The subtle but important distinction between an ECDIS and an ECS

Many think that because they use electronic charts on their ship they have an ECDIS. Nothing could be further from the truth. ECDIS stands for Electronic Charts Display and Information System and ECS stands for Electronic Chart System.

Whilst the difference is subtle it is very important. The ECDIS specifications have been defined by various organizations and approved by IMO. The very definition of ECDIS means that to meet the carriage requirements users MUST use official Electronic Navigation Charts (ENCs). If you have a type approved ECDIS on your ship, using ENCs produced by a Private Data Provider makes your machine revert to the status of an ECS.

The IMO regulations stipulate that when carrying a type approved ECDIS with official ENCs, navigators meet the carriage requirements and thus can reduce their paper chart indices. This is not so for ECS.

Using an ECDIS therefore reduces the expenses associated with the carriage of paper charts: initial purchase, replacement, freight, correction service, etc. There are other advantages too that are difficult to quantify including improved safety, navigators training and comfort with the new technology, voyage recording and playback capabilities and others.

The criteria for official ENCs have been defined (and changed many times) and are listed in the S-57 specifications. Unfortunately these criteria were defined at a time when few hydrographic offices around the World were in a position to produce ENCs in this format (many still are not). This fact resulted in two trends of philosophy, one followed by the Hydrographic Offices and the other one followed by Private Data Providers (PDP).

C-Map, Transas and Navionics and others are “en-block” referred to as “Private Data Providers - PDP”. These companies realized that they had the know-how to produce Vector charts in what is technically the same or very close to the description of S-57. However they are not hydrographic offices and therefore their data cannot be considered as official and should be referred to as “Electronic Chart Database- ECD”.

Whilst some Hydrographic Offices invested in technology and production capability to produce and distribute S-57, some did nothing (due to lack of resources or interest or other reasons). Others created technology to produce Raster format, which is a facsimile of the paper charts, and a few years ago IMO approved that in the absence of official ENCs, the type approved ECDIS could use official Raster charts.

Further information on Electronic Navigation Charts, including ECDIS vs. ECS, the variety of data, Private Data Providers, the value of ENCs, coverage and AIS, can be found in George Arts’ newsletter in ‘Latitude Longitude’, issued by Marine Press of Canada. Click here to download the newsletter.

Contacts: George Arts,

Howard Snaith,