Canadian Coast Guard
www.ccg-gcc.gc.ca
Common menu bar links
Differential Global Positioning System (DGPS)
GPS / DGPS Made Easy
Definitions
Navigation: The process of traveling from one place to another and knowing where you are in relation to your desired course.
Differential GPS (DGPS): An extension of the GPS system that uses land based radio beacons to transmit position corrections to GPS receivers.
Ground speed: The velocity you are traveling relative to a ground position. The speed that you are traveling over the bottom.
Position: An exact, unique location based on a geographic coordinate system.
Waypoint: A specific location saved in the receiver's memory that is used along a planned route.
Bearing: The compass direction from your position to a destination.
Latitude: A north / south measurement of position perpendicular to the earth's polar axis.
Longitude: An east / west measurement of position in relation to the Prime Meridian, an imaginary circle that passes through the north and south poles.
Multipath error: Errors caused by the interference of a signal that has reached the receiver antenna by 2 or more different paths. Usually caused by one path being bounced or reflected.
Track: The direction of movement relative to a ground position.
Desired track: The compass course between the "from" and "to" waypoints.
Crosstrack error: The distance you are off a desired course in either direction.
2D navigation: At least three satellites with good geometry have been locked onto and a 2-dimensional position fix (latitude and longitude) is being calculated. "2D Diff" will appear when you are receiving DGPS corrections in 2D fix.
3D navigation: At least four satellites with good geometry have been locked onto and your position is now being calculated in latitude, longitude and altitude. "3D Diff" will appear when you are receiving DGPS corrections in 3D mode.
Porr coverage: The receiver is no longer tracking enough satellites for a 2D or 3D fix.
