GPS satellites circle the Earth twice a day in a precise
orbit. Each satellite transmits a unique signal and
orbital parameters that allow GPS devices to decode
and compute the precise location of the satellite.
GPS receivers use this information and trilateration
to calculate a user's exact location. Essentially,
the GPS receiver measures the distance to each
satellite by the amount of time it takes to receive
a transmitted signal. With distance measurements
from a few more satellites, the receiver can determine
a user's position and display it electronically to measure
your running route, or anywhere.