2 NAVIGATIONAL AIDS AND RELATED MATTERS
Guidance on chart datums and the accuracy of position on charts
2.1 The Technical Working Group considered the United Kingdom proposal (NAV 44/7/9) for a draft text of an SN Circular containing recommendations/guidelines with respect to the safety aspects of the use of different geodetic datums, as discussed by the Technical Working Group at NAV 43, taking into account the proposal by IEC (NAV 43/7/4), and prepared the draft text of an SN Circular containing guidance on chart datums and the accuracy of positions on charts, given in annex 1. The Working Group invited the Sub-Committee to instruct the Secretariat to convey annex 1 to IHO for consideration and submission of their comments to NAV 45.
2.2 he Working Group recounted that at NAV 43 the Sub-Committee had requested the IEC to include in IEC 61162-1 a datum message to warn users if a datum in use was not WGS 84 and inform the Sub-Committee accordingly. The Working Group was pleased to receive a report from the IEC that various of the digital sentences within the standard IEC 61162-1 had received further development. One of these DTM-datum reference-has now been completed and is included in the draft 2nd edition of IEC 61162-1, which is currently being circulated for comment, and is expected to be
published in early 1999.
Marine electronic systems and the Year 2000 problem
2.3 The Working Group considered the United Kingdom proposal (NAV 44/7/5), drawing attention to the range of problems associated with marine electronic systems and date changes, commonly known as the 'Millennium' or 'Year 2000 problem', including those related to the rollover of the coding used in the GPS system.
2.4 The Working Group noted that the Committee had already issued guidance on this matter through MSC/Circs.804 and 864 and was of the opinion that this was sufficient.
2.5 The delegation of the United States provided the following information concerning GPS."The GPS Joint Program Office has determined that all generations of GPS satellites are unaffected by the Year 2000 (Y2K)and GPS End of Week (EOW)Rollover Issues. However, the Civil GPS users may need to verify that their receivers and applications will work properly through these events."
DGNSS Stations on the Brazilian coast
2.6 The Working Group noted the information provided by Brazil (NAV 43/INF.2) containing a list of DGNSS stations on the Brazilian coast including a map with the nominal range of stations and noted that these stations provided differential corrections for use with GPS receivers.
