12th May 2005

Marine GPS

GPS changed the face of marine travel and exploration forever by offering unparalleled simplicity and ease for the mariner, while combining it with the power and complexity required for any voyage. Not just for the commercial or large-scale captain, GPS offers advantages for every ship and every purpose. We’ll look at GPS solutions for the recreational mariner.

Two main types of unit are available for marine GPS:

Fixed GPS/Marine Chartplotter

This GPS solution attaches to the ship and gets it power from it. An antenna is placed in a suitable location – usually outside or above deck – and the GPS unit itself is affixed to a surface within the bridge or cockpit. Sometimes the antenna is an internal unit, meaning that the system overall has a smaller footprint.

Using maps which are either in-built or downloadable, coastlines, sea depths, routes, waypoints and distances are all easily displayed. Navigation is made easy with waypoints and courses programmed and saved into the unit for easy access.

Some GPS systems come with a sounder for accurate reading of the depth of the sea; fishing aids are also available to sound out for fish below the surface.

Basic Marine GPS/Handheld GPS

These come in both mapping and non-mapping versions, and can often double up as a car GPS, due to their compatibility with street maps. While they offer less unique marine functionality than a fixed system or a Chartplotter, they can still be useful for navigation purposes.

What can it do?

Versatility is order of the day when at sea, and most GPS systems do not disappoint:


The number one feature, particularly for a hand-held GPS system, is how well it’ll stand up to punishment. All sea-going GPS systems are waterproof, most are very sunlight-resistant, and shock resistant.


Some more expensive models offer a sounding facility. Sounding the depth to determine a good anchoring or fishing location is an invaluable maritime tool: using GPS to do this saves time and energy and gives very reliable results.

WAAS compliance

WAAS is a technology which works to enhance the accuracy of regular GPS navigation, both on land and at sea. Using the Wide Area Augmentation System, accuracy is increased to pinpoint your location to within 3 metres of your actual location: close enough for any purpose. Right now, this technology is only available in North America, but it may be worth investing in, should Europe catch on to the trend.

Colour Screen/High Contrast Display

For night or daytime, you need to be able to see where you’re going. Ensure the monitor display is adequate.


Not all marine GPS units offer mapping; most ones over ?150 will. When looking at map functions, consider the storage levels (how many maps can you keep?) how far in you can zoom, the availability of maps relevant to your location etc.

Sailing Aids

Some GPS systems offer alarms when dangerous circumstances occur, e.g. a dangerous stretch of water is upcoming, or the anchor’s being dragged.

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