Global Positioning System (GPS)
GPS has been around for many
years and has only recently evolved into a common term. The system
functions by using 24 medium orbit satellites. These satellites orbit the
Earth once a day and travel the same track each time. A GPS receiver will
receive and process the satellite signals. With four signals your location
and elevation can be determined. Output information may consist of
latitude/longitude, elevation, speed, and direction. Many systems will
also plot your location on a map.
GPS was originally designed and
used by the military. It is still controlled by the Department of Defense.
Until March of 2000 the GPS signal was slightly distorted. At that time
the distortion was removed, improving placement. Newer GPS receivers go
one step further, using WAAS will also improve your location plotting versus
actual location. Errors range from a 1-2 feet to several feet and is
dependent on a number of factors. The most common would be number of
satellites and the quality of the signal.
This system has become a vital
tool for storm spotters and chasers. It allows for accurate plotting and
back-tracking after the event. Additionally, some users allow themselves
to be tracked and this information is relayed to monitoring stations. Net
Control or the NWS can monitor spotter location for reports and urgent
situations.
A good source for additional
information:
Colorado University. (Reference for material on
this page.)
Product information may be
found at:
Delorme
Magellan
Garmin
