Sailing is a discipline based on a foundation of knowledge and there's no maritime skill that's really more valuable than the ability to navigate your boat safely and accurately through waters both familiar and strange.

Getting to grips with nautical charts is an important asset to any new seafarer and familiarising yourself to the basics - from chart symbols to water depths, obstructions to buoys - will put you in good stead for developing the keen mind of a seasoned navigator.

To help you out, allow Seachest to shed some light on a few key aspects of reading nautical charts, making you a better sailor when you revisit the open ocean.

The General Information Block

Your centre of knowledge and the first place you look on the chart - in the general information block you'll find the title of the chart, the name of the waterway or sea that's suitable to navigate as well as water depth measurements, or soundings, represented in either feet or fathoms.

In the block notes, you'll also find explanations on chart abbreviations, warning information, anchorage points and everything else needed to make sure you make safe passage.

There are typically 4 types of nautical chart : sailing charts, coastal charts, harbour charts and small craft (leisure) charts. All of these charts are important as they give a sailor different scales, ratios and information, depending on the distance of the sail and where you're travelling to:

#1. Sailing Charts are really only used for long-distance sailing and navigating the open ocean.

#2. Coastal or general charts are great for sailing and navigating close to land - honing in on bays, harbours and other inland waterways.

#3. Harbour charts are great for detailing smaller waterways, anchorages and of course harbours.

#4. Small Craft or Leisure Charts are great for hobbyists and weekend sailors, typically printed in a practical and economical way for easy storage in your cabin.

The Compass Rose

A Compass Rose or Wind Rose is an important feature for plotting a course and is used to ascertaining true or magnetic bearings of north, south, east and west. Typically the 'true' orientation is displayed on the outside of the rose while magnetic bearings are found on the inside.

A modern compass rose typically has 8 principal winds - or points of the compass.

Latitude & Longitude

You can find where you are using the lines of latitude and longitude located vertically and horizontally on the chart. Latitude = vertical, signifying north and south, whereas longitude = horizontal, signifying east and west.

The zero points for latitude is the equator and the zero point for longitude is the Prime Meridian (Greenwich Meridian).

Soundings & Fathom Curves

What do the numbers mean on nautical charts?

Of all the various elements of a nautical chart, knowing the depth and understanding the underwater geography is probably the most fundamental. On a sea chart you'll find numbers and colour coding, as well as wavy fathom curves that help you understand the seabed idiosyncrasies - the numbers themselves actually indicate water depth measurements or soundings, displaying the low tide depth area.

Bear in mind that soundings shown in white flag up deep water whereas shallow water is shown in blue.

The Distant Scale

Found near the top or bottom of a nautical chart, the distance scale is designed to help you measure the distance of a certain drawn course on a chart in miles, metres or yards. However, the latitude and longitude will also help you to determine distance as well.

Post By Ed Mason