NOAA Electronic Navigational Charts (NOAA ENC®) are in International Hydrographic Organization (IHO) S-57 format, which is the standard used for the exchange of digital hydrographic data. In ENC Direct to GIS, Coast Survey has translated the data from S-57 to a GIS-friendly format.
While features in a single NOAA ENC represent the geographic region that is depicted in that particular ENC cell, ENC Direct provides a continuous depiction of the U.S. coastal and marine environment.
Basic structure of NOAA ENC data
An ENC contains attributed vector spatial data of nautical chart features. Nautical chart features are organized in S-57 object classes. Attributes in an ENC further describe each nautical feature. Each ENC object class has predefined geometry types associated with it, e.g., point, line, area (polygon in ENC Direct to GIS). For example, the land area object class has both point and polygon geometry. An ENC can contain any of the predefined IHO object classes and attributes.