What Is a Nautical Chart? A Complete Guide for Boaters, Sailors & Coastal Navigators

by Christopher O'Keeffe May 31, 2026

Why nautical charts remain one of the most important tools on the water—even in the age of GPS.

Long before electronic chartplotters, satellite navigation, and mobile apps, mariners crossed oceans, entered harbours, navigated reefs, and explored coastlines using one of the most important navigational tools ever created:

The nautical chart.

Today, despite extraordinary advances in marine technology, nautical charts remain an essential part of safe navigation.

Whether you're cruising the Whitsundays, fishing offshore Western Australia, exploring Tasmania's rugged coastline, crossing Bass Strait, or simply planning a day on the water, understanding how nautical charts work is one of the most valuable skills a skipper can possess.

At Mapworld, we stock one of Australia's largest ranges of official nautical charts, including Australian Hydrographic Service (AHS) AUS charts, WA DPI inshore charts, Imray cruising charts, tide tables, navigation equipment, and marine accessories.

This guide explains what a nautical chart is, what information it contains, why it matters, and how to choose the right chart for your vessel and cruising area.

What Is a Nautical Chart?

A nautical chart is a specialised map designed specifically for marine navigation.

Unlike a road map or topographic map, a nautical chart provides detailed information about:

• Water depths
• Coastlines
• Reefs
• Rocks
• Shoals
• Navigation markers
• Buoys
• Harbours
• Channels
• Tides
• Currents
• Maritime hazards

Its purpose is simple:

To help vessels navigate safely.

Modern nautical charts are produced using hydrographic survey data and are continually updated as conditions change. They remain one of the primary navigational references used by commercial shipping, recreational boaters, fishing vessels, naval operators, and sailing yachts worldwide.

Why Nautical Charts Are Different from Ordinary Maps

A road map shows what exists on land.

A nautical chart shows what exists above and below the water.

For mariners, the most important information is often invisible from the surface.

A nautical chart reveals:

⚓ Underwater hazards

⚓ Safe channels

⚓ Depth contours

⚓ Sandbanks

⚓ Reefs

⚓ Wrecks

⚓ Navigation aids

⚓ Tidal information

Without this information, even familiar waterways can become dangerous.

What Information Does a Nautical Chart Show?

One of the reasons nautical charts can appear intimidating to newcomers is the sheer amount of information they contain.

Every symbol serves a purpose.

Depending on scale and chart type, a nautical chart may show:

• Soundings (water depths)
• Depth contours
• Seabed composition
• Reefs and coral areas
• Rocks and obstructions
• Shipwrecks
• Navigation beacons
• Buoys
• Lighthouses
• Harbour facilities
• Jetties and marinas
• Tidal information
• Current flow data
• Anchorage areas
• Shipping channels
• Maritime boundaries
• Bridges and overhead clearances

Official hydrographic charts use internationally recognised symbols and standards so that navigators can interpret information consistently worldwide.

Understanding Water Depths

One of the most important functions of a nautical chart is showing depth.

Depths are usually displayed as numbers known as soundings.

These indicate the depth of water at specific locations.

Charts also use:

• Depth contour lines
• Shaded depth zones
• Hazard markings

to help navigators understand underwater terrain.

This allows skippers to quickly identify:

• Safe water
• Shallow areas
• Navigable channels
• Potential grounding hazards

Depth information is one of the reasons official nautical charts remain indispensable for coastal navigation.

Navigation Aids on Charts

A nautical chart also identifies aids to navigation.

These include:

• Lighthouses
• Beacons
• Buoys
• Leading lines
• Sector lights
• Day marks

These features help mariners determine position and safely navigate coastal waters.

Many charts include detailed information about light characteristics, colours, flashing patterns, and visibility ranges.

Why Nautical Charts Still Matter in the GPS Era

One of the most common questions from newer boaters is:

"Do I still need a chart if I have GPS?"

The answer is simple:

Absolutely.

GPS tells you where you are.

A nautical chart helps you understand what surrounds you.

Experienced navigators use charts to:

• Plan passages
• Assess hazards
• Understand water depths
• Identify alternate routes
• Evaluate anchorages
• Navigate when electronics fail

Many professional mariners still regard paper charts as one of the most important backup systems on board.

Modern electronic navigation is powerful, but safe seamanship still depends on understanding the water you're travelling through.

The Different Types of Nautical Charts

Not all charts are designed for the same purpose.

⚓ AUS Charts

AUS charts are official Australian Hydrographic Service charts.

They are the primary navigational reference for Australian waters and are required aboard many commercial vessels.

Mapworld stocks a comprehensive range of AUS-numbered charts covering:

• Queensland
• New South Wales
• Victoria
• Tasmania
• South Australia
• Western Australia
• Northern Australia
• Great Barrier Reef regions

Every AUS chart supplied by Mapworld is corrected to the latest Notices to Mariners at the time of dispatch.

🌊 DPI Inshore Charts

State DPI charts are designed primarily for recreational boating.

These charts often provide:

• Detailed inshore coverage
• Fishing grounds
• Local boating information
• Harbour detail
• Coastal navigation assistance

They are particularly popular with recreational fishers and trailer boat owners.

⛵ Imray Charts

Imray charts are among the world's most respected cruising charts.

They are based on official hydrographic information but are enhanced specifically for small-craft navigation and international cruising.

Popular cruising regions include:

• Mediterranean
• Caribbean
• Pacific Islands
• European waterways

Paper vs Laminated Nautical Charts

At Mapworld, most nautical charts are available in both paper and laminated formats.

Paper Charts

Ideal for:

• Traditional chart table navigation
• Passage planning
• Chart corrections
• Long-term storage

Many experienced navigators still prefer paper charts for plotting and voyage planning.

Laminated Charts

Ideal for:

• Cockpit use
• Open vessels
• Frequent handling
• Marine environments

Benefits include:

• Water resistance
• Improved durability
• Write-on/wipe-off capability
• Easier onboard use

Mapworld's laminated charts are especially popular with recreational boaters navigating exposed Australian coastal waters.

Australian Waters Demand Good Charts

Australia possesses one of the world's longest and most diverse coastlines.

From:

• The Kimberley
• Ningaloo Coast
• Perth waters
• Bass Strait
• Port Phillip
• Sydney Harbour
• Moreton Bay
• Whitsundays
• Great Barrier Reef

navigators encounter dramatically different marine environments.

Many regions contain:

• Coral reefs
• Shoals
• Strong tidal flows
• Shifting sandbanks
• Narrow channels
• Remote anchorages

Accurate charting is essential for safe passage planning.

This is why official hydrographic charts remain such an important part of Australian boating.

Beyond Charts: Essential Marine Navigation Tools

Charts work best when combined with other navigational tools.

Mapworld's marine collection also includes:

🧭 Marine compasses

📏 Parallel rules

📐 Navigation plotters

✏️ Dividers

📘 Cruising guides

🌊 Tide tables

🛰️ Digital chart products

Together, these tools help navigators build a complete understanding of the waters they travel through.

The Mapworld Recommendation

A nautical chart is far more than a map.

It is a navigational tool built from decades of hydrographic surveying, maritime knowledge, and practical seamanship.

Whether you're planning a coastal passage, exploring a local estuary, fishing offshore, crossing Bass Strait, or preparing for an international cruising adventure, a quality chart provides something no GPS screen alone can offer:

Context.

It shows not only where you are—but what lies around you, beneath you, and ahead of you.

At Mapworld, we stock one of Australia's most comprehensive nautical collections, including official AUS charts, DPI inshore charts, Imray cruising charts, tide tables, marine navigation tools, and chart accessories. Every official chart is supplied with a focus on accuracy, current information, and practical use on the water, helping Australian mariners navigate with greater confidence wherever the coastline leads.

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