01 June 2003
No wine before its time
West Coast vineyards sense and process temperatures for best harvest.
Berkeley Wireless Embedded Systems is pushing its networked sensor regime, which leverages recent and ongoing innovations in radio frequency communication technology and microelectromechanical systems.
Tiny operating system (TinyOS) is a component-based run-time environment designed to provide support for deeply embedded systems, which require concurrency intensive operations while constrained by minimal hardware resources.
The technology originally worked in and for the Smart Dust hardware platform, and its scheduler fits in fewer than 200 bytes of program memory (today.cs.berkeley.edu/tos).
Wired magazine reported the operating system's circumstances from a vineyard in Canada where it's webbing a structure of temperature sensors called motes.
Intel Research and Agriculture and Agri-Food Canada (AAFC)—Canada's version of the U.S. Department of Agriculture—are using this wireless sensor network to measure air temperatures across a 50-acre expanse in southern British Columbia.
Working on a hillside overlooking Lake Okanagan in British Columbia, the owners of King Family Farms will use the temperature sensors to help protect their crops from frost damage.
After analyzing long-term data from the sensors, they'll also be able to harvest grapes more productively and cut their use of pesticides and fungicides.
Each palm-sized mote consists of a sensor board, a radio processor, and two AA batteries. Hanging from trellises as close as 20 feet apart, the motes form an efficient, low-power wireless network that connects to a PC in the vineyard manager's office.
Radio signals hop from one mote to the next until they reach the manager's PC. The software running on the network's open-source operating system, TinyOS, selects the best transmission routes for the motes to use.
"The shortest physical distances or the fewest hops don't always make the best paths," said Anind Dey, senior researcher at the Intel Research Lab (www.intel-research.net/berkeley) at the University of California at Berkeley. "We've developed algorithms that instead determine which paths will have the least signal loss, for example."
Scientists at the UC Berkeley lab designed the motes, which are also working at a vineyard in Dundee, Ore., and a wildlife habitat on Great Duck Island in Maine. Crossbow Technology (www.xbow.com) out of San Jose, Calif., sells commercial versions of the same motes.
The temperature motes will help King Family Farms target specific plants for frost-control measures, such as misting the plants with water.
"Water here is a community resource that is becoming increasingly scarce," said Don King, who co-owns the vineyard with his brother, Rod. "The system will help us avoid over watering."
The motes will also help King get a better night's rest. Until now, he's been fighting frost the old-fashioned way: by patrolling the vineyard at night with a lantern and a portable thermometer.
Even very small farms have numerous hot and cold spots, which require different amounts of water. "Cold air runs down a hillside like a river," said Pat Bowen, a plant pathologist for AAFC, Canada's agriculture department.
Parts of a farm's topography can hold on to cold air longer than other parts, causing pockets of frost damage that affect vines' productivity for years.
But cold isn't always bad for grapes. Arctic blasts from the Canadian Northwest produce grapes with a sweeter, more concentrated juice, which winemakers use to produce icewine, one of King Family Farms' specialties.
Cumulative temperature data from the motes will tell King which plants will yield the best icewine. It will also help King choose the best moment to pick his grapes—a process known as precision harvesting. A plant's total number of high- and low-temperature days determines whether its fruit will make a better Pinot Noir, Chardonnay, or other wine.
"At best, viticulturists have used average temperatures over broad areas to make that calculation," said Intel researcher Richard Beckwith. "This makes those numbers much more accurate."
The scientists at King Family Farms hope to add additional motes that measure light, humidity, and other factors that affect plant growth and disease resistance.
AAFC's Pat Bowen wants to use the data to map the farm's tiny subclimates, called mesoclimates. The map will depict planting zones similar to those shown in seed catalogs, "but on a much smaller and much more precise scale," Bowen said.
Don King, meanwhile, said he is excited about what the motes will tell him about his land. But he is still waiting for them to build software that allows him to view and crunch the data on his PC. IT
Nicholas Sheble writes and edits the Sensors and Technology Advances department. Write him at nsheble@isa.org.
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