3.8.1 Position fixing and monitoring

When using paper charts, the need to plot positions at regular intervals keeps the navigator actively involved with monitoring the progress of the voyage. He is required to frequently look at the chart and will quickly detect if the vessel is being set off the course towards danger. He will also be looking ahead to the next waypoint and be noting any dangers close to the track.

With ECDIS there is the risk of losing this high level of situational awareness as the navigator’s role becomes increasingly passive. A quick glance at the ECDIS may be considered enough to note the vessel’s position and whether or not the vessel is on the courseline, but this is not sufficient to ensure the safety of the vessel, to confirm the integrity of the automated position fixing or to maintain awareness of hazards ahead.

It is therefore essential that navigators maintain an active role and continueto manually plot positions at regular intervals to confirm the positiondisplayed on the ECDIS is correct. There have been cases of vessels running aground because the navigator did not notice that GPS positioning had been lost, and the ECDIS was running in DeadReckoningmode. A warning message should appear on the display when DR positioning is being used.

3.8.2 Acronyms associated with ecdis

AIO Admiralty Information Overlay

APC Appropriate paper chart folio

ARC Admiralty Raster Chart

AVCS Admiralty Vector Chart Service

CBT Computer-based training

DR Dead Reckoning

ECDIS Electronic Chart Display and Information System

ECS Electronic Chart System

ENC Electronic Navigational Chart

GNSS Global Navigation Satellite System

GPS Global Positioning System

IHO International Hydrographic Office

IMO International Maritime Organisation

MIO Marine Information Objects

RCDS Raster Chart Display System

RIO Radar Information Overlay

RNC Raster Navigational Chart

RO Recognised Organisation

SENC System Electronic Navigational Chart

SMS Safety Management System

SOLAS Safety of Life at Sea

STCW International Convention on Standards of Training, Certification and Watchkeeping for Seafarers

TSS Traffic Separation Scheme

WGS84 World Geodetic Datum

XTE Cross track error

3.8.3 Electronic chart types

There are two different types of electronic charts in use with ECDIS and all navigation officers must be aware of their differences and limitations.

1. Electronic Navigational Charts (enc)

Commonly referred to as ‘vector charts’, are layered with digital information enabling the mariner to electronically interrogate features on the chart such as buoys, navigational marks, traffic separation schemes (TSS) and safety contours with detailed information displayed for the user. ENCs provide the mariner with a clear picture of the navigational situation without distorting the chart display when the scale is reduced.

ENCs enable the ECDIS to set different types of navigational alarms to act as a warning to the mariner. These warnings are usually visual as well as audible and give a clear indication of any dangers that lie ahead. The navigational alarms can include such hazards as shallow depths, shoals and isolated dangers as well as minimum under-keel clearance (provided the ship’s echo sounder is integrated with the ECDIS andthe draught details and alarm parameters have been correctly specified). Early warning alarms of approaching waypoints and alteration of course points, position fixing reminders and changing electronic chart alarms can also be specified within the alarm parameters.

ENCs are named and identified by an eight-character code (for example GB 600100). The first two characters identify the producer (for example GB = Great Britain, FR = France).

Each Unit in the Admiralty ENC Service has a 6-character identifier. The First Threecharacters are used in the same way as cell names. The First Two Characters are letters and indicate the producer nation. The third character shows the ‘usage band’ into which the cell falls. The usage band designator indicates the intended navigational purpose of the ENC, and will take one of the following values: