GPS Receiver Antenna

GPS Antenna and GPS Usage

GPS antenna placement significantly affects GPS operations. Ideally the antenna must be located with a clear view directly upwards. Of 12 orbiting satellites in the hemisphere, a GPS needs only to lock onto 3 (2D fix) or 4 (3D fix) of them. The farther away they are, the more atmospheric and weather interference takes place. Satellites located close to the horizon will be farther away presenting potentially higher levels of signal interference. This is why an external GPS receiver antenna with a clear upward and sideways view is generally preferred. An internal GPS receiver antenna will likely be placed in a cockpit or obstructed location.

Most GPS devices will pin point your position anywhere in the world within 50 feet. A clear view to the sky is best. Moisture and humidity and atmospheric conditions will interfere with antenna signals to some degree and we have very little control over such conditions. Metal obstructions (roof) or dense objects will interfere with signals. Because we have control over placement of the GPS antenna we want to minimize as many interfering objects as possible. Unless your fishing area does not experience conditions like fog, mist, rain, poor visibility, or darkness, a handheld or mounted GPS (Global Positioning System) is “must have” safety equipment to have on board a boat.

A GPS has the benefit of putting a boat close to a fishing spot of known coordinates. It can also help to navigate channels very well using already known safe GPS coordinates, providing the capability is installed of course.

30 satellites orbit the earth at a distance of about 10,000 miles twice per day. Equipped with atomic clocks they send out timing and position signals at the top of every second. GPS units receive these signals using an antenna and calculate time and position using an on-board processor. Latitude and longitude can be calculated with a fix on three satellites known as a 2D fix. Additionally, altitude can be calculated with four satellites known as a 3D fix. (GPS units have the ability to output a precise pulse per second, based on atomic clock time with a 3D fix, a feature not really necessary for maritime navigation.)

As electronic devices, GPS units can break and fail and cannot be entirely relied upon for absolute safety. Offshore boating enthusiasts in particular should be self reliant in their abilities to plot a course using coastal navigation techniques with chart and compass.

It may not be a regulatory requirement to carry GPS, but it makes a lot of sense to do so in the event that something unexpected happens. Some boaters will carry a handheld GPS as a backup unit.

A boat can easily breakdown over the horizon and beyond sight of land. In this situation, wind and currents will carry a small boat miles away from the original breakdown point. If the boater can communicate his GPS position to the coastguard, or even another vessel, the chances of being found (quickly) dramatically increase.

In many localities, fog can materialize and visibility can deteriorate very quickly within five or ten minutes! A GPS may prevent experienced boaters from disorientation and guide them on their correct course whether it is along a channel, or between jetties or heads. (If lost in fog, it is often best to stay put, outside of shipping lanes of course).

If another boat gets into trouble, it sure is nice to have the necessary equipment to report the problem and position right away.

Some side notes here:
A cell phone is not considered a reliable mode of maritime communications. Even if a connection is made, the coastguard may be too far away to help, where as boats in the immediate vicinity will hear a VHF broadcast and may be in a better position to render immediate assistance.

Invest in a good VHF radio, even a hand held. The US Coastguard may be able to triangulate a VHF signal, giving you even more protection against disaster.

When things go wrong, sometimes it’s a series of things, which could involve injury through an accident, exposure to elements, which may make it important to get help as soon as possible and so a GPS will enable faster assistance once coordinates are communicated correctly.