What is a GPS?
Hand Held GPS UnitMany maps, such as road maps, only deal with the two-dimensional location of an object without taking into account its elevation. While convenient, these maps do not accurately represent the surface of the earth. The earth is contorted (“relief”), and because of this latitude, longitude and elevation are necessary to locate areas exactly on a map (three-points, or “triangulation” is required to accurately locate something within 3-Dimensional space). Maps that deal with three dimensions are called topographic maps. Topographic maps take into account the elevation of the area being mapped above a reference datum , thus showing the actual shape of the area. Photographs, satellite imagery, surface and subsurface scientific exploration and other means of gathering data have changed the way modern maps are constructed.
The Global Positioning System (GPS) is a satellite based navigational system. The GPS Receiver (often simply called a GPS) is a device that receives signals from up to seven satellites and does some intricate mathematical computations to determine your position, which it then displays on a screen. A basic model can be had for as little as $ 200. Gadget freaks (like me!) can pick up fancy units with colour chart reproductions for $ 1,500 and more. It’s important to stress that all electronics are subject to failure, usually at the most akward possible time. You should be sure you’re aware of your position through manual methods such as dead reckoning, viewing the shore (coastal cruising) or a sextant (offshore), so that if your fancy GPS fails, you can still find a way to your destination. If you’re still fairly dependant on the fancy electronics, it’s a good idea to have a GPS that runs on batteries and is thus not dependant on internal boat power, so that if you have electrical proble
