A Global Positioning System (GPS) has become one of the de facto must have electronic marine devices for every boat on the water. A marine GPS device provides two functions in particular that, once you get used to, you will wonder how you ever managed without.
First, marine GPS provides you essential information about where you are and how fast you are traveling. Most marine GPS units will tell you where you are within two to three meters of accuracy, how fast you are traveling and how far you are from shore.
Second, most marine GPS units allow you to set waypoints. A waypoint is a marker for where you are currently. This feature allows you to plot a navigation route through craggy rocks or difficult waters, avoiding buoys, nets and other obstacles. Multiple waypoints form a route that you can save and use as a guide for the inbound journey or re-use another time for safer and easier navigation to a favorite location. Another great benefit of setting waypoints is that you can mark significant finds whether this is an abundant fishing spot, a great scuba diving location or the position of a wreck.
By overlaying GPS waypoints with an integrated mapping tool or chart plotter, a marine GPS can give you a very precise picture of where you have been, where you are, where you want to go and what lies in your path.
Ultra-precise GPS marine electronics include the addition of signals from the Wide Area Augmentation System (WAAS). WAAS is program that was developed the Federal Aviation Administration to correct GPS errors. Satellites travel on an elliptical path in orbit around the earth. The calculations used to determine where you are depend also on knowing exactly where the GPS satellites are. The orbital path of a satellite is disrupted by a score of natural phenomena, including space weather, the gravitational pull from the Earth and other factors. WAAS performs corrections for these factors, increasing the accuracy of the GPS signals that your GPS receiver processes.
If your marine GPS is WAAS enabled (and most are these days) then you will benefit from this improved accuracy without doing a thing. You dont have to configure it or subscribe to it. However, it is only available in North America; so if you are sailing outside the US waters just know that the accuracy of your marine GPS may dip from better than three to less than seven meters and possibly to less than fifteen meters. WAAS is a good feature to look for when shopping for discount marine GPS.
WAAS enabled marine GPS can be mounted (fixed position) or portable (hand-held) systems. Hand-helds are useful if you leave the boat to visit a local hotspot on dry land, explore an island or simply find where you left your boat in a large and unfamiliar marina. If you do intend to use your portable marine GPS on dry land, then it is definitely worth paying more for one that comes with built-in maps because following a compass point that is plotted as a straight line is not easy on land, especially in urban areas or over mountainous terrain.