Digital Charting Standards =========================== We're about to venture in to obscure acronym territory, so let's get some definitions straight. Make sure you understand the difference between Raster and Vector Charts (see :doc:`./digital_charts`) and then let's go. International Hydrographic Organisation --------------------------------------- `The IHO `_ coordinates the activities of national Hydrographic offices and sets standards for uniformity. They define the standards upon which all charts adhere to in terms of official standards. Official Charts --------------- Official Charts can ONLY be *issued by, or on the authority of, a Government, authorized Hydrographic Office or other relevant government institution.* All charts discussed from here in on concern officially recognised charts, not those issued by independant companies. Raster Navigational Charts ----------------------------- Raster Navigational Charts (RNC) are digital raster copies of official paper charts. They must meet standards set by the IHO, and are updated regularly through digital distribution. Electronic Navigational Charts ---------------------------------- Electronic Navigational Charts (ENC) are vector charts issued by an official body in compliance with IHO standards. They must use the latest data available to the hydrographic organisation, be updated regularly, and use WGS 1984 Datum. Electronic Chart Systems ------------------------ Electronic Chart Systems (ECS) are digital systems that can read raster and/or vector charts, but does not meet all the requirements for use as a standalone navigation system. ECSs can only be used to assist navigation conducted primarily via other means (such as paper charts). Electronic Chart Display and Information Systems ------------------------------------------------- Electronic Chart Display and Information Systems (ECDIS) are the international standard in dedicated digital navigation. An approved ECDIS system can be used as a **primary means of navigation** as long as adequate back up arrangements are maintained, typically complete duplication with independant power and position input or an up to date paper nautical chart folio. ECDIS systems must be approved, and also must be adequately maintained with software and chart updates. They are also dependant on maintenance of their data sources, such as RADAR, AIS and GNSS systems. ECDIS systems are mandatory for `most old and new commercial foreign going vessels `_ at this point in time. It is essential for those ships to have adequately trained officers and a well maintained ECDIS system in order to be compliant. Can I use Raster Navigational Charts and still be ECDIS Compliant? --------------------------------------------------------------------- They can be used for navigation in areas where ENCs are not available, but only with “an appropriate folio of up to date paper charts”. This means they can't be used independantly for navigation like an ENC on an ECDIS system could be, and also their use is only approved when there's no other option for digital navigation available.