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A historical paper chart from 1968 of the Potomac River from Mattawoman Creek to Georgetown.
The simplest definition of cartography is that it is the art and science of creating maps that represent the Earth’s physical surface. In contrast, nautical cartography — while it is also about creating a representation of the physical world — focuses on the navigable waters and the conditions in and around it that may affect marine navigation.
Since nautical charts are maps tailored to particular needs, nautical cartography requires a special set of skills. A nautical chart is both a tool and work area. Navigators actively work on a nautical chart, using its valuable information to plot their vessels’ courses through the water. To create U.S. nautical charts, NOAA nautical cartographers use data from many sources, including NOAA hydrographers and shoreline mappers, the U.S. Army Corps of Engineers, the U.S. Coast Guard, and many others. Once NOAA cartographers receive the data, they interpret it, review its quality, and format it — ensuring that it is easy to understand and ready to be incorporated into a nautical chart.
A NOAA Corps officer plots a course on the bridge of the NOAA Ship Nancy Foster offshore of Puerto Rico.
NOS cartographers use sophisticated geographic information software and techniques to produce charts to exacting specifications. Every chart and each piece of data included on a chart is a bit different. This means nautical cartographers must use their best judgment about which features to include on a chart, how to portray them, and how any included features may affect the understanding and interpretation of other features on the chart.
The natural environment can change dramatically over time as a result of natural processes. Rivers deposit silt, which changes the shape of coastlines as well as channel and harbor depths. Storms affect the shape of barrier islands and the passages between them. Strong storms may create hazards to ship traffic if heavy wind and rain wash debris into the waterway.
People and their activities also change the environment. Dredges scoop out sediment, silt, weeds — and sometimes garbage — from channels and harbors to make these areas easier to navigate. Buoys are moved to mark the edges of the deepest water in channels that change often. Piers, wharfs, and port facilities may be built, improved, or destroyed, reconfiguring the size or shape of marinas. Bridges get built over navigable channels, and pipelines, power, or communication cables may be laid below them. Changes to recommended routes, anchorages, and regulated areas may all change over time as well.
These are just some of the thousands of changes that cartographers must update on nautical charts every year.
Historical paper chart of a preliminary survey of Anacapa and Santa Cruz Islands, off the coast of California in 1856. Some historical nautical charts depicted illustrations of prominent features, such as the headlands shown on this chart.
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