What's important to know about using a GPS unit safely and effectively?
Sue & Larry respond:
Global Positioning Systems have made modern-day navigation a breeze, but every prudent mariner knows never to depend upon a single system of navigation. So the first thing to know about using a GPS unit safely is that you should always confirm what it tells you by way of another method of navigation, preferrably a dead-reckoning plot.
Though using most GPS units is relatively easy and fairly straightforward, there are some serious pitfalls youíll want to avoid to ensure that you arrive safely at your destination. First, the waypoints you use need to be chosen from a reliable source (published guide book, reference book, etc.) or you need to have carefully taken them from an updated chart yourself. It's not uncommon for sailors to make mistakes during the process of physically entering the waypoint number into the GPS database. When entering waypoint data, you should double and then triple-check the numbers to ensure that you have not pressed any wrong buttons or transposed any of the digits.
After all your waypoints have been carefully entered, trace your route out on a chart to ensure that the direct line between waypoints doesnít place your course through non-navigable waters. Even with a system as accurate and sophisticated as GPS, itís always best not to take anything for granted.
Once youíre underway, confirm with your chart and your own eyes that the heading and course you're steering are logical. And last of all, donít let your use of a GPS unit displace good seamanship. Dead reckoning and basic chart plotting should always be used in combination with GPS-based navigation.