How GPS Works and How it Can Help You at Sea

If you have a boat and don’t use GPS, then you probably aren’t sure what one is or how it works. GPS stands for “Global Positioning System” and it is one of the most useful instruments that you could use at sea. By understanding how this incredible system works, you can understand how it can be used by other systems and why it is so important.

There is one belief about GPS that a lot of people have wrong. They believe that the instrument transmits information about them and their location to satellites. The opposite is actually true. These instruments don’t transmit any information, but instead receive atomic time codes from multiple satellites.

There are usually at least two dozen GPS satellites in orbit at all times. They are all running on the exact same atomic clock, are perfectly in sync, and transmit time codes at the exact same time. When your GPS receiver tries to show you exactly where you are, it receives multiple transmissions to triangulate your position.

The transmissions it receives aren’t received at the same time though. There is a variance due to the distance of the satellites and these variances help your receiver calculate your location. In order to calculate your two dimensional location (like on a map), your GPS needs at least three satellites. In order to calculate your three dimensional location (like on a map, plus your elevation in relation to sea level), it will need four satellites. What is amazing is that a GPS receiver can make all of these calculations in an instant.

This amazing technology can be applied to other instruments, such as a chartplotter. When added to a chartplotter, the user can look at a map of their course and know exactly where they are. Not only will they know where they are, they will be able to tell how fast they are going and how much longer until they reach their next way point or final destination. If the boater has strayed from their course, it will show up instantly. For these reasons, most new chartplotters include GPS features, and I would recommend you only buy a chartplotter with one installed.

Even if you don’t have a chartplotter with GPS tracking, you can still use a handheld receiver to determine your precise location. Though handheld units are usually less accurate than most other units, they are still able to be accurate within about 40 feet. This can come in handy when no landmarks are in sight and the chartplotter has become practically useless.

On top of these benefits, GPS has also been used in emergency beacons like EPIRBs and PLBs. These instruments are rare cases of a GPS location being transmitted. However, this transmission is done in order to save lives and must only be activated in the event of an emergency.

As you can see, GPS instruments can be very useful and have already been becoming the greatest boons in the maritime world. As time has gone on, they have become more and more accurate. Their accuracy has even helped save lives in emergencies. So, if you haven’t updated your boat’s navigational instruments lately to include GPS, then it’s about time you did.