SOLAS Chapter V · Navigation & Bridge
ECDIS & Berth-to-Berth Passage Planning Checklist: Safety Contour, UKC & CATZOC
Safety of Navigation (SOLAS Chapter V) consistently ranks in the top three deficiency categories across every Port State Control MoU, and Chapter 4 (Navigation and Communications) is one of the highest-observation chapters in SIRE 2.0, RightShip RISQ 3.2 and CDI. Inspectors do not merely check that a passage plan binder sits on the chart table — they sit beside the Officer of the Watch at the ECDIS console and ask them to demonstrate safety contour settings, automatic route checks, T&P Notice to Mariners overlays and independent radar parallel indexing.
This guide covers the complete ECDIS setup and passage planning checklist under SOLAS V/19.2.10, V/27 & V/34, IMO Resolution A.893(21), IMO Resolutions MSC.232(82) & MSC.530(106) / MSC.1/Circ.1503/Rev.2 and MSC.1/Circ.1705 (2026 ENP Guidelines).
Updated · Written by SeaReady in our own words. Not affiliated with OCIMF, RightShip, CDI, any MoU or any administration — always check the current official documents.
1. ECDIS Four Depth Parameters, UKC & CATZOC (SIRE 2.0 Ch. 4)
Under SOLAS Regulation V/19.2.10 (mandatory ECDIS and independent back-up arrangement carriage) and the IMO ECDIS Performance Standards in Resolution MSC.232(82) and Resolution MSC.530(106) (introducing IHO S-100 / S-98 interoperability for new installations from 1 January 2026 / mandatory 1 January 2029), every navigating officer on watch must be able to calculate and explain the four ECDIS depth settings for the current leg of the voyage (ocean, coastal, approach and berth/pilotage) without guessing:
| ECDIS Parameter | How It Is Calculated | What It Controls on the ENC & Inspector Check |
|---|---|---|
| Safety Contour | Static / Dynamic Draught + Squat + Safety Margin (UKC) − Height of Tide (only where company SMS permits tidal window) | Marks the boundary between safe and unsafe water on the ENC, triggers the anti-grounding alarm in the look-ahead sector, and bolds the contour line. If the exact calculated metre value does not exist as an ENC contour, ECDIS automatically selects the next deeper contour. |
| Safety Depth | Static / Dynamic Draught + Squat + Company UKC Margin | Controls which spot soundings are highlighted in bold black text (soundings equal to or shoaler than the Safety Depth) versus grey text (soundings deeper than the Safety Depth). Does not by itself trigger the anti-grounding contour alarm. |
| Shallow Contour | Ship’s Static / Dynamic Maximum Draught (zero UKC grounding depth) | Subdivides the unsafe water inside the Safety Contour into two shades of blue: dark blue inside the Shallow Contour (where the ship will definitely ground) and medium blue between the Shallow Contour and Safety Contour. |
| Deep Contour | Typically 2 × Ship’s Draught (or the depth at which shallow-water squat effects begin) | Marks the boundary beyond which the ship experiences deep-water conditions with negligible shallow-water squat or bank interaction. |
| CATZOC / ZOC Depth & Position Allowance | IHO S-57 / S-101 Category of Zone of Confidence (A1, A2, B, C, D, U) | Accounts for hydrographic survey depth uncertainty (e.g. ZOC B = ±1.0 m + 2% depth, ±50 m position; ZOC C = ±2.0 m + 5% depth, ±500 m position) when calculating required Under-Keel Clearance and cross-track limits. |
| Look-Ahead Sector (Time / Distance & Width) | Coastal/Pilotage: e.g. 3–6 min (or 0.5–1.0 nm); Open Sea: e.g. 12–15 min | Defines the guard zone ahead of the ship that scans the largest-scale ENC for the Safety Contour, isolated dangers, traffic separation schemes and user danger areas. Over-wide or 60-minute settings in pilotage waters cause continuous alarm fatigue. |
- Squat & Dynamic UKC Calculation: Calculate maximum squat for both open water and confined channels (using the vessel’s block coefficient $C_B$ and planned speed over ground) and verify that net Under-Keel Clearance remains above the company’s minimum UKC policy (e.g. ≥ 10%–15% of deepest draught in coastal/channel waters or ≥ 0.60 m alongside).
- ENC permits, S-63 / S-52 / S-100 status & weekly updates: Verify that all ENC cells for the intended berth-to-berth voyage are installed and up to date to the latest weekly Notice to Mariners on both the primary and independent back-up ECDIS, and that the IHO Presentation Library (S-52 PresLib 4.0 / MSC.1/Circ.1503/Rev.2) is current.
2. Berth-to-berth passage planning: IMO Resolution A.893(21)
Under SOLAS Chapter V Regulation 34 and IMO Resolution A.893(21) (Guidelines for Voyage Planning), every voyage plan must cover the complete track from berth to berth (including pilotage waters) across four stages:
| Stage | IMO Reference | Required Bridge Team Action & Evidence |
|---|---|---|
| 1. Appraisal | IMO Res. A.893(21) § 2 | Gather all hydrographic and operational information from berth to berth: up-to-date ENCs and T&P Notices to Mariners, Admiralty Sailing Directions / e-NP (IMO MSC.1/Circ.1705), List of Lights, List of Radio Signals (VTS/pilotage reporting points), tide tables, currents, load-line seasonal zones, MARPOL Special Areas / ECAs, and company UKC policy. |
| 2. Planning | IMO Res. A.893(21) § 3 | Plot the berth-to-berth route on the largest-scale ENCs; set leg-by-leg XTD (cross-track distance), speed limits, turn radii, wheel-over points (WOP), parallel index (PI) lines, abort points, no-go areas, VTS/SRS reporting lines, ECA fuel changeover positions and echo-sounder/extra-lookout activation marks; run the automatic Route Check and inspect every warning visually. |
| 3. Execution | IMO Res. A.893(21) § 4 | Master reviews and signs the passage plan before departure and holds a bridge-team passage briefing; verify ETA against tidal windows, squat at planned speeds, bridge equipment pre-departure tests (SOLAS V/26 steering gear & 12-hour checks), and upload the validated route to both primary and back-up ECDIS units. |
| 4. Monitoring | IMO Res. A.893(21) § 5 & STCW Code A-VIII/2 | Continuously cross-check primary GNSS position using independent position-fixing methods (radar parallel indexing, visual bearings, radar range/bearing and echo sounder) at intervals plotted on the chart; never rely on GPS/ECDIS alone. |
3. Electronic Nautical Publications (IMO MSC.1/Circ.1705) & Bridge Equipment
Alongside ECDIS, Port State Control officers and vetting inspectors verify nautical publications, bridge recorders and mandatory reporting marks:
- Electronic Nautical Publications (ENP — IMO MSC.1/Circ.1705, July 2026): Check that digital Sailing Directions, Lists of Lights, Lists of Radio Signals (including VTS and mandatory ship reporting systems under SOLAS V/11), Tide Tables and the current IAMSAR Manual Volume III (SOLAS V/21, hard-copy working copy on the bridge) are corrected to the latest Notice to Mariners, with an independent emergency-powered back-up.
- Mandatory Ship Reporting Systems (SRS) & ECA boundaries plotted on the chart: Plot every mandatory VTS/SRS reporting line (such as CALDOVREP, OUESSREP, WETREP, FINREP, STRAITREP, BELTREP, SOUNDREP, MASTREP), MARPOL Special Area boundary and 0.10% m/m ECA fuel changeover start/completion position directly as user chart notes on the route.
- VDR / S-VDR, BNWAS, AIS & LRIT (IMO Res. A.1206(34)): Verify that the Voyage Data Recorder (VDR) has a current annual Certificate of Compliance and zero active fault alarms, the Bridge Navigational Watch Alarm System (BNWAS) is switched on at sea with the key under the Master’s control, AIS static/voyage data matches the current port call, and the LRIT Conformance Test Report is on board with the terminal operating (absence or switching off of LRIT without flagging is an explicit detainable ground under IMO Resolution A.1206(34)).
Questions seafarers ask
What is the difference between Safety Contour and Safety Depth on ECDIS?
The Safety Contour is the depth contour line that divides safe water from unsafe water, changes the chart colour shading, and triggers the ECDIS audible/visual anti-grounding alarm when crossed by the ship’s route or look-ahead vector (if the exact calculated depth is not an encoded ENC contour, ECDIS defaults to the next deeper contour). The Safety Depth is a numerical value that only highlights spot soundings equal to or shoaler than that figure in bold black font; crossing a bold spot sounding inside the Safety Contour only triggers an alarm if "Isolated Danger" detection in safe water is enabled.
What does IMO MSC.1/Circ.1705 (July 2026) require for Electronic Nautical Publications (ENPs)?
Under IMO Circular MSC.1/Circ.1705 (Guidelines for Electronic Nautical Publications under SOLAS V/19.2.1.4, V/19.2.1.5 and V/27, issued 6 July 2026), where nautical publications (Sailing Directions, Lists of Lights, Lists of Radio Signals, Tide Tables) are carried digitally on an ENP system, the primary and back-up computer hardware must be independent, the back-up must operate from the emergency source of power, and both units must carry current weekly Notice to Mariners updates available for immediate bridge use without needing live internet connectivity at sea.
Do deck officers need both generic and type-specific ECDIS training certificates?
Under STCW Regulation I/14 and Table A-II/1 / A-II/2, every Master and Deck Officer standing a navigational watch on an ECDIS-equipped ship must hold an approved Generic ECDIS training certificate (IMO Model Course 1.27) AND documented familiarisation on the specific make and model of ECDIS installed on board (in accordance with the Flag Administration’s circular and the company’s SMS familiarisation checklist) before taking charge of a navigational watch.
How do SIRE 2.0 and PSC inspectors verify that an ECDIS passage plan was properly checked?
Inspectors ask the Navigating Officer (2/O) or OOW to open the active or most recent berth-to-berth route on ECDIS and demonstrate: (1) how the Shallow Contour, Safety Depth, Safety Contour and Deep Contour were calculated for each leg (including dynamic squat and CATZOC uncertainty); (2) the automatic Route Check log with all safety contour, isolated danger and T&P NMs warnings reviewed; (3) manual AIO (Admiralty Information Overlay) / T&P corrections plotted with mariner’s notes; and (4) regular cross-checking of GNSS position by radar Parallel Indexing (PI), visual fixes and echo-sounder history.
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