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Global Positioning System Selective Availability (SA)


May 1 — The U.S. government will stop intentionally downgrading Global Positioning System data at midnight tonight, according to a White House announcement. The satellite-based system, which was originally designed for military purposes, had become much more valuable as a civilian high- tech tool in electronic devices like on-board car navigation. The increased positioning accuracy will enable a host of newlocation-based gadgets and make current devices 10 times more accurate than they are today.

HOBBYISTS AND HIGH-TECH firms had been lobbying for access to the full satellite data for some time, but until today, the U.S. government was worried about foreign military groups using the system for their advantage. New technologies allow the system to be turned off in specific areas, allowing the U.S. government to allow the more accurate data to flow into civilian areas. Currently, the U.S. employees technique called Selective Availability (SA) to globally degrade the civilian GPS signal. New technologies demonstrated by the military enable the U.S. to degrade the GPS signal on a regional basis. GPS users worldwide would not be affected by regional, security-motivated, GPS degradations, and businesses reliant on GPS could continue to operate at peak efficiency. “It’s rare that someone can press a button and make something you already own worth more, but that’s exactly what’s happening today,” President Bill Clinton said in a statement. “As of midnight tonight, all the people who’ve bought GPS receivers for boats, cars, or recreation will find that they are ten times more accurate.” GPS is expected to be big business. According to the White House, there are already more than 4 million GPS users world wide, and the market for GPS applications is expected to double in the next three years, from $8 billion to over $16 billion. The technology can also be used to enhance other services with location-specific information. Cell phones, for example, can be outfitted with GPS capabilities that instantly make 9-1-1 calls more effective.

Other examples of what enhanced GPS services will mean to consumers, according to the White House: Car Navigation: Previously, a GPS-based car navigation could give the location of the vehicle to within a hundred meters. This was a problem, for example, in areas where multiple highways run in parallel, because the degraded signal made it difficult to determine which one the car was Terminating SA will eliminate such problems, leading to greater consumer confidence in the technology and higher adoption rates. Hiking, Camping, and Hunting: GPS is already popular among outdoor enthusiasts, but the degraded accuracy has not allowed them to precisely pin-point their location or the location of items (such as game) left behind for later recovery. With 20 meter accuracy or better, hikers, campers, and hunters should be able to navigate their way through unmarked wilderness terrain with increased confidence and safety. Moreover, users will find that the accuracy of GPS exceeds the resolution of U.S. Geological Survey topographical quad maps. Boating and Fishing: Recreational boaters will enjoy safer, more accurate navigation around sandbars, rocks, and other obstacles. Anglers will be able to more precisely locate their favorite spot on a lake or river. Lobsterers will be able to find and recover their traps more quickly and efficiently. Increased Adoption of GPS Time:  In addition to more accurate position information, the accuracy of the time data  broadcast by GPS will improve to within 40 billionths of a second.

Such precision may encourage adoption of GPS as a preferred means of acquiring Universal Coordinated Time (UTC) and for synchronizing everything from electrical power grids and cellular phone towers to telecommunications networks and the Internet. For example, with higher precision timing, a company can stream more data through a fiber optic cable by tightening the space between data packets. Using GPS to accomplish this is far less costly than maintaining private atomic clock equipment.


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