ECDIS & Passage Planning: A Complete Deck Officer's Guide

SOLAS ECDIS Requirements

SOLAS Chapter V Regulation 19.2.10 established phased carriage requirements for ECDIS, with large vessels (passenger ships and tankers over 3,000 GT, cargo ships over 50,000 GT) required to comply from 2012, and all remaining SOLAS vessels — including cargo ships down to 500 GT — required to carry an approved ECDIS by 2018. This phased implementation ensured the global fleet transitioned systematically, though port state control (PSC) deficiencies related to ECDIS compliance remain common.

On vessels over 3,000 GT, two ECDIS units are required. Where a single ECDIS is fitted on smaller vessels, an approved paper chart portfolio (or equivalent back-up arrangement accepted by the flag state) must be maintained. The display standard is governed by IHO S-52, which defines how chart data should be rendered visually on screen. Equipment must meet the IMO performance standard IMO MSC.232(82) — any system not complying with this circular cannot be used as the primary means of navigation.

Critically, STCW imposes a dual training requirement. Every officer using ECDIS must hold both a generic ECDIS certificate (based on IMO Model Course 1.27) and a type-specific training certificate issued by the manufacturer for each ECDIS model fitted on board. Generic training covers universal operational concepts, whereas type-specific training addresses the unique menu structure, alarm management, and safety-critical settings of a particular manufacturer's system. PSC inspectors routinely verify these certificates during port inspections and have detained vessels where type-specific certificates were absent or out of date.

Electronic Navigational Charts (ENCs) and RNCs

An Electronic Navigational Chart (ENC) is the official vector chart data set produced by a national hydrographic office and distributed in IHO S-57 format. Unlike raster images, ENCs are structured databases where every feature — soundings, coastlines, buoys, traffic separation schemes, restricted areas — is an individually addressable object with associated attributes. This allows ECDIS to interrogate chart objects, trigger alarms based on safety-critical attributes, and display information contextually depending on the selected display mode (Base, Standard, or Custom/All).

Each ENC cell carries metadata including edition number, issue date, and update number. ENCs must be kept current — updates are distributed through services such as AVCS (Admiralty Vector Chart Service), PRIMAR, or IC-ENC. Automatic update downloads should be applied weekly at minimum; a vessel arriving at a PSC inspection with a large update backlog — particularly one covering weeks of uninstalled updates — is at risk of a deficiency. Updates are cumulative and safety-critical: they may introduce newly surveyed hazards, wrecks, or amended traffic separation scheme boundaries.

An important distinction exists between ENCs and Raster Navigational Charts (RNCs). An RNC is a digitised scan of a paper chart, such as those distributed under the ARCS (Admiralty Raster Chart Service). An RNC displayed on an ECDIS-type screen does not constitute an ECDIS under SOLAS — it is only suitable for backup or reference. Primary navigation must be conducted using S-57 ENC data on a type-approved ECDIS.

Every ENC cell carries a CATZOC (Category of Zone of Confidence) attribute that describes the accuracy and reliability of the sounding data. CATZOC A1 indicates full area search, position accuracy better than 5 metres, and depth accuracy within 0.5 metres — typical of recently surveyed, well-maintained port approaches. CATZOC C indicates a controlled survey with limited accuracy, while CATZOC D denotes data from poor quality surveys with significant positional uncertainty. CATZOC U means the survey quality is unassessed. In any area displaying CATZOC D or U, the officer of the watch must increase the UKC allowance significantly and treat charted depths with caution.

Critical ECDIS Settings for Safe Navigation

Incorrect configuration of ECDIS safety parameters is one of the most dangerous operational errors a bridge team can make — and one of the most frequently cited PSC deficiencies. Before departure and whenever the vessel's loading condition changes significantly, the following settings must be reviewed and updated:

• Safety Contour: The depth contour that ECDIS uses to define the boundary between navigable and potentially dangerous water. It must be set to the vessel's maximum static draft plus the required UKC allowance (which accounts for squat, heel, dynamic rise and fall, and any height of tide correction). ECDIS will alarm if the planned route or vessel position crosses into water shallower than the safety contour. Setting this value too shallow (e.g., matching the maximum draft exactly without UKC) creates a false sense of safety.
• Safety Depth: An independent value (in metres) below which individual spot soundings are highlighted on the display in a contrasting colour. This supplements the safety contour by drawing the OOW's attention to individual shallow patches that may not be covered by the contour shading alone.
• Shallow Contour: A user-defined contour displayed in a distinct colour to indicate areas shallower than a set value. Typically set shallower than the safety contour, it provides an additional visual warning layer on the display.
• Deep Contour: A contour beyond which water is considered unrestricted for the vessel. Areas deeper than this contour are displayed in a separate shade, allowing the OOW to quickly identify deep-water corridors.
• Anti-Grounding Cone (Look-Ahead Alarm): A configurable sector projected ahead of the vessel's bow that continuously checks for dangers within a set time-to-go or distance threshold. If the cone intersects a danger — a shallow patch, restricted area, or safety contour — the ECDIS triggers an immediate alarm. The cone must be set appropriately for the vessel's speed and the navigational environment; an overly narrow or short cone in confined waters significantly reduces safety margins.
• Chart Datum: All modern ENCs and GPS receivers use WGS-84 as the horizontal datum. However, awareness is required when using older converted charts or coastal regions where local geodetic datums have been applied. A datum shift between the chart and the GPS position source can introduce positional errors of tens or even hundreds of metres — potentially catastrophic in confined waters.

Passage Planning — The Four Phases (SOLAS V Reg. 34)

SOLAS Chapter V Regulation 34 requires every ship to carry out voyage planning prior to proceeding to sea. The IMO Resolution A.893(21) — Guidelines for Voyage Planning — defines the four recognised stages. Each stage must be documented and the completed passage plan signed by the Master before departure.

1. Appraisal

The appraisal stage involves gathering all information relevant to the intended voyage before a single waypoint is plotted. Primary sources include: Admiralty Sailing Directions (Pilots) for coastal and port approach information; the List of Lights for light characteristics and ranges; the List of Radio Signals for VTS frequencies, reporting requirements, and pilot boarding arrangements; Tidal Atlases and tide tables for tidal stream predictions; and Ocean Passages for the World for ocean-going routes.

The OOW must also review current NAVTEX and NAVAREA navigational warnings for the route area, obtain weather routing advice where available, check the vessel's draught limitations against port tide windows, and review the company UKC policy. Any Traffic Separation Schemes (TSSs), Deep Water Routes (DWRs), mandatory ship reporting systems, or areas to be avoided must be identified at this stage and incorporated into the planning phase. Appraisal forms the foundation of the plan — errors or omissions here propagate through every subsequent stage.

2. Planning

The planning stage is where the passage is plotted on ECDIS from berth to berth. Waypoints are entered with planned courses and speed legs. For each leg, the planned UKC at critical points must be calculated and recorded, taking into account expected tide and squat. No-Go Areas (NGAs) — graphical danger areas drawn on the chart — should be marked around shoals, wrecks, and other hazards that must not be entered under any circumstances.

The ECDIS route check function must be run and all alarms reviewed before the route is approved. The planner must also define abort waypoints — positions prior to channel entries or port approaches at which the Master must decide to proceed or turn back based on conditions. Emergency anchorage positions should be identified. The written narrative passage plan — detailing critical waypoints, wheel-over positions, TSS entry and exit points, pilot boarding positions, and contingency actions — must be completed and presented to the Master for review and signature.

3. Execution

The execution phase begins when the vessel departs and must follow the approved route unless circumstances require deviation. ECDIS route monitoring is activated and the vessel's position — sourced from the primary GPS/GNSS and at least one independent secondary source — is continuously plotted against the planned track. Position must be cross-checked by at least two independent methods: in coastal and pilotage waters, visual bearing lines, radar bearing and distance from fixed objects, and continuous echo sounder readings supplement the GPS fix.

Fix frequency increases as navigational hazards are approached: open ocean fixes every 4 hours are standard, coastal passage fixes every 30–60 minutes, and pilotage water fixes every few minutes or continuously in real-time. The OOW must brief the Master at each significant waypoint handover. All fixes and positional cross-checks should be recorded in the bridge logbook with times.

4. Monitoring

Monitoring is not a discrete stage but a continuous process throughout the entire voyage. It involves constantly comparing the vessel's actual progress against the approved plan and responding promptly to any deviation. The OOW must remain alert to: cross-track error developing on the ECDIS display, NAVTEX or NAVAREA warnings received en route that may indicate new hazards, changing weather or sea conditions that affect the safe speed or planned routing, and AIS or radar targets that require course or speed adjustments.

If a significant deviation from the planned track is required — for instance, diverting to avoid traffic or weather — the OOW must not simply steer off track and return. A formally amended route or a new route must be created in ECDIS and approved by the Master. Undocumented deviations from an approved passage plan expose the vessel, officer, and company to serious liability in the event of an incident.

AIS Integration with ECDIS

ECDIS displays Automatic Identification System (AIS) targets overlaid directly on the ENC. Class A AIS transponders — fitted on all SOLAS vessels over 300 GT on international voyages — transmit dynamic data (position, COG, SOG, heading, rate of turn) and static data (vessel name, MMSI, call sign, dimensions, type, destination, ETA). This allows the OOW to identify contacts by name and assess their intentions before establishing radar contact.

However, AIS is emphatically not a collision avoidance tool under COLREGs. Rule 5 requires a proper lookout by all available means — which includes AIS — but AIS supplements rather than replaces radar and visual watchkeeping. AIS data can be inaccurate due to incorrect manual input, GPS errors, or deliberate manipulation. GPS spoofing has become an increasingly documented risk, particularly in certain geographic regions, where vessel positions displayed on AIS may differ materially from actual positions. Any target showing abnormal SOG, impossible rate of turn, or a position inconsistent with the radar picture should be treated with suspicion and cross-checked independently.

Radar-ECDIS overlay — where live radar video is superimposed on the ENC display — enables direct comparison of radar targets with charted features and AIS identifiers. This is a powerful tool for positional verification and collision avoidance assessment, but requires careful calibration of radar heading and position data to ensure accurate overlay alignment.

Parallel Indexing on ECDIS

Parallel indexing (PI) is a technique originating in radar navigation that remains best practice even when ECDIS is the primary navigation system. A parallel index line is drawn on the chart at a set perpendicular distance from the planned track, aligned with a radar-conspicuous object — a headland, lighthouse, fixed platform, or isolated buoy. As the vessel proceeds, the OOW monitors the vessel's position relative to the PI line: if the vessel is maintaining the planned track, the radar contact with the index object should remain at a constant range equal to the perpendicular distance.

The value of PI on ECDIS lies in its independence from the GPS position source. If GPS position is corrupted, spoofed, or suffering from a systematic error, the PI technique will reveal the discrepancy because the radar range to the index object will not match the planned PI distance. A convergence of PI range with the charted position confirms the GPS is accurate; a divergence demands immediate investigation. For this reason, PI lines should be pre-planned during the passage planning phase and specific radar-conspicuous objects identified for each PI segment.

Common PSC Deficiencies Related to ECDIS

Port State Control inspectors under the Tokyo MOU, Paris MOU, and USCG port state control regimes consistently identify the following ECDIS-related deficiencies:

• ECDIS type-specific training certificates missing or expired — the most common deficiency; even a single officer without a valid type-specific certificate for the onboard ECDIS model can result in a detention.
• ENC updates not applied — a backlog of uninstalled chart updates, particularly where updates contain new hazards, is a serious safety deficiency.
• Safety contour set incorrectly — set too shallow (not accounting for UKC) or, paradoxically, too deep (resulting in constant false alarms that officers have learned to ignore, defeating the safety purpose entirely).
• Passage plan not reviewed or approved by Master — SOLAS V Reg. 34 requires Master approval; a plan without a Master's signature is non-compliant.
• Backup navigation system not available or not maintained — the required backup arrangement (paper charts or second ECDIS) must be functional and covered by current chart folios.
• ECDIS not connected to an independent position source — the position source feeding the ECDIS must be independent of the primary GPS (e.g., a second GPS receiver on a separate antenna); using the same GPS receiver via a data splitter does not constitute an independent source.

Oral Exam Tips — ECDIS & Passage Planning

ECDIS and passage planning are core topics in OOW and Chief Mate oral examinations. Examiners test both factual recall and the candidate's ability to apply concepts in scenario-based questions. Commonly tested areas include:

• Name and describe the four phases of passage planning. Candidates must name all four (Appraisal, Planning, Execution, Monitoring) in order and describe the purpose and activities of each — rote recitation without practical context rarely satisfies an experienced examiner.
• Define CATZOC and its significance. Know that CATZOC A1 is the highest quality, be able to explain what CATZOC D/U means operationally, and state what action you would take in a CATZOC D area.
• Distinguish safety contour from safety depth. Safety contour is a depth area boundary that alarms when the vessel approaches or crosses it; safety depth is the value below which individual spot soundings are highlighted. They serve different visual and alarm functions.
• Explain what happens when a route monitoring alarm triggers. The OOW must assess the cause immediately — is it a genuine cross-track deviation, a GPS error, an unexpected set, or a system alarm? The vessel's actual position must be confirmed by independent means before any corrective action is taken.
• Explain the dual ECDIS training requirement under STCW. Both generic (Model Course 1.27) and type-specific training are mandatory; generic training alone is insufficient, and the type-specific certificate must correspond to the exact ECDIS model on board.

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