ECDIS

An Electronic Chart Display and Information System (ECDIS) is a navigation information system that complies with IMO performance standards and can be used as an alternative to paper charts for SOLAS V compliance. An ECDIS integrates Electronic Navigational Charts (ENCs) with position data from GPS/GNSS, AIS, radar overlay, and other navigation sensors to provide a continuous real-time picture of the ship's position relative to charted features, depths, and hazards. The legal basis for ECDIS is SOLAS Chapter V, Regulation 19.2.10, which made carriage mandatory in a phased schedule completed in 2018.

ECDIS performance standards are defined in IMO Resolution MSC.232(82) and implemented through the IEC standard IEC 61174. Manufacturers must certify their systems against these standards. Unlike paper charts, ECDIS is a type-specific system — every brand and software version has a different user interface — which is why STCW requires type-specific familiarisation rather than generic ECDIS training alone.

Mandatory carriage phasing — SOLAS V/19.2.10

The mandatory carriage schedule applied to ships on international voyages of 500 GT and above. All phases were completed by 1 July 2018:

Ship type	GT	New ships	Existing ships
New passenger ships	≥ 500 GT	1 July 2012	N/A — new build requirement only
New tankers	≥ 3,000 GT	1 July 2012	N/A
New cargo ships	≥ 10,000 GT	1 July 2013	N/A
New cargo ships	≥ 3,000 GT	1 July 2014	N/A
Existing passenger ships	≥ 500 GT	N/A	1 July 2014
Existing tankers	≥ 3,000 GT	N/A	1 July 2015
Existing cargo ships	≥ 50,000 GT	N/A	1 July 2016
Existing cargo ships	≥ 10,000 GT	N/A	1 July 2017
Existing cargo ships	≥ 3,000 GT	N/A	1 July 2018

Chart formats: ENC, RNC, and RCDS mode

Electronic Navigational Chart (ENC)Vector data
IHO S-57 (production) / S-100 (next-generation, transitioning from 2024)
ENCs are official government-issued charts in structured vector format. Each ENC cell covers a geographic area at a specific scale. ECDIS can display ENCs at any scale but must warn when displaying at a larger scale than the cell was compiled for. S-57 ENCs remain the primary format; S-100-based ENCs (S-101) are being issued by selected hydrographic offices from 2024 and will eventually replace S-57.
Raster Navigational Chart (RNC)Scanned raster image
IHO S-61 (BSB format, ARCS in UK)
RNCs are scanned versions of paper charts. They contain no embedded data structure — depth values, objects, and text are all part of the image. An ECDIS using RNCs operates in RCDS (Raster Chart Display System) mode, which provides reduced functionality and safety features compared to ENC mode.

RCDS (Raster Chart Display System) mode is the operating mode when RNCs are used instead of ENCs. RCDS is considered an inferior mode: the chart cannot automatically highlight hazards based on the ship's safety contour, depth soundings are not machine-readable, and anti-grounding functions are limited to positional alarms. RCDS is only permissible when ENCs are not available for the area. When used, SOLAS requires a paper chart backup to compensate for reduced ECDIS functionality. PSC inspectors have found many ships operating in RCDS mode unnecessarily.

S-57 to S-100 transition

The IHO S-100 Universal Hydrographic Data Model is the next-generation standard replacing the 30-year-old S-57 framework. S-100 enables richer, more granular data (tidal prediction layers, real-time water levels, dynamic route information, high-density bathymetric data) and a more extensible data architecture. The S-101 product specification defines the next-generation ENC format under S-100. Several hydrographic offices — including the UK UKHO, Norway, Australia, and the US NOAA — began issuing S-101 cells in parallel with S-57 cells from 2024. Full transition will take many years; older ECDIS hardware may require software or hardware upgrades to display S-101 cells. IMO has not set a mandatory S-57 sunset date as of 2025.

Type-specific familiarisation — STCW Reg I/14

STCW Regulation I/14 places a duty on companies to ensure that officers who have not previously used the ECDIS type on board receive adequate familiarisation before assuming navigation duties. This is not a training course in the STCW sense — it does not require a Certificate of Proficiency. It is an ISM Code obligation: the company's safety management system must include familiarisation procedures for each ECDIS make/model in the fleet. In practice, companies issue maker-specific familiarisation check sheets signed by the officer and the Master. PSC inspectors verify these records. Generic ECDIS training (type-generic courses as per IMO Model Course 1.27) satisfies background competence but does not replace type-specific familiarisation.

Common PSC deficiencies

Charts not up to date — ENCs not updated since last port
SOLAS V/27 (charts to be kept up to date)
New dangers, depth changes, buoy repositioning, and NOTAM corrections are missed. PSC inspectors check ENC cell update dates against the weekly update service (e.g., AVCS, PRIMAR). Lack of evidence of a current ENC service subscription is detainable.
No evidence of type-specific familiarisation for officers
STCW Regulation I/14 (company responsibilities) / STCW A-I/14
Officers must demonstrate familiarisation with the specific ECDIS make and model installed, not just general ECDIS training. PSC inspectors ask officers to demonstrate functions (e.g., how to add a user chart, check safety contour, acknowledge alarms). Inability to demonstrate is a deficiency; repeat failures lead to detention.
Safety contour and safety depth incorrectly configured
SOLAS V/34 (voyage planning), IEC 62288 / IEC 61174
Incorrect safety contour (e.g., set to 0 m instead of vessel draft + UKC margin) means the ECDIS will not alarm when the ship approaches shallow water. Incorrect safety depth causes depth soundings to be displayed in the wrong colour, masking hazards. These misconfigurations are among the most safety-critical ECDIS failures and a primary focus of PSC inspections.
ECDIS used in RCDS mode without paper chart backup
SOLAS V/19.2.10 + MSC circular on ECDIS carriage
When operating in RCDS mode (RNCs only), SOLAS requires an appropriate folio of up-to-date paper charts as backup. Many operators are unaware of this requirement. RCDS mode should only be used when ENCs are genuinely not available for the area.
Alarm inhibition / masking
IEC 61174 (ECDIS performance standards), SOLAS V
Operators silence or suppress navigation alarms (safety contour crossing, off-track alarms) without proper authority. The ECDIS internal log records alarm history; PSC inspectors review this log.

El Faro and ECDIS lessons

The 2015 loss of the US ro-ro vessel El Faro in Hurricane Joaquin (33 lives lost) highlighted ECDIS-adjacent lessons even though the ship was not ECDIS-fitted. The vessel's navigation was based on outdated weather information and a route that did not account for the hurricane's track. The NTSB investigation found that the crew relied on a single, delayed weather forecast source without cross-checking alternatives, and the Master failed to alter course in time. The lessons applied to ECDIS-fitted ships include: (1) ECDIS does not replace mariners' judgment — automated safety contours and alarms are only as good as their configuration; (2) chart accuracy depends on underlying hydrographic survey data — ECDIS cannot add soundings that were never collected; (3) over-reliance on any single system, including ECDIS, without cross-referencing radar, depth sounder, and visual lookout, remains a primary cause of groundings.

Backup arrangements — the four-condition rule

SOLAS V/19.2.10 requires one ECDIS as the primary means of navigation. The backup arrangement must be equivalent to the primary chart requirement. In practice, backup is provided by:

Two independent ECDIS units — the most common arrangement on new-build ships. Both must be connected to independent position sensors. A single GPS failure must not disable both ECDISs simultaneously; independent power supplies are required.
ECDIS + paper charts — permitted but increasingly rare for new ships. Paper charts must cover the entire intended voyage and be kept up to date via NtM/NtMs.

SN.1/Circ.266/Rev.1 (MSC, 2015) clarifies the backup conditions. The four conditions under which ECDIS may be used as sole means of navigation (without paper chart backup) are: (1) operating in ENC mode (not RCDS); (2) ENCs are available and up to date for the entire route; (3) the ship carries a second independent ECDIS; (4) the second ECDIS has an independent power supply and independent position source.

Cyber security

ECDIS is an increasingly recognised cyber attack surface. Most modern ECDIS units run on commercial off-the-shelf operating systems (Windows XP, Windows 7, Windows 10) and connect to the ship's network for chart updates, AIS overlays, and sometimes voyage data recorder integration. Vulnerabilities include: outdated operating systems without security patches; USB-based chart updates introducing malware; network connections bridging OT (operational technology) and IT systems; GPS spoofing or jamming feeding false position data into ECDIS. IMO MSC-FAL.1/Circ.3 (2017) and the IMO Resolution MSC.428(98) (2017, mandating cyber risk management in ISM SMS from January 2021) apply to ECDIS as part of the ship's integrated bridge system. BIMCO guidelines on cyber security recommend isolating ECDIS on a segregated network, disabling unused ports, and maintaining software at manufacturer-supported versions.