What They Do
The Global Positioning System (GPS) is a satellite-based navigation system that provides
accurate position fixes 24 hours a day on land, sea and air, in all weather conditions, and without
a subscription or user fees. They're a great tool for boaters because the system incorporates 24
satellites that provide navigational data to GPS units. That means they can provide directions to
your destination and help you find your way if you're lost. The system has prompted the biggest
revolution in navigation since the magnetic compass, and the revolution shows no signs of slowing
down.
What You Need to Know
Handheld, mountable or fixed-mount? Those three options depend on the type of boat you own
and the kind of boating you're doing. For small boats, a handheld GPS unit is ideal. Handhelds are
pocket-sized, tend to be reasonably priced (some are under $100) and make a great primary
navigational tool (though it's always good to have charts on board).
Larger
mountables (also called portables) incorporate some features of handheld and fixed-mount units.
They work well on mid-sized center consoles and small cruisers. Their larger displays offer easier
visibility in rougher water than handhelds. They're powered by either batteries or the boat's 12V
system and can be removed to prevent theft.
Large boats with significantly larger helm console space will typically use a fixed-mount receiver with larger, high-resolution displays. Ergonomically, the fixed-mount units are top-of-the-line. These units can be linked to secondary displays in the cockpit or on a flybridge. Fixed-mount units are powered by the boat's 12V DC power and typically use an external antenna for enhanced reception.
At this level, most GPS units can be linked as a system with other functions like radar, sonar and VHF. Fixed-mount receivers with detailed charts, known as chartplotters, can either be used as stand-alone units or linked with other electronic functions. Connected to a transducer, they can display underwater information using a split screen or superimposed display fishfinder format.
Most
GPS units come with a "base map." These maps offer different levels of detail, depending on the
unit and manufacturer. The higher-end receivers use electronic moving maps that show your position
superimposed directly on the chart in order to give the best detail. The detailed maps can be
preloaded on the receiver, via CD-ROM downloads, postage-sized cartridges or the Internet. Some
units are also sold as crossover models that incorporate automobile navigation technology with
waterproof features. Others offer enhanced visuals like aerial photographs of harbors.
Three years ago, GPS accuracy was in the range of 6 to 12 meters (20 to 40 feet). With the
proliferation of the WAAS (Wide Area Augmentation System) program, the accuracy is now 3 meters
(just less than 10 feet). Most GPS units are WAAS-enabled.
The Final Word
Once the size of a duffle-bag and the cost of a small fortune, GPS units are now so compact,
intuitive and affordable, it's hard to justify not owning one if you boat anywhere other than a
small lake or river. Even then, it's a great tool to have for boating at night.