NOAA ENC is a vector database of chart features built to the IHO's S-57 standard. NOAA's Office of Coast Survey, as the U.S. national hydrographic office, is exclusively responsible for production and authorization of NOAA ENC data in U.S. waters.

NOAA ENCs support all types of marine navigation by providing the official Electronic Navigational Chart used in ECDIS and in electronic charting systems. NOAA ENCs support real-time navigation, as well as the collision and grounding avoidance needs of the mariner, and accommodate a real-time tide and current display capability that is essential for large vessel navigation. NOAA ENCs also provide fully integrated vector base maps for use in geographic information systems (GIS) that are used for coastal management or other purposes.

Building and Maintaining NOAA ENCs
In 1997, NOAA began a process of building a portfolio of ENCs that encompass the same areas covered by NOAA’s suite of approximately 1,000 paper and raster charts. The ideal and most accurate way to build ENCs is to recompile the paper chart from all of the original source material. Unfortunately, this process is impractical as it is far too labor intensive. Instead, NOAA ENCs have been compiled from source on those features that are deemed to be navigationally significant. U.S. Army Corps of Engineers' federal project limits have been captured from large-scale drawings. These precise coordinates of channel limits are being incorporated into the ENC. Likewise, high-accuracy positions are being used to chart U.S. Coast Guard aids to navigation. The paper chart has been the source for the remainder of items.

NOAA has utilized private contractors to build NOAA ENCs. Private companies are provided high-resolution source information such as U.S. Army Corps of Engineers channel limits, and aids to navigation established by the U.S. Coast Guard. Contractors are also provided with the latest version of the paper/raster chart. All NOAA ENCs that are built by private contractors are reviewed by NOAA cartographers before they are posted on the Internet.

NOAA cartographers and private contractors (under NOAA supervision) apply updates to ENCs using high resolution original source material. As new source information arrives at NOAA headquarters, cartographers update NOAA ENCs using high resolution position and depth information.

Building Status
As of September, 2008, 670 NOAA ENCs are available for download. All of the major ports throughout the country now have NOAA ENC coverage. Many smaller scale coastal ENCs that connect these ports have been completed, while some are still in the building process. NOAA plans to continue its ENC building program in the upcoming years.

Updates for NOAA ENCs
NOAA’s goal is to provide weekly updates for each ENC it makes available. Update cells are posted on the Internet for download. When downloaded, these update cells can be applied to the base ENC cell to produce an up to date ENC.

Distribution of NOAA ENCs
NOAA ENCs are available as free downloads from the Internet. Mariners who wish to download NOAA ENCs directly and use the data to fuel ECDIS or ECS may do so.

In October 2005, NOAA created a new mechanism for distributing NOAA ENCs. NOAA announced certification requirements with standards for applicants who want to redistribute NOAA ENCs as official data. Two types of certification are offered. The first type, Certified NOAA ENC Distributor (CED), covers NOAA ENC downloading, exact copying, and redistribution of those copies. The second type, Certified NOAA ENC Value Added Distributor (CEVAD), permits reformatting official NOAA ENCs into a System Electronic Navigational Chart (SENC) using type-approved software, and distribution of that SENC. NOAA intends by this action to assure that, though redistributed, quality official NOAA ENC data is offered to the public in support of safe navigation on U.S. waters.

In order for an electronic chart to gain type approval as an ECDIS, it must be fueled by official ENC data. However, ENC data is not only for ECDIS use. ENCs can fuel any ECS that reads the S-57 format. Private vendors are free to download NOAA ENC data, reformat it into a proprietary format, and then resell that data.