Marine Glossary

|| || || || ||

DNC

Digital nautical chart. These are the NGA electronic counterparts of NGA paper charts intended for official government use (Navy, USCG). The charts are unclassified, but not available to the public—the sources involve many nations and there are likely copyright issues involved. These are vector charts (databases), but not compliant with ENC. (NOAA has converted a couple DNC to ENC for Central America, but this seems to have been focused on the IHO’s MACHC program, with no indication that others will follow.)

DNC are viewed on the Navy Navigation Sensor System Interface (NAVSSI), which is their equivalent of ECDIS. DNC can have many GIS layers, and can be integrated with command and control, weapons, and other systems. For those using DNC, there is a convenient source online for latest updates at dnc.nga.mil , which also shows graphic chart indexes and other information. (The downloads at this link are updates only for existing DNC on authorized software.) There is also there a Background link, which describes the charts generically.

There seems little hope that we will get echart access to international waters from NGA sources, so for US sourcing we are left with the several NGA paper versions available at official chart dealers—keeping in mind that NGA paper chart numbers and coverage do not correspond to the DNC numbers. The number and coverage of these charts has gone down considerably over the years. Captains Nautical Supply has a convenient display of NGA charts available by print on demand. The masters are provided by the NGA, but they are not updated and some if not most are very old. Each comes with an update notice such as 1990/41, meaning the last up date of this chart is in NTM 1990, week 41.

For ENC of international waters we need to refer to the IHO’s interactive chart index to see which nations offer which charts. There are several companies, including the British Admiralty, that sell official ENCs from all nations.

Our textbook Introduction to Electronic Chart Navigation covers the nuances of ENC usage and the special approach to chart reading they call for.