- The Washington Times - Wednesday, March 9, 2005

An icon tracks computer-science graduate student George Ionkov as he carries a tablet through the A.V. Williams building at the University of Maryland’s College Park campus.

Post-doctoral student Moustafa Youssef watches the dot from a server in Ashok Agrawala’s office.

Mr. Youssef, who is conducting his studies in the Institute for Advanced Computer Studies’ MIND Lab, uses a navigational and positioning system similar to GPS, or Global Positioning System. He and other students helped Mr. Agrawala, a professor in the computer science department and director of the Maryland Information and Network Dynamics (MIND) Lab, develop the system, called Horus.

“Any area you want to keep track of something, you can always use GPS technology, provided you’re willing to accept the limitations the technology places in terms of accuracy,” says Mr. Agrawala, who holds a doctorate in applied mathematics. “GPS cannot give location information indoors or when the view of the sky is restricted.”

Despite its limitations, GPS has a wide range of applications and can be installed in automobiles, cellular phones, personal digital assistants, laptop computers, watches and hand-held devices.

The U.S. Department of Defense began developing GPS in the mid-1970s for military use, opening it up for commercial use in the 1980s. A satellite-based navigation system, it consists of a constellation of 24 satellites that orbit the Earth twice a day at an altitude of 12,000 feet. The satellites continuously broadcast high-frequency radio signals containing precise position and time data back to Earth.

GPS receivers take the data from at least three satellites to calculate the user’s exact location within meters of accuracy. Using a mathematical principle called triangulation, GPS receivers compare the time when a satellite transmits a signal to when it is received and calculate the distance from the satellite to the receiver.

The receiver combines the data from three or more satellites to show the user’s location on a display or electronic maps stored in memory.

Unlike GPS, Horus can work indoors and does not require satellites to transmit information because it is able to use wireless fidelity (Wi-Fi) access points, Mr. Agrawala says. Like GPS, Wi-Fi also uses radio spectrum.

“Horus measures the signal’s strength that it’s getting from the access points in an area and, based on that, determines its location,” Mr. Agrawala says.

Pinpoint, another system Mr. Agrawala has under development, uses portable access points or pinpoint nodes that can be placed at an area lacking Wi-Fi but where tracking is desired. The nodes, as envisioned, will send signals back and forth and to another node placed on the person or object to be tracked, determining location from the distances measured. For example, firefighters will be able to place the nodes around a building fire and on firefighters’ helmets to track where they are in the building.

Alternatively, the typical GPS receiver receives signals from satellites and, because it does not transmit information, cannot be used as a tracking device, says Ted Gartner, spokesman for Garmin International Inc., an Olathe, Kan., designer and manufacturer of navigation equipment.

“It only lets you know where you are,” he says.

GPS receivers installed in an automobile or designed as portable units act as both compass and road map. The receivers can, depending on the unit, provide location; bearing; odometer and speedometer readings; trip distance; distance to destination; estimated time of arrival; turn-by-turn directions; and route directions to restaurants, gas stations and other places listed in locators.

“You can enjoy the ride and pay attention to what’s around you instead of worrying where to make your next turn,” Mr. Garner says about automobile GPS receivers. “We’ve all been lost before. These kind of units make it difficult to do that.”

GPS receivers integrated with transmitters can assist in tracking vehicles and people by transmitting back the signals, such as in locating and tracking a fleet of trucks.

The Prince George’s County Public Schools system, for example, is installing a GPS tracking system by Nextel Communications on the school district’s 1,300 school buses. A built-in cellular phone with GPS capabilities will track the location and speed of each bus, relaying information in real time to the transportation department.

“Nextel’s system lets the schools track where every bus is and where it is going. This means improved safety and efficiency since they will know immediately if there is a problem or a better way of getting somewhere,” says Chris Hackett, vice president of education for Nextel Communications, headquartered in Reston. “That is a pretty important considering those buses are transporting the county’s kids.”

GPS has a host of other applications, such as record keeping; surveying; mapping; forecasting; research; and providing navigational information for driving, boating, flying, hiking and running.

“I like the idea that I can go out and get these precise locations so easily, store them and go in and create a map from scratch,” says Tanya Allison, professor and program coordinator for the Department of Applied Technology at Montgomery College in Rockville. “What used to take us days and months to do now can be done in hours or less.”

The Virginia Cooperative Extension office in Arlington County uses GPS to map different species of invasive plants, a problem for the county that affects all of its parks.

Since last spring, program staff and volunteers have been taking GPS readings of patches of plant species under study. They draw out the data on Mylar, or clear plastic, placed on top of an existing map and take the information to the Geographic Information System (GIS) department to be digitized into a new map.

“It helps us look at the scope of the problem and see how widespread the species are in different parks. It helps us plan better,” says Jan Ferrigan, invasive plant program coordinator for the Arlington County Extension office.

Other metro-area extension offices, including Fairfax County’s, use GPS for tree registration and animal and livestock identification. Livestock are given an identification number to track their locations and to help identify and prevent the spread of infectious and contagious diseases.

“Before, it was just county records in logs and directories,” says Adria Bordas, horticulture extension agent for Fairfax County.

Copyright © 2018 The Washington Times, LLC. Click here for reprint permission.

The Washington Times Comment Policy

The Washington Times welcomes your comments on Spot.im, our third-party provider. Please read our Comment Policy before commenting.


Click to Read More and View Comments

Click to Hide