Chartplotters and/or charting apps on smartphones and tablets with GPS are almost universal on boats today. A primary function is to show your boat superimposed on a chart so that you know exactly where you are at all times. In addition, the use of waypoints and routes makes is easy to plan your course in advance and to steer efficiently once underway. If you are using a chartplotter or charting app, it's worth the time to learn how to set waypoints and use routes.
Unfortunately, the designers of chartplotters and apps have not standardized the methods by which one sets waypoints and makes routes, so you need to consult your manual or help screen to learn which buttons to press etc. to do these two functions. The following overview of procedures describes how to use waypoints and routes in a way generally true for all devices.
First, Set Waypoints
A waypoint is a specific position on a chart. You can make a waypoint for your dock or mooring, for example, to help guide you back home. You can also set a waypoint for your destination, and a string of waypoints to get you there if you need to make turns, follow a channel, etc.
When setting waypoints, remember that when sailing you may not be able to sail directly to a waypoint if it is upwind and you have to tack. You can either adjust waypoints for tacking or simply tack toward the upwind waypoint while observing the chart to ensure you remain clear of obstructions to either side.
The "Go To" Function
If you choose not to set a full route to a destination, you can use the "go to waypoint" feature of most plotters and apps. This is a simple procedure: simply set (or select) the waypoint and enable the "go to" function. The plotter then gives you the compass bearing to that waypoint and typically the distance (and time) remaining to reach it. The screen may also display an arrow for the direction to steer.
The "go to" function has one limitation it is important to be aware of. Even if you are constantly headed toward the waypoint, and had a clear path there from your starting point, the boat may be swept sideways by a current or the normal leeway of sailing. If you're not watching the chart, you might assume you are always on course as long as you're headed toward the waypoint - when actually you could be swept into a shoal area or another obstacle. Watch the bearing indicated on the plotter or app: if the bearing to the waypoint is changing over time, you are no longer on the straight line from your starting position. You can compensate for currents, however.
Making and Steering a Route
In most cases when you're not making a simple passage to a destination waypoint, it is worthwhile to make a route. A route is simply a line connecting two or more waypoints start to finish. With a route, you proceed from one waypoint to the next in an orderly sequence. Again, different plotters and apps have different processes for setting a route: you may simply click or tap a number of positions in sequence, or you may first set waypoints and then direct the route from one to another.
A great advantage of a route is that it shows as a line on the chart, so that you can continually see whether your boat is staying on the line and steer accordingly to avoid being swept off course by a current or the wind. As long as your route line does not cross any obstacles, you are safe while you stay on it.