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tide tables and atlases, and the latest Notices to Mariners. These can be obtained from an ADMIRALTY
Distributor.
10.8.2 During the execution and monitoring of MASS voyages, including testing and trials of MASS, it is again advised
that official navigation products, services and data should be used, including Notices to Mariners and other
bulletins. As outlined in Para 10.7.1, ADMIRALTY Distributors can supply these products. However, it is recognised
that these products are intended for humans to use whilst on board navigating a vessel and as such may not
offer the optimum solution for autonomous navigation systems. To that end the UK Hydrographic Office is making
richer data sets available that can be used within the MASS navigation system during execution and monitoring
of MASS operations. These data sets include:
n AIS data;
n Tidal almanac data;
n ENCs;
n High resolution gridded bathymetry;
n Environmental Protected Areas;
n Wrecks;
n Cables;
n Anchorage areas;
n Vessel manoeuvring restrictions and constraints.
10.8.3 Furthermore, the UK Hydrographic Office is working on the International Hydrographic Organisation’s (IHO) next
generation of navigation products and standards, collectively known as the S-100 standards. These new standards
will begin to replace the ENC data standard (S-57) and will introduce new standards for navigation data sets such
as gridded bathymetry and tidal data. These standards are still under development. However, in the future they
will become the IMO mandated standards in manned shipping and are therefore likely to be endorsed for
unmanned shipping. Sample data sets for trial purposes can be downloaded from the UKHO’s ADMIRALTY
website https://discover.admiralty.co.uk/access-data/s-100.
10.9 RESILIENCE OF POSITION FINDING
10.9.1 A navigation system must be able to provide continuity of service; that is the determination of a vessel’s position,
to an acceptable level of accuracy in all circumstances which may be encountered during the vessel’s intended
operations.
10.9.2 Resilience should be delivered through the selection of sources of positional information which offer independent
Primary, Tertiary and Backup sources of position. It should be accepted that a drop off in accuracy may be
inevitable with the loss of higher tier sources of position, however the three tiers of position finding should enable
the vessel to be safely navigated throughout the voyage in the event of disruption to two of the minimum three
sources of positional information. It is prudent to consider the Primary and Tertiary sources in the context of
maximising accuracy, while a Backup source should be that which provides the greatest resilience when used
with the appropriate navigation techniques and processes.
10.9.3 By examining the sources and applicable navigation techniques and processes available during each of the
stages of the vessels intended operations it should be possible to identify the most appropriate Primary, Tertiary
and Backup sources of position, recognising that these may change based on the area and nature of the operation.
10.9.4 In more complex systems, the use of Inertial Navigation Systems (INS) to bridge the gap between disruptions
and outages may be of benefit.
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