The 43rd session of the IMO's Subcommittee on Navigation (NAV 43), held July 14-18, 1997, considered Performance Standards for Raster Chart Display Systems (RCDS). The Standards permit an ECDIS to operate with official raster navigational charts (RNCs) whenever ENCs are not available. By an overwhelming majority, the Technical Working Group of NAV 43, comprised of delegates from over twenty nations, supported the Standards and recommended that they be approved in plenary. The Standards include the following provisions as a means of ensuring the highest level of safety for mariners navigating with official raster chart data:
- Carry of a folio of up-to-date paper charts, as determined by national authority, when operating an ECDIS in the RCDS mode.
- Promulgation of IHO product specifications for RNCs, so that data supplied by national hydrographic offices are used in a manner that enhances the safety of navigation by meeting the requirements of the RCDS Performance Standards.
- Issuance of an IMO Circular in conjunction with the RCDS Performance Standards, advising national authorities of the differences between RCDS and ECDIS operation.
Although a consensus on approval of the Standards could not be reached in the NAV plenary, the IHO/IMO Harmonizing Group on ECDIS (HGE) was invited to reconsider the Standards to reach a compromise acceptable to more delegations.
At the eighteenth session of HGE (London, Sept 15-16, 1997), experts in hydrography and marine navigation approved the Performance Standards for RCDS making only minor revisions. In addition, to more systematically validate RCDS across a range of sea conditions and traffic situations, HGE sanctioned the conduct of formal sea trials. These are to be conducted by Russia, UK, US, and Australia with preliminary results expected in early 1998.
Opponents of RCDS are concerned that acceptance of RCDS as SOLAS-compliant might slow progress toward ECDIS, which offers greater benefits. The counter argument, supported by the United States and many other major maritime nations, is that raster and vector are a complementary solution with raster serving as a natural stepping stone from paper to vector. This approach allows a substantial improvement in marine navigation safety by the use of high quality official raster nautical charts while ECDIS data coverage expands. "Dual-fuel" navigation systems such as the kind being tested aboard P&O vessels transiting between Hong Kong and Singapore validate this as a natural evolutionary path.
There is no evidence that the availability of RCDS and raster charts will deter mariners from adopting ECDIS when the data become available. Because the performance standard for RCDS is nearly identical to the ECDIS standard, hardware which supports RCDS should also support ECDIS. The move from RCDS to ECDIS would therefore only be a software upgrade so cost should not be an issue.
Although ECDIS is the goal -- and hydrographic offices are working hard to produce the necessary vector Electronic Navigational Charts for ECDIS -- RCDS will ensure that mariners are afforded the full, legal benefits of electronic charting now.