Even smart phones have their limits, but developers are finding ways to build sophisticated sensors than can connect to phones and expand mobile networks.
Third of four parts.
When there’s seemingly an app for everything, you could get the idea that smart phones are capable of anything. But even as they find new, sophisticated uses as part of environmental monitoring, situational awareness and other mobile networks, developers are struggling with certain limitations in smart-phone technology.
One obvious shortcoming in many areas is the uneven availability of cellular signals.
“For military applications, that is the biggest limitation right now,” said Akos Ledeczi, associate professor of computer engineering at Vanderbilt University, whose team has been developing a smart-phone app that locates snipers for the Defense Advanced Research Projects Agency. “They need to build up the infrastructure and it needs to be secure, jamming-resistant and all that stuff.”
On the civilian side, more accurate Global Positioning System signals and synchronization of phones are at the top of the wish list, said Jules White, Virginia Tech professor of electrical and computer engineering.
“Right now, on phones, the timing information is inaccurate. By the time you get the time from GPS to the operating system and Java, the timing is completely inaccurate,” White said. “There are many, many milliseconds of error. If phones could provide precise timing information from GPS up to the application layer, that would be useful for many of these applications.”
Finally, despite having GPS receivers, accelerometers, cameras and audio receivers, the sensors in phones are limited. This is partly because manufacturers don’t see a market advantage in building in a sensor that, say, measures ozone levels. But it’s also because some sensors currently require too much power or cannot be reduced to cell-phone size.
“Air pollution sensors are electrochemical sensors, and they use a whole lot of power, so you can't put them in the phone,” White explained. “And if you have some kind of external device you'll either need a large battery or it will only work for a few hours. That's definitely a problem.”
Developers are responding to the current limitations in two ways — by building custom sensor devices that include smart-phone capabilities and by designing sensor devices that plug into phones.
The first option was the choice of Chris Thompson and his colleagues at SplitSecnd. Thompson had worked with White at Vanderbilt to develop a smart-phone application called WreckWatch that would use a smart phone’s accelerometer to detect when an accident had occurred and alert an emergency response center. When they moved to commercialize the system, Thompson said, they encountered several issues with the cell phone platform.
“A lot of cell phones don't have the same security, don't have the same development model, and so forth,” Thompson said. “With the iPhone, for example, you really can't have an application that runs constantly in the background. Also, we didn't want to limit our customers to have to have a certain smart phone. We found the best way to do that was to just build our own hardware.”
Other developers have moved to create sensor devices that plug into phones to take advantage of their capabilities. Sensorcon Inc., for example, is taking advance orders for Sensordrone, a keychain-size device that can measure levels of various gases, temperature, humidity, air pressure, infrared temperature and light – all for under $200. Like most external sensor devices, Sensordrone connects to users’ phones via Bluetooth.
One thing that has researchers, activists and some in government excited is the potential that smart-phone sensor networks offer for community involvement in many types of data collection.
“I think there's potential,” said Richard Wayland, director of the Environmental Protection Agency’s Air Quality Assessment Division. “I don't think a lot of them are quite ready for prime time yet but it won't be long before many of these [smart-phone sensor networks] are further enhanced. And they don't necessarily have to be as good as the regulatory monitors.”
They could, for instance, be used in a screening mode to alert to a potential problem. “Then if you find something with the screening mode, you can bring in more sophisticated monitors to do more in-depth analysis,” Wayland said.
According to Tim Dye, senior vice president at Sonoma Technologies, a California-based consulting firm that is working with EPA on its AirNow efforts to collect and make available air-quality data, “the quality of the sensors is not where we want it to be, but that’s changing pretty rapidly.”
He points to AirCasting, a platform for recording, mapping and sharing health and environmental data using smart phones that was developed by HabitatMap, a non-profit environmental health justice organization. The platform includes an Android application that receives and processes data collected by various sensors, including the AirCasting Air Monitor, an under-$200 device that can measure temperature, humidity, carbon monoxide and nitrogen dioxide.
Each AirCasting session can capture real-world measurements, annotate the data to tell the story, and share it via CrowdMap. “Once it’s on the phone you can start logging the data and share it through the website,” Dye said. “And on the website you can crowd source information.”
The West Oakland Environmental Indicators Project (WOEIP), a resident-led, community-based environmental organization, is collecting air quality data using a handheld device designed by researchers at the University of California-Berkeley and Intel that includes a cell phone circuit, GPS receiver and sensors that measure particulates.
According to Brian Beveridge, co-director of WOEIP, a custom device was required because particulate sensors are still too large to imbed in smart phones, though he says engineers at Berkeley are working to miniaturize a particulate sensor.
“Smart phones are becoming the tool of preference because they have well-integrated GPS and they have a variety of other components built in that can be multi-purposed,” Beveridge said. “And you can plug other sensors into the jack on most phones.”
Whether it’s a smart phone or a handheld device that has cellular capabilities, Beveridge is excited by the potential of more portable and affordable sensing devices to put monitoring capabilities in the hands of communities. “I think the most powerful thing we’re doing is teaching community residents to do data gathering, to understand the power of data, the weaknesses of data, and to better understand what science means,” he said.
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