Data Hacking

Glossary
12-channel A GPS receiver that can keep a lock on 12 satellites
simultaneously.
14-channel A GPS receiver that can keep a lock on 14 satellites
simultaneously.
Accuracy A measure of how close the position given by the GPS is to the
true position.
Acquisition time The time it takes for the GPS receiver to determine its
initial position.
Active antenna An antenna that amplifies the GPS signal before feeding
it to the GPS receiver.
Active leg The segment of a route that is currently being traveled.
Almanac A data file that contains orbit information on the GPS satellites,
clock corrections, and atmospheric delay information. The almanac is transmitted
by the GPS satellites to a GPS receiver to enable it to keep a lock and
reacquire a lost signal quickly.
Atomic clock A very accurate clock that uses the decay of elements such
as cesium or rubidium to measure the passage of time. A typical cesium
clock has an error of about one second per million years. GPS satellites
make use of multiple atomic clocks.
Availability The number of hours that a particular location has sufficient
satellites to allow a GPS receiver to work.
Breadcrumb trail A visual representation of a path taken, shown on a
map. Also known as a track.
C/A-code Short for “Coarse/Acquisition” or “S-code,” a name given to
the civilian GPS signal.
COG See Course over ground.
Cold start The power-on sequence in which the GPS receiver downloads
almanac data before establishing a fix.
Constellation The set of GPS satellites in orbit around the Earth.
Control segment The Earth-based component of the GPS network
(the satellite control system).