IEEE Spectrum tests a sensor-laden smartphone that maps where GPS can’t
By YU-TZU CHIU / NOVEMBER 2012
Photo: Bill Chen
NAVIGATION
KUNG-FU: Our reporter finds her way
around the Museum of Contemporary Art, in Taipei, using a prototype smartphone
that can navigate without GPS.
21 November 2012—At no point did the kung-fu masters in Ang
Lee’s film Crouching Tiger, Hidden Dragon need a navigation system to locate
targets. As a kung-fu film fan with a bad sense of direction, however, I was
happy to have an experimental new indoor
navigation system
guide me through the exhibition “King Hu: The Renaissance Man,” at the Museum of Contemporary Art in Taipei last August. ( Hu’s 1971 film, A Touch of Zen,
was one of the inspirations for Crouching
Tiger, Hidden Dragon.)
As anyone who’s ever been lost
in a multistory shopping center or parking garage knows,GPS doesn’t work indoors. So Internet
giants like Google, telecom operators, and smartphone makers are working on
indoor navigation.
I came to the Hu exhibition to
try out a version of indoor navigation that calculates your position by a form
of inertial sensing, or dead reckoning—reconstructing your position from
acceleration and orientation. At the entrance, where GPS signals vanished to
almost none, I was given a Google Nexus One smartphone that had been modified
by engineers from STMicroelectronics and CSR. The phone’s software displayed my location
on a map of the ground floor. As I moved, the app displayed my route and showed
me as a little cartoon-person icon, whose motions simultaneously mimicked mine
as I walked, rested, and even climbed stairs.
The modified smartphone
contained an STMicroelectronics-CSR indoor navigation module, a combination of
CSR’s navigation software, SiRFusion,
and an STMicroelectronics MEMS chip that featured accelerometers, gyroscopes, a
compass, and a pressure sensor. Sam Sun, a CSR field-applications engineering
manager, opened the back of the smartphone to show me the module and its
smaller-than-a-square-centimeter MEMS chip. They fit into the Nexus One in a
space that was freed up by replacing the original battery with a smaller one.
When I finished climbing the
stairs and stepped onto the second floor, the smartphone showed me a new map.
Even if a GPS signal had been available, figuring out what floor I was on
would’ve been a challenge. GPS is only one-third as accurate in the vertical
direction as it is in the horizontal—too fuzzy to tell one floor from another.
The key here was the pressure sensor—the only type of sensor the modified Nexus
One contained that you don’t commonly find in today’s portables. Although we
can’t feel the decrease in air pressure from one floor to another, several
companies have developed sensors that can. “So if you go to a skyscraper
offering location-based services, say, the Taipei 101 building, the device can
tell you which floor you’re actually on by measuring levels of the air
pressure,” says Robert Yu, an STMicroelectronics senior technical marketing and
application manager.
The software was customized with
information on the museum’s show. Whenever I approached an object, its icon
would pop up on the display, which I could click on to hear a description of
it. The experience was much better than using a headset listening device to
follow a self-guided audio tour, because I didn’t have to spend seconds
matching the object’s number with the audio segment.
“What if two icons are shown at
the same time, partly overlapped?” I asked CSR’s Sun, when we approached an
object that was just dozens of centimeters away from another.“How do I know
which is which?”
“Don’t forget, you still have
eyes,” he replied, adding that the navigation system could be switched to
manual mode if users preferred retrieving the information for specific targets.
So even without a well-trained
kung-fu master’s sense of direction, I could still easily navigate the museum’s
collection of King Hu’s kung-fu films.
For more advances in indoor
navigation, see “Navigating
the Great Indoors,” IEEE Spectrum, November 2012.
