What are nautical charts?

Coast Survey throughout the years: operating a projection ruling machine in the WWII era (left), onboard the NOAA Ship Surveyor in 1990 (center), and a navigation response team vessel in 2025 (right), superimposed on historical charts (left and center) and the modern-day National Bathymetric Source (right).

Nautical charts have been used for centuries throughout the world to help navigators — people who direct vessels’ routes — plan their journeys through the ocean and along the coasts, by showing where their ships can and cannot safely travel.

Knowing how to safely navigate the world’s waterways is essential. The ocean is vast and can be very dangerous. Without proper training, guidance, and tools, such as nautical charts, it’s easy to get lost, and accidents can occur that cost lives, damage property and the environment, and impact businesses. Safe navigation is also necessary for recreational and commercial fishing, as well as for maintaining trade between national and international ports — activities that contribute to a healthy economy.

In some ways, nautical charts can be thought of as "road maps of the ocean," but are they really the same? While the two serve the same function — to plan a trip from one point to another — the information shown about the route is very different on a road map and a nautical chart. Nautical charts provide detailed information about hidden dangers so navigators don’t hit anything or run aground. Road maps provide no information about the conditions of a road. Nautical charts allow navigators to plot their own courses through open bodies of water and highly trafficked areas. Road maps show predetermined routes like roads and highways. Nautical charts provide hydrographic information, or information about the physical features of bodies of water — details like the water’s depth and whether an area’s ocean floor is muddy or rocky, for example — and information about the adjacent land, such as whether or not there are mountains. Nautical charts also depict obstacles to navigation, such as rocks and shipwrecks, and aids to navigation like buoys. Road maps don’t show traffic lights or informational markers, but they do show geographic information such as the political boundaries of cities, states, and countries. Because nautical charts are so important to safe navigation, commercial navigators — people who travel the ocean professionally to ship products and fish commercially, for example — are required by law to have updated nautical charts on board their vessels. Commercial travelers on land, like long-haul truck drivers, are not required by law to have updated maps in their vehicles.