ECDIS Alarm Settings: How to Stay Compliant and Safe

by Charles Hays August 12, 2025

The Electronic Chart Display and Information System (ECDIS ) is the beating heart of modern bridge navigation. It provides real-time situational awareness, integrates with radar and AIS, and allows navigators to plan and monitor voyages with a precision that paper charts could never match.

But technology is only as safe as the parameters you give it. One of the most critical—and often underestimated—elements of ECDIS operation is alarm configuration. Correctly setting these alarms is not just “best practice”; it is required under IMO MSC.232(82) (ECDIS Performance Standards) and reinforced by MSC.1/Circ.1503 (ECDIS – Guidance for Good Practice).

Failing to configure them properly risks two extremes:

Alarm fatigue – where constant, unnecessary beeping leads watchkeepers to ignore alerts.
Silent danger – where hazards pass undetected because thresholds were never set or were set too wide.

This guide will walk you through the mandatory alarms, explain how to set safe parameters, and offer best practices to keep your vessel safe and compliant.

Why Alarm Settings Matter

ECDIS alarms serve as the digital “lookouts” on your bridge (they are not to replace actual lookouts on the bridge). They continuously monitor your planned route, vessel position, and surrounding conditions. The moment something threatens to put you into unsafe water, collision risk, or navigational error, they provide an audible, visual, and persistent warning.

An incorrectly set alarm is like posting a lookout who can’t tell a rock from a wave—it defeats the purpose.

Mandatory Alarms Under IMO Standards

The IMO Performance Standards require an ECDIS to generate alarms or indications for at least the following situations:

Safety Contour Crossing – entering shallow water.
Safety Depth – approaching areas less than your minimum safe depth.
Cross Track Distance (XTD) exceeded – straying too far from the planned route.
Look-Ahead Anti-Grounding Alarm – detects hazards in your path within a set time.
Route Deviation & Waypoint Approach – off-track navigation or nearing a turn.
Chart Update Alarm – notifying when ENCs are outdated.
CPA/TCPA – collision risk alerts when integrated with AIS/ARPA.

1. Safety Depth & Safety Contour

Safety Depth is the shallowest depth you consider safe, calculated as:

$Safety Depth = Draft + Under Keel Clearance (UKC)$

Once entered, ECDIS will bold all soundings equal to or less than this depth on the ENC.

Safety Contour is the depth contour separating safe water from unsafe water. If your ship crosses this contour, the ECDIS triggers an alarm. The contour must be set to equal or greater than your safety depth and must match one of the contour intervals in the ENC (e.g., 5 m, 10 m, 15 m).

2. Cross Track Distance (XTD)

XTD defines how far you can deviate laterally from your planned track before triggering an alarm. This ensures you remain in a pre-surveyed safe corridor.

Typical values:

Open ocean: 0.5–1.0 NM
Coastal waters: 0.2–0.5 NM
Pilotage/harbor approaches: 0.05–0.1 NM

Some ECDIS units allow different port and starboard XTDs—useful if hazards lie closer on one side.

3. CPA/TCPA Alarms

When ECDIS is linked to AIS or ARPA radar, it can calculate:

CPA (Closest Point of Approach) – the closest another vessel will pass if both maintain current course and speed.
TCPA (Time to Closest Point of Approach) – the time until that closest approach happens.

The CPA/TCPA alarm activates if another vessel will approach within your set distance and time limits.
Example: CPA limit = 1.0 NM, TCPA limit = 12 min. If another vessel will pass 0.8 NM away in 10 min, the alarm sounds.

Best Practices for ECDIS Alarm Settings

Base Parameters on Actual Conditions – Adjust for voyage stage: looser settings in open ocean, tighter in confined waters.
Synchronize Both ECDIS Units – Dual setups must match exactly to prevent confusion.
Avoid Alarm Fatigue – Set thresholds that are meaningful, not over-sensitive.
Document Settings – Include them in your passage plan and logbook.
Check the Ship’s Safety Management System (SMS) – Always confirm alarm configurations are in line with your company’s SMS procedures, which may include flag state or class-specific requirements.
Test Before Departure – Use simulation mode to verify alarm functionality.

Consequences of Non-Compliance

Incorrect alarm settings can lead to:

SOLAS breaches – under Chapter V Regulation 19.
Port State Control detentions – if alarms aren’t correctly configured.
Increased liability – if a navigational incident occurs due to alarm mismanagement.

Conclusion

ECDIS alarm settings are your silent watchkeepers, but only if configured correctly. By understanding Safety Depth, Safety Contour, XTD, and CPA/TCPA, and by applying IMO guidance from MSC.232(82) and MSC.1/Circ.1503, you ensure compliance—and more importantly, you safeguard your vessel, crew, and cargo.

Treat alarm setting as a formal part of your voyage planning, not as an afterthought, and it will repay you with safer, more efficient navigation.

Disclaimer:
This article is provided for informational purposes only and is not intended as a substitute for official guidance. Vessels must consult their respective Flag State requirements and their company’s Safety Management System (SMS) when configuring ECDIS alarm settings.