Charts are maps of the sea. As maps show distances, roads and railways, hills and woods and many other features of the land, so charts show distances over stretches of sea, the depth of the water round coasts, dangers to shipping such as rocks and sand banks, tidal currents, the position of lighthouses, marker buoys and other information vital to a sailor.
Charts are essential to the navigation of a ship. The navigator is the man who must plot the course of the ship, know exactly where the ship is and which direction she is travelling in, at every stage connected with charts is the compass rose, which shows all the principal points of the compass. A navigator needs this in order to relate his chart to the North Pole and so check the direction of the ship’s course. Another important item is a set of compass, or dividers. With these the navigator can measure off distance how fast his ship is moving and how long a voyage will last.
Special charts for yachtsmen include extra, useful information. Such charts will indicate which courses to follow if the yacht is under sail, and which stretches of water along the coast are safe and suitable anchorages.