The NOAA ENC data are in International Hydrographic Organization (IHO) S-57 format, which is the data standard for the exchange of digital hydrographic data. Nautical chart features contained within a NOAA ENC provide a detailed representation of the U.S. coastal and marine environment. This data includes coastal topography, bathymetry, landmarks, geographic place names, and marine boundaries. Features in a NOAA ENC are limited in that they only represent the geographic region depicted in that particular ENC. Aggregating nautical features from all NOAA ENCs in the creation of GIS data results in a contiguous depiction of the U.S. coastal and marine environment.To learn more about S-57, visit the IHO website.For questions or comments, contact us.File naming conventions and scale bands    [Top]ENC Direct to GIS data is organized by scale band, and there are six scale bands available: Overview, General, Coastal,Approach, Harbour, and Berthing.SCALE RATIOS:Overview scale band consists of ENC files with a scale band of smaller than 1:1,500,000. General scale band consists of ENC files with a scale band from 1:600,001 – 1:1,500,000. Coastal scale band consists of ENC files with a scale band from 1:150,001 – 1:600,000. Approach scale band consists of ENC files with a scale band from 1:50,001 – 1:150,000. Harbour scale band consists of ENC files with a scale band from 1:5,000 – 1:50,000. Berthing scale band consists of ENC files with a scale band of larger than 1:5,000. The ENC filename is stored in the attribute named DSNM from the “coverage_area” feature layer.  The third character within the filename is a numeric value referencing to the following scale band category.  For example, a filename of US2EC02M.000 indicates that it is within the General scale band category.1 = Overview 2 = General 3 = Coastal 4 = Approach 5 = Harbour 6 = BerthingTo learn more about the object attributes for each S-57 object, see the S-57 Object Catalogue.