PRA_fix

[John Young]

   8-4-95. NYPaper:


   "A Contract Is Awarded To Improve Navigation."

      The Federal Aviation Administration yesterday awarded a
      contract to greatly improve a navigation system that
      would let civilians pinpoint their locations anywhere in
      the United States to within 21 feet.

      The augmentation would consist of 36 receiving stations
      in the United States, each fixed in a precisely surveyed
      spot. Each station would listen electronically for the
      signals given off by the halo of satellites, and
      calculate what the satellites were saying about the
      station's location. But the station, bolted down, would
      not rely on the satellites to determine its location; it
      would already know that precisely.

      The central office, listening to all 36 stations, would
      establish a correction factor. It would radio the
      correction factor to a different satellite, one in
      geosynchronous orbit over the United States, meaning
      that its position did not change relative to the earth's
      surface.

      The geosynchronous satellite would radio a correction
      factor back to planes in flight, or any other user. The
      plane would also receive signals from the G.P.S.
      satellites, calculate a position, apply the correction
      factor and fix its location.


   PRA_fix