The South Dakota woman's pickup truck was embedded in a snowdrift during a recent blizzard. Using her cellular phone, Karen Nelson called 911-but emergency personnel could not pinpoint her location until they scrambled a National Guard F16 and asked her to tell them when she heard the jet fly overhead.
"That was enormously expensive and not practical for every 911 call for which a location is needed," said Dr. Alan Rogers, associate director of the MIT Haystack Observatory, who helped develop a system for tracing cellular phone calls economically and less dramatically.
Working with the Associated Group Inc., of Bala Cynwyd, PA, Haystack scientists adapted radio astronomy and geodesy techniques they had developed for the National Science Foundation and NASA to the cellular phone project. In addition to Dr. Rogers, Professor Charles C. Counselman of the Department of Earth, Atmospheric and Planetary Sciences, Haystack engineer Joel Goodman and technician Dave Fields worked on the project.
"This is a spinoff from our basic research to a practical application that benefits society," said Joseph Salah, director of Haystack.
The Technology Licensing Office matched up Haystack and Associated two years ago. Working together, they developed the TruePosition wireless location system. Haystack created the radio location algorithms and signal processing codes.
Last Wednesday, the state of New Jersey launched a 90-day test run of the system on the southern portion of the New Jersey Turnpike. New Jersey Attorney General Peter Verniero and Federal Communications Commission Chairman Reed Hundt received the first call, placed by a state trooper from his cruiser at an unspecified location. The point of origin was immediately located.
New Jersey state police report that 23 percent of 911 calls are made from cellular phones, with the number of calls doubling every year since 1992. Nationwide, the Cellular Telecommunications Industry Association reports that 50,000 calls to 911 are made daily from cellular phones.
The impetus to develop call-tracing technology came from an FCC order requiring cellular phone companies to install tracking equipment within five years that is accurate within 125 meters.
While other systems are being developed, an advantage of the True-Position system is that it uses existing antennas and cellular phones. Tests using prototypes of the TruePosition system in Baltimore and Philadelphia have demonstrated an accuracy of about one-tenth of a mile.
"There is still much work to be done to ensure accuracy and reliability in all environments-especially in areas like Manhattan, where multiple propagation paths severely limit the accuracy," Dr. Rogers said. "But the competing technology of putting a [Global Positioning System] receiver in the cellular phone, which will work as long as there is a clear view of several satellites, will fail completely in the 'canyons' of large cities, or inside buildings. We're likely to be busy for a few more years."
Associated Group has renewed the MIT contract through 1997 and is sponsoring the Berkman Postdoctoral Fellowship in radio astronomy at Haystack, named for Associated's CEO, Myles P. Berkman.
Mr. Hundt, Mr. Verniero and State Police Superintendent Carl A. Williams were enthusiastic about the demonstration on the New Jersey Turnpike. Louis A. Stilp, vice president of the Associated affiliate involved in the cellular project, conducted that test as well as an earlier one in Houston.
"Expectations are high as we begin the 90-day test of the system along the New Jersey Turnpike," Dr. Rogers said.
A version of this article appeared in MIT Tech Talk on January 29, 1997.