Global Positioning System
GPS can give your wearable computer position (lattitude/longitude),
time, and altitude information, providing the receiver can "see"
enough of the positioning satellites that orbit the earth. Accuracy
depends on number of satellites "acquired," level of encryption the
military is using at any given time, and if differential GPS is being
used. Cheap (~$300) receivers can be gotten in PCMCIA card or small
boxes with serial interfaces. These systems can be good enough,
depending on conditions, to see the lane changes of a car. For more
information, see below. More recently, Ashtech has announced a system
that integrates the Russian and US systems to get 15m accuracy. See
the Ashtech entry.
Last modified: Tue Nov 28 14:39:15 1995