Doug King: GPS and chart plotters are very common now in boating. They're great aids to navigation, but they're no substitute for proper seamanship. There are a number of things you must be aware of, and the first is that they're only an aid to navigation. The second thing is if you have a data card that uses a map display, make sure it's up-to-date. That means that your charts and displays will show all the dangers and features.
You need to be competent in how to read a chart and to understand chart symbols. The machine has to be set up to the Australian datum, which is WGS 84 or WGS 1984. Most GPS plotters will have common functions; things such as waypoints, routes, tracks, those sorts of things. And they're very, very useful. Waypoints allow you to put a point in on the chart, or as a latitude and longitude, and ask the unit to take you to that place. It will give you a compass heading and the time it will take to get there, depending on your speed.
There are also go-to functions, where you can place a cursor on the chart and say, go to that spot. If you're going to use these functions, it's important that you know what's between you and your destination, because the plotter will take you in a straight line. And if there are dangers in between, it will take you right over the top. So, you need to plan and understand your route, and always monitor where you're going.
The zoom function on plotters is also something to be wary of. As you zoom out to a smaller scale, some features may drop off, so use the largest scale zoom possible when you're navigating. Avoid using the highway mode on its own. It doesn't show you any chart information or dangers. Chart plotters and GPS are a great aid, but they're no substitute for keeping a proper lookout and monitoring your progress at all times.