What kind of information does a chart provide — what does it tell us?

Nautical charts use unique symbols to provide a wide variety of information, such as the natural and human-made features, danger warnings, and navigational aids that can be found on land and in the water.

Nautical charts show natural features on land such as rivers and shorelines as well as topographic information like the differences in height between hills, mountains, and valleys. Human-made structures such as bridges, railroad tracks, and dams are also represented by unique symbols. These symbols are important for navigators to locate reference points along the shore and determine their location as they navigate along otherwise featureless coastlines.

In addition to land features, nautical charts have many symbols for natural and human-made features found in and on the water. Many of these features have been identified by hydrographers, or scientists who collect information about the ocean floor and what is in the water, and were added to nautical charts by cartographers, who are experts in the science and art of map-making.

An electronic navigational chart of Cape Ann, Massachusetts, displayed on an Electronic Chart Display and Information System, which incorporates chart information with real-time location data.

Natural features include water depth and the makeup of the ocean floor. Depending on the depth of the water, there may be different types of rocks, sand, or shoals. Shoals are natural underwater sand ridges, banks, or bars that make the water depth more shallow than in surrounding areas. Navigators have to know this information so they don’t run aground and damage their vessels.

Human-made features on nautical charts may include obstructions to navigation. For example, a sunken or beached shipwreck is a human-made feature and may pose an obvious danger to navigation. Abandoned vessels that may be anchored offshore, represent a similar danger to navigation. Certain areas of the ocean may not be obviously dangerous but should be avoided. One such example would be an area known to contain unexploded ordnance, or weapons such as bombs, shells, or mines that should have exploded when they were fired but failed to do so and are still at risk of exploding.

Charts also contain many symbols of human-made objects placed in the water to aid navigators with navigation, sort of like street signs on land. Examples of aids to navigation include buoys, fog signals, and landmarks. These devices or structures are designed to assist navigators in determining a safe course, or to warn of dangers.

Lines of latitude and longitude are two of the most essential navigational chart features. Latitude and longitude have been used for centuries as a precise system of determining our location anywhere on the Earth. Navigators must know how to determine their location according to latitude and longitude to ensure their safety and accurately navigate the world’s ocean and coasts.

	Rock which covers and uncovers or is awash at low water
	Underwater obstruction with a depth of 20 meters or less
	Dangerous wreck, depth unknown
	Submarine cable
	Aids to navigation
	Lights
	Sector lights
	Towers
	Church tower, spire, or dome
	Fog signal
	Built-up area
	Area where anchoring is prohibited or restricted, with other cautions