XPost: misc.news.internet.discuss   
   From: here@is.invalid   
      
   Air Force souring on GPS?   
      
   According to a recent report in Popular Mechanics magazine, the U.S   
   Air Force, the military service that manages GPS, is looking into the   
   possibility of navigating aircraft and missiles using the Earth's   
   magnetic field. Vehicles would make use of detailed maps of the field   
   to determine position and guidance. The Air Force is investigating   
   such a navigation system due to the vulnerabilities of GPS. In a   
   conflict, an enemy might destroy the satellites in orbit or jam or   
   spoof GPS signals.   
      
   The full details of how such a magnetic system would work are not   
   given but the concept of using the geomagnetic field not just for   
   direction, as is done with magnetic compasses, but also for   
   positioning goes back to ideas promoted by British Astronomer Royal   
   Sir Edmund Halley (of comet fame). Halley believed the earth's   
   magnetic variation could be tied to longitude. Halley undertook   
   several voyages in the North and South Atlantic measuring geomagnetism   
   and in 1701 produced a map that showed areas of like magnetic   
   variation. He connected these areas and invented the isogonic line.   
   Halley's attempt to devise an isogonic-based system for fixing   
   longitude never worked, however, and the later invention of the marine   
   chronometer by John Harrison put the concept to rest.   
      
      
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)