What are the main sources of nautical chart data?

Every line, symbol, and feature that you find on a nautical chart represents the work of scientists, surveyors, and cartographers who collect and analyze the data needed to create these important tools. To ensure that mariners can navigate safely through our coastal regions, the information contained on nautical charts must be accurate and up to date. NOAA’s Office of Coast Survey leads the creation and maintenance of our nation’s nautical charts, using data from many sources.

Why do nautical charts need to be updated?

A nautical chart isn’t something you can make once and forget about. Over time, our coastal environments can change. Coastlines can shift, tides and currents can reshape the seafloor, and human-made structures can be added to or removed from a coastal region. To keep people safe on the water, NOAA regularly collects and receives new data that is used to update charts to reflect current conditions. Some commonly updated features are listed below.

1. Water depths and underwater hazards
   Storms, waves, and currents can alter the seafloor or move objects such as rocks and debris. By updating depth measurements and the locations of underwater hazards, cartographers ensure mariners avoid running aground or striking hazards below the surface.
2. Dredged channels
   Many U.S. ports and coastal waterways rely on maintained channels to support maritime commerce. As ships get larger, channels may need to be deepened, widened, or even reshaped. When this happens, charts must be updated to match the channel’s new dimensions.
3. Shorelines
   Coastlines are constantly evolving due to erosion, sediment build-up, storms, and human development. Charts need accurate shoreline data so mariners know exactly where the sea ends and the land begins.
4. Aids to navigation
   Aids to navigation, such as buoys, beacons, and navigational lights, help guide vessels safely along coastal or hazardous areas. Navigation aids can be added, relocated, upgraded, or even removed by the U.S. Coast Guard. When this occurs, charts must be updated to ensure mariners know which signals they should expect to find in a particular area.

Where does the data for nautical charts come from?

To create complete and accurate nautical charts, NOAA cartographers combine hydrographic data, or information about the water and seafloor, with topographic data, or information about the land's features. This information can come from several sources.

The entities listed above provide more than 70% of the information NOAA uses to create and maintain nautical charts. Additional information is often provided by other federal, state, and local agencies, regional initiatives, international organizations, private survey companies, professional groups, other NOAA line offices, and even private citizens who report hazards or changes they encounter while on the water.

Every year, the Office of Coast Survey receives thousands of data submissions. Each one is reviewed, and if approved, is transformed into the symbols, depth, boundaries, and other features that appear on nautical charts. Together, NOAA staff produce about 18,000 charts annually.