor navigation is indeed happening now. “I had expected a boom in 2013 or 2014,” says Stanley, “but it is happening already.”

Follow me on Twitter @TeklaPerry.

Photos: ST Microelectronics

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