IMO approves standards for raster chart display systems

Sea Technology, Sep 1998

In late July, the International Maritime Organization's Sub-Committee on Safety of Navigation (NAV 44) overwhelmingly approved an amendment to the existing ECDIS (electronic chart display & information system) performance standards that will allow ECDIS navigation systems to operate in a raster chart display system (RCDS) mode. Under the proposal, national maritime administrations may allow vessels the option of using the RCDS mode of operation until the vector electronic navigational chart (ENC) coverage required for the normal mode of operation is available. While operating in the RCDS mode, vessels will be required to use an appropriate folio of paper charts as determined by the national administrations.

For confused landlubbers (and the occasional editor), ECDIS is a navigation system that uses official vector ENCs and meets agreed IMO performance standards. RCDS is a navigation system capable of using official raster navigational charts. These are created by scanning original film materials used to produce printed (official) paper charts and electronically registering them to each other. The proposed amendments to the ECDIS performance standards permit those systems to be used in the RCDS mode where ENCs are not yet available.

Capt. Nicholas Prahl, director of NOAA's Coast Survey, has helped lead the charge to "legalize" raster charts as an interim electronic chart system until vector charts are available for ECDIS. (See Sea Technology, June 1998, pp. 77-79.) "The action taken at NAV 44 is entirely consistent with NOAA's strategy of producing ENCs for the nation's 40 largest ports and expanding coverage thereafter as resources become available," said Doug Brown, staff cartographer. For waters not covered by ENCs initially, NOAA raster nautical charts will provide the official electronic chart coverage.

Raster nautical charts already cover much of the world and the concept of ECDIS operating in an RCDS mode is seen as a way of letting mariners maximize the use of the system while ENC coverage expands. This is commonly referred to as the "dual-fuel" mode of operations. The important benefit of the dual-fuel approach is that electronic chart navigation based entirely on official and up-to-date charts is available for almost any voyage.

If approved by the IMO's Marine Safety Committee this coming December, manufacturers will have a set of criteria governing the performance and reliability of ECDIS systems operating in the RCDS mode. This will give the mariner the full, legal benefit of electronic charting now with greater improvements to be achieved as ENC coverage increases.