Backtrack: A function that allows you to retrace the route you traveled if you stored waypoints as you went along.
Bearing: Your direction of travel between two points, measured in degrees relative to true or magnetic north. Bearing ranges from 0 to 360 degrees.
Coordinates: A set of letters (indicating direction) and numbers (indicating latitude and longitude) that describe a position on the surface of the Earth.
Course Over Ground (COG): The direction in which the GPS receiver has been taken.
Cross-Track Error (XTE): Sometimes called the "course deviation indicator," this number represents the amount of perpendicular distance you have wandered from your programmed route.
GoTo: A basic function of any GPS unit, GoTo directs you to a chosen waypoint or destination, usually by showing on the unit's display an arrow that points in the direction the user is to go.
Route: A course of travel linking two or more waypoints selected by the user.
Speed Over Ground (SOG): The speed at which the user of a GPS receiver is traveling.
Universal Transverse Mercator: An alternative coordinate system that divides the Earth's surface into a flat grid of 60 zones, each zone 6 degrees wide, instead of using the traditional longitude/latitude system. UTM currently is used mostly by "serious" navigators and cartographers, but it's becoming more common because, once learned, it's simple to use.
Velocity Made Good: A numerical value that shows the rate at which the user of a GPS receiver is nearing a destination waypoint.
Waypoint: Also called a landmark, a waypoint is a precise position on the Earth identified by a set of coordinates. All GPS receivers let you name waypoints, and many allow you to label them with icons for landmarks such as campsites and overlooks, and then link multiple waypoints to create a route. GPS units typically store at least 500 waypoints.