Global Positioning System or, GPS, satellites are stationary in their relation to the earth's position. Your GPS receiver uses the satellite signals to determine your position.
GPS antennas are mushroom-shaped. Your antenna should be installed with an unobstructed view of the sky, away from magnetic fields.
Latitude and Longitude
Lines of latitude run east to west around the earth. These imaginary circular lines run at a right angle to the north and south poles. Lines of longitude run from the north to south pole. Because the earth is a sphere, lines of longitude are farthest apart at the equator, and closest at the poles. Latitude and longitude together form a grid pattern that is used to determine your global position.
Degrees, Minutes and Seconds
Distance along lines of latitude and longitude is traditionally expressed as degrees, minutes and seconds. Each degree contains sixty minutes, and each minute contains sixty seconds. In an effort to make GPS more user-friendly, manufacturers commonly express locations as degrees, minutes and decimal minutes. A minute of latitude is equal to roughly 1.1 miles. Sailors commonly refer to a mile a minute when talking about navigation.
GPS systems enable users to save locations, or waypoints, in the memory of the unit. These waypoints are given names, and can be used for future navigation. GPS systems can calculate the distance between waypoints, giving the operator valuable information about travel time and fuel consumption.
GPS units make navigating simple, and can be used to plan out the most direct course to your favorite fishing hole. By using GPS, mariners take the shortest route to their destination, saving time and fuel.