Abstract
NOAA Electronic Navigational Charts (NOAA ENC®) have been developed to support safe navigation in U.S. waters and are available for free download.  The NOAA ENC® are in International Hydrographic Organization (IHO) S-57 format, which is the data standard developed by the IHO to be used for the exchange of digital hydrographic data. NOAA ENCs can also be used for non-navigational purposes in Geographic Information Systems (GIS). In order for NOAA ENC® data to be used in GIS, the data must be translated from S-57 to a GIS-friendly format. The resulting data can be used for a variety of non-navigational purposes that involve geospatial analyses.

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 NOAA 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.