Basic Definitions - Garmin GPS 90 Owner's Manual & Reference

The GPS 90 is a powerful navigation tool that can guide you anywhere in
the world. To better understand its operation and capabilities, it may be help-
ful to review the basic terms and concepts briefly explained below.
Navigation is the process of traveling from one place to another and knowing
where you are in relation to your desired course.
Position is an exact, unique location based on a geographic coordinate system.
Most aviation navigation is based on the latitude/longitude coordinate system.
Meridians of longitude are a set of imaginary circles around the earth that pass
through the north and south poles. Longitude describes position in terms of how
many degrees it is east or west of the Prime Meridian (0º longitude).
Parallels of latitude are another set of imaginary circles that are perpendicular
to the earth's polar axis. Latitude describes position in terms of how many
degrees it is north or south of the equator (0º latitude).
A waypoint marks an exact position fix so it can be recalled for future use. The
GPS 90 lets you mark waypoints electronically, without physical landmarks.
Bearing is a compass direction to a particular destination (waypoint) from your
present position.
Track is a compass direction representing your course over ground.
Getting
Started
Basic
Definitions
3