The first step in using a GPS navigation system is solving for x,y, and z in the previous equation. Just kidding…as it turns out, you don’t need to understand a thing about how GPS actually works...but here are many ways it can help in diving.
The first step in using a GPS navigation system is solving for x,y, and z in a complicated base equation that won't even fit on this article page. Just kidding…as it turns out, you don’t need to understand a thing about how GPS actually works (much less solve its base equation) to have a great time using this technology in your diving adventures.
GPS, short for Global Positioning System. determines geographic position from anywhere on Earth, using a series of satellites that circle above the planet. GPS was first developed for military use by the US government. Today, GPS units are manufactured by many different companies, in a wide variety of models, for personal and recreational use. GPS units range start at about a hundred bucks and can go up to several hundred dollars.
Unfortunately, GPS technology does not work under water. (There are rumours about a US navy Super Secret Special GPS that can, but you’re not going to find it at your local sports store. Or any store.) Nevertheless, there are several techniques by which scuba divers can successfully use GPS to mark locations, create maps, and record their dives.
If you are new to GPS technology, you’ll want to learn the ins and outs of your unit on land. Practice marking and recording positions before you apply the technology to diving. You can simulate using a GPS to track a dive by tracking a walk through a large field or woods.
If you are diving with a team that includes a person who stays topside, the easiest way to use GPS is by keeping the unit with the team member at the surface, and indicating points to mark through tugs on a towline.
Most divers who use GPS do it by towing a surface unit. One way to tow a unit is to simply put it in a waterproof floating box designed just for that purpose, such as a Pelican case or the Otterbox 9000. Depending on your dive site you may wish to mount a dive flag on top, or simply use the box by itself.
This works well enough under most conditions, although not as well if there is a strong current, wind, or large waves at the surface. It’s a hassle to tow a surface unit while diving—not something you’re likely to want to do for every dive. As an occasional expedition to mark locations and/or record a particular dive path, however, GPS is a wonderful tool.
Another novel way to use GPS as a diver is to employ a reel. This method allows the diver to dive autonomously while using GPS. Some brands of GPS—most notably the Magellan Sportrak Map and Meridian series—have a feature that allows them to automatically “grab” a signal whenever they come back into GPS range after having been underwater, then continue to display the last data point they received after they pass out of range again. This means that a diver can take the unit with him or her on the dive, deploy it to the surface with a reel when he wants to mark a point, then reel in the unit with the location captured. The unit will need to stay at the surface for about sixty seconds to capture the reading before being pulled back down to the diver. A basic reel costs about $30.
