📚 This article is part of the “ECDIS Masterclass Series”
Part 1 | Part 2 | Part 3 | Full Guide
🧭 Introduction to ECDIS – Basics of Modern Marine Navigation
This Introduction to ECDIS explains the Electronic Chart Display and Information System — a computer-based navigation tool that displays Electronic Navigational Charts (ENCs) and integrates data from GPS and other bridge sensors.
It provides a real-time display of the vessel’s position and motion, offering greater situational awareness and navigational safety than traditional paper charts.
🔹 Primary Functions of ECDIS
- Continuous display of vessel position and motion
- Route planning, monitoring, and correction
- Integration with radar, AIS, log, gyro, and echo sounder
- Real-time safety features: grounding alarms, safety contour, cross-track limits
- Chart management, updates, and ENC permit handling
⚙️ Purpose of ECDIS in Navigation
The purpose of ECDIS is to replace paper charts with an advanced digital system that meets IMO standards.
ECDIS functions both as a navigational aid and a legal chart carriage requirement under SOLAS, provided it meets IMO MSC.232(82) performance standards and uses official ENCs.
Furthermore, ECDIS enhances safety, reduces officer workload, and ensures instant access to up-to-date navigational information — helping officers make quick, informed decisions during critical maneuvers.
📜 ECDIS Regulatory Framework
The operation and performance of ECDIS are defined by international regulations:
- IMO Resolution MSC.232(82): Performance standards for ECDIS
- SOLAS Chapter V, Regulation 19: ECDIS carriage requirements
- IEC 61174: Operational and testing standards
- IHO S-57 / S-63 / S-52: Data formats, encryption, and symbology
- STCW Convention: Requires certified ECDIS training
👉 Key Point:
Every vessel using ECDIS must carry updated official ENCs for its trading area, and bridge officers must be trained and type-specific familiarized.
For full IMO details, visit the IMO MSC.232(82) Resolution.
You can also explore data standards at the International Hydrographic Organization (IHO).
🌐 ENC vs RNC – Electronic Chart Formats in ECDIS
ECDIS can display two types of charts: Electronic Navigational Charts (ENCs) and Raster Navigational Charts (RNCs).
| Type | Full Name | Format | Source | Scale Range | Legal for Primary Navigation? | Notes |
|---|---|---|---|---|---|---|
| ENC | Electronic Navigational Chart | Vector | Authorized Hydrographic Office | Varies by cell | ✅ Yes | Supports layers, alarms, and data interrogation |
| RNC | Raster Navigational Chart | Raster (scanned paper) | Authorized Hydrographic Office | Fixed | ⚠️ No (backup only) | No alarms or layer control |
🧩 ECDIS ENC Structure and Usage Bands
Each ENC is divided into cells representing different scales and usage bands:
| Band | Scale Range (approx.) | Purpose |
|---|---|---|
| 1 – Overview | 1:3,500,000 and smaller | Ocean passage planning |
| 2 – General | 1:1,500,000 to 1:3,500,000 | Coastal overview |
| 3 – Coastal | 1:350,000 to 1:1,500,000 | Coastal navigation |
| 4 – Approach | 1:90,000 to 1:350,000 | Port approach |
| 5 – Harbor | 1:22,000 to 1:90,000 | Harbor maneuvering |
| 6 – Berthing | Larger than 1:22,000 | Pilotage and berthing |
🗺️ ECDIS ENC File Naming and Data Structure
Each ENC cell follows the IHO S-57 format and is encrypted under S-63 for data security.
It contains multiple object layers such as depth contours, coastlines, and navigational aids.
Example ENC File Name: GB5X01S1.000
| Code | Meaning |
|---|---|
| GB | Country code |
| 5 | Usage band (Harbor) |
| X01 | Cell reference |
| S1 | Sub-cell identifier |
| .000 | Edition number |
⚓ Raster Navigational Charts (RNC) in ECDIS
Raster Navigational Charts (RNCs) are scanned images of official paper charts.
Unlike ENCs, they are image-based and cannot trigger alarms or hide/display layers.
RNCs are used in Raster Chart Display Systems (RCDS) as a backup where ENCs are unavailable.
💾 Updating ECDIS Charts and ENCs
ECDIS requires weekly updates to maintain safe navigation.
Updates are provided through AVCS (Admiralty Vector Chart Service) or PRIMAR and include:
- New buoys or navigational aids
- Depth and wreck updates
- Temporary and Preliminary (T&P) notices
- New edition releases
Update File Types
| Extension | Description |
|---|---|
.000 | Base edition |
.001, .002, etc. | Weekly updates |
.031 | 31st update of the chart |
Update Methods
- Automatic: via USB or network connection from supplier
- Manual: entering corrections from update logs when needed
🧠 ECDIS Display Modes and Chart Layers
ECDIS allows the user to customize visible layers depending on navigation requirements:
| Mode | Description |
|---|---|
| Base Display | Always visible; coastlines, safety contour, and own ship |
| Standard Display | IMO-recommended view for normal navigation |
| All Display | Shows every available chart object |
| Custom Display | User-defined layer combination |
🧭 Summary – Why ECDIS Matters
This Introduction to ECDIS highlights how the system revolutionized navigation by replacing paper charts with a real-time, sensor-integrated digital display.
It enables bridge officers to plan, monitor, and update routes safely while staying compliant with SOLAS and IMO regulations.
Understanding ECDIS functions, updates, and safety settings is a core competency for every navigating officer.
👉 Read next: ECDIS Alarms and Safety Contour Settings Explained
👉 Continue with: How to Update ENCs in ECDIS Step-by-Step
📚 This article is part of the “ECDIS Masterclass Series”
Part 1 | Part 2 | Part 3 | Full Guide
⚠️ Disclaimer
This article is for educational and training purposes only. Always follow your company’s Safety Management System (SMS), official manuals, and manufacturer instructions when operating ECDIS or performing navigational tasks.
Merchant Navy Life and the author are not liable for any actions taken based on this guide.
All rights received © Merchant Navy Life.