Today's technology brings the modern mariner with a variety of marine electronics to choose from, and many of the latest marine devices come fully integrated with GPS-capable electronics. GPS does more than help you navigate to your destination. One of the most powerful features of GPS is that it allows you track where you have been and get back there safely. It also allows you to set waypoints for significant finds along the way. You can set a waypoint for a tricky piece of land that juts out below water (and then avoid it) or mark the spot of a detected wreck, a beautiful coral reef or a great fishing spot.
Much like sonar technology, which bounces sound waves off objects below the surface of the water, marine GPS devices use high-frequency low-power radio signals emitted from satellites in orbit around the Earth to determine your position on the water. When these signals hit your GPS receiver, the receiver calculates an xy coordinate setting your position. Combine the accuracy of your marine GPS with other marine electronics capabilities, such as a fish finder or a chart plotter and you have a powerful tool to aid you in your quest for the best fish, exploring deep sea wrecks, or simply trying to navigate a rocky coastline on a Sunday afternoon.
An automated GPS overlays the xy coordinates of a vehicle on the maps of the United States and other countries. This is how it knows exactly where you are and can guide you to another location. Marine GPS electronics use various contour maps of lakes, rivers and oceans. These marine maps are collectively the result of our human exploration and partly derived from satellite imagery.
While GPS is an automated technology, the maps change as we learn more about the ocean bottom, so maps can be updated with new information. The newer your marine GPS device, the more accurate your marine map. You may also be able to upload newer maps to your old marine electronics; it's a feature to look for when you make a purchase. For example, if a new wreck is found that was not previously known, it gets added to the ocean maps.
One popular set of maps known as BlueChart incorporates high resolution satellite imagery of below waters with aerial photography of coast lines and coastal roads for superior navigation both on the water and around the coastline. BlueChart G2 Vision is an optional plug-in for some marine GPS devices and provides 3D views above and below the water line.
Also, look for marine GPS devices that use CANet to connect to other similarly equipped GPS devices so you can stay in touch with other boats in the area. CANet lets you share maps, waypoints and other information. If you have a fleet of boats, for example, this technology can greatly improve your productivity. Simply transmit coordinates of the best fishing areas.