NOAA electronic navigational charts (NOAA ENC^®) are vector data sets that support all types of marine navigation. Originally designed for large commercial vessels, ENCs are used in computer navigation programs and mobile applications on many types of ships, including recreational vessels. NOAA ENCs provide real time ship positioning, as well as collision and grounding avoidance.

Updates for NOAA ENCs have historically been published weekly but updates are now being pushed daily, Monday through Friday. These updates include weekly Notice to Mariners corrections and additional critical changes, as well as the routine addition of newly compiled data, such as hydrographic or shoreline surveys. Critical updates include any changes that may pose a danger to navigation and that mariners should be informed of as soon as possible. This may include newly discovered rocks, wrecks, shoals, or other dangers to navigation, as well as changes in the positions or characteristics of aids to navigation (buoys, beacons, and lights). NOAA applies critical corrections to its NOAA ENC products and these updates are released as ENC revision files.

All non-critical data is categorized as "routine" and includes the results of ordinary hydrographic and shoreline surveys, which can be extensive. Routine source data is ONLY applied to NOAA ENCs and not to paper and raster nautical charts. Any specific dangers revealed during routine surveys or the application of other routine data are extracted from the data and classified as critical corrections to be applied to all products.

The chart updates viewer shows the areas that have changed on each ENC since its last new edition was published and can be found here: https://distribution.charts.noaa.gov/weekly_updates/.

NOAA ENCs may be downloaded through the Office of Coast Survey’s Chart Downloader page. These downloads are available through individual compressed files or pre-packaged compressed files here: https://charts.noaa.gov/ENCs/ENCs.shtml.