Chart Updates

New Information Added to Charts

Critical Corrections

New data for chart updates is categorized as being either "critical" or "routine." Critical data includes any changes that may pose a danger to navigation 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 to the positions or characteristics of aids to navigation, such as buoys, beacons, and lights.

NOAA applies critical corrections to its electronic navigational chart (NOAA ENC®) product and these updates are released as ENC update files, which have sequentially numbered filename extensions, such as .001, .002, etc.

Routine Corrections

All non-critical data is categorized as "routine." This includes the results of ordinary hydrographic and shoreline surveys, which can be extensive and may take longer to compile into ENCs than critical corrections. Any specific dangers revealed during routine surveys or the application of other routine data are extracted from the data and classified as critical corrections.

Smaller routine changes are usually released within an ENC update file. Larger routine changes are often released in a new edition, called an ENC base file, which has a filename extension of .000 and is often called a "triple zero file." New editions may also be released after many updates for an ENC have been issued.