So, it's important to know where you are on a chart, But what if you have a chart plotter that shows your position? That's fine, but redundancy is key and comparing your position on the electronic chart with a paper chart is sound seamanship. Simply take the latitude and longitude reading from your GPS and using a straight edge and pencil, locate this on the side (latitude) and bottom (longitude) of the chart, draw the lines until they intersect, and that's your position. (Make sure the pencil is very sharp.) Then review your position on the chart, compare it with the plotter, and you'll feel more confident about your boat's position.