Geographic Frontiers


It’s Academic

Everyone a Sensor

In a recently published paper in Science Advances, researchers examined the possibility of using crowdsourced cell phone GPS data to provide early warning of earthquakes. Indications are that it could work. With miniaturized sensors, what else might our smart phone potentially detect—air pollution, the extent of climate change. Who would have thought we could save others—and save the planet—by buying a smart phone.

In a sense, armed with our smart phones, each of us has become a sensor (or more accurately a sensor operator). The initial destructive moments of the Nepalese earthquake were captured via smartphone photos and videos and were quickly shared. An individual turned on his cell phone video to capture a foot chase by a South Carolina policeman only to record what by all accounts looks like the unjustified shooting of an unarmed black man by a white officer. It was largely through the analysis of smart phone photos and videos provided to the FBI and the Boston police that the Boston Marathon bombers were identified.

Now there is a new dimension to the smart phone as a sensor. Crowdsourced smart phones potentially could provide early warning of earthquakes.

Results of a study recently published in the journal,
Science Advances, showed that the Global Positioning System (GPS) sensor in smart phones is sufficiently sensitive to detect movement caused by earthquakes of magnitude 7 or greater.

While the GPS sensors are not nearly as sensitive as the GPS sensors used in existing ground-based earthquake detection networks, there is strength in numbers. Their research showed that if over 100 smart phones were similarly triggered, sufficient data was created to characterize the earthquake event. A sufficiently large number also ensured that phones jostled around through normal use weren’t being inadvertently interpreted as signaling an earthquake. A sufficient number also can account for phones not receiving a strong GPS signal. When one thinks about it, 100 smart phones is a fairly small number—perhaps just two tenths of a percent of the smart phone users in an area.

While the concept shows promise, there are some “details” that would need to be worked out.

Data from cell phone GPS sensors would need to be rapidly transmitted to a processor that could assess when an earthquake event has begun and then transmit that information the broader set of cell phone users who could potentially be affected. When all this is done in a matter of seconds—prior to the really damaging earthquake waves arriving—warning recipients may have just enough time to get under their desk, get out of an elevator, or pull their car to the side of the road. (We have to remember that currently, early warning for earthquakes is measured in seconds—not minutes or hours.)

Smart phone vendors would need to agree to make some software changes to their operating systems, and users would have to agree to share their locational data. This later aspect may be a tough one for some users who think too much of their data already is being collected by those who claim to have nothing but good intentions.

The authors of the study are quick to admit that the smart phone network—at least the way smart phones are currently configured—are not as accurate as the early warning earthquake detection networks installed in high threat areas such as southern California. However, they believe it would be relatively cheap to implement and a reasonably accurate alternative for the many regions around the world that don’t have the sophisticated ground-base early warning networks.

But let’s not stop here.

How about air pollution? As far back as 2009, a NASA scientist created a nanosensor-based chemical sensor the size of a postage stamp that could be plugged into a cell phone. The device could detect low concentrations of airborne ammonia, chlorine gas and methane. Enough people with chemical sensors attached to or imbedded in their smart phones could provide more accurate air quality assessments. As the crowdsourced data is relayed to a processing facility, a more accurate picture the extent of air pollution could be obtained. Running the data against existing models could show how the pollution might spread and the extent of the area for which warning must be issued.

How about climate change? With a reduction in the number of weather stations, some—but by no means all—believe we can’t as accurately assess the extent of climate change. Could crowdsourcing be the answer? Cell phones with imbedded thermometers could transmit temperature information from their location. More temperature data from more locations might give better picture of the extent of climate change. While presumably not as accurate as established weather stations, there could be strength in numbers. The larger number of readings could be statistically adjusted to correct for variations in the accuracy of the cell phone sensors.

The applications may not pan out under the rigor of scientific analysis. They do however illustrate how sensor networks may change in just a few short years. Information we can collect via our cell phones could change radically.

We usually think of crowdsourcing as an active function. Someone asks for some help, and the crowd—or at least the portion of the crowd that is so inclined—responds. When everyone is a sensor, crowdsourcing also becomes a passive activity. You simply agree to share and leave our phones on. Who would have thought that by having a smart phone we’d be helping others know when an earthquake is coming? Perhaps we’ll help others know where harmful air pollution is and even help assess the extent of climate change. Buy a smart phone, save the planet.


The Science Advances article was published on 10 April 2015. The authors are: Sarah E. Minson, Benjamin A. Brooks, Craig L. Glennie, Jessica R. Murray, John O. Langbein, Susan E. Owen, Thomas H. Heaton, Robert A. Iannucci, Darren L. Hauser. They are affiliated with the United States Geological Survey, the California Institute of Technology, the Jet Propulsion Laboratory, the University of Houston, and Carnegie Mellon University. They tested their hypothesis against a hypothetical magnitude 7 earthquake based on the characteristics of the Hayward Fault in Southern California and against data from the magnitude 9, 2011 Tohoku-Oki earthquake in Japan.

A 10 April 2015 National Geographic article, “How Your Phone Could Save You From an Impending Earthquake” by Michael D. Lemonick was also helpful. It summarized the research paper and also described the difference between P and S seismic waves. The P waves precede the damaging S waves. In detecting the P waves, the cell phone warning may occur in a sufficiently short time that warning would get out before the S waves arrive.

The following information about the NASA Ames scientist developing a cell phone chemical sensor was dated 20 October 2009 and was found at:

Jing Li, a physical scientist at NASA's Ames Research Center, Moffett Field, Calif., along with other researchers working under the Cell-All program in the Department of Homeland Security’s Science and Technology Directorate, developed a proof of concept of new technology that would bring compact, low-cost, low-power, high-speed nanosensor-based chemical sensing capabilities to cell phones. The device Li developed is about the size of a postage stamp and is designed to be plugged in to a mobile device to collect, process and transmit sensor data. The new device is able to detect and identify low concentrations of airborne ammonia, chlorine gas and methane. The device senses chemicals in the air using a "sample jet" and a multiple-channel silicon-based sensing chip, which consists of 16 nanosensors, and sends detection data to another phone or a computer via telephone communication network or Wi-Fi.

See this web site for a balance discussion on the reliability of surface temperature readings as they relate to climate change.

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