How to read your paper charts

Information on reading your paper chart, including the different elements of the chart title block and other important features.

About nautical charts

The nautical chart is the mariner's road map. Effectively using a chart helps you identify the best route to your destination and prevents accidents. By making frequent references to a chart during your travels, you can identify obstacles that you wouldn't see with your eyes alone. Obstacles such as rocks and sandbars can stop your boat in its wake and could harm:

you
your vessel
or the environment

Symbols, abbreviations and terms

The Canadian Chart 1 – Symbols, Abbreviations and Terms is a nautical publication containing explanations of the symbols, abbreviations and terms needed to interpret nautical charts and is published by the Canadian Hydrographic Service.

Member nations of the International Hydrographic Organization (IHO) produce Chart 1 using a common format. That common format consists of sections identified by letters and symbols, abbreviations or terms identified by a reference number.

For help using your chart, refer to the Schematic layout of a paper chart as seen in Canadian Chart 1 - Symbols, Abbreviations and Terms (free for download).

Title block

The first thing that you should read after purchasing your paper chart is the title block. It is often overlooked when referring to a chart, but contains many important elements that are needed when using your chart.

Seal (or Crest)

Most Hydrographic Offices print their seal on the chart, usually above the chart title.

General geographic area (regional identification)

The regional identification identifies the general area in which the chart is located.

Chart title (main title)

The main title identifies the specific geographic area being charted. Chart titles that are in terms of "from/to" defines the upstream direction.

Scale identification

We refer to the relationship between the size of the chart and the earth as 'natural scale'. For example, 1:15 000 means that 1 unit on the chart equals 15 000 units on the earth. The following are examples of different types and scales of charts and their uses.

Harbour charts are:
- large scale, 1:2 001 to 1:20 000
- used for navigation in harbours or intricate, hazardous, shoal-infested waters
Approach charts are:
- 1:20 001 to 1:50 000
- used for approaching coasts where a lot of detail is required
Coastal charts are:
- 1:50 001 to 1:150 000
- used in fisheries charts
- used to show continuous extensive coverage with sufficient inshore detail to make landfall sightings easy
General charts:
- 1:150 001 to 1:500 000
- used in fisheries charts
- give extensive offshore coverage with sufficient inshore detail to make landfall sightings easy
Overview or sailing charts are:
- 1:500 001 and smaller
- used for offshore navigation beyond sight of land

Projection identification

Chart projection is a method by which we represent a curved surface (the earth) on a flat piece of paper (the chart).

The Mercator projection is the most commonly used for nautical charts. It virtually reduces the shape and direction distortions that occur during the flattening process.

When boating it is essential to be able to recognize features by their shape, such as points of land or shapes of islands. You can compare these shapes to the charted features when attempting to determine your position.

Depths note

The depths note indicates what units are used for the depths on the chart. Charts have depths shown in feet and fathoms (1 fathom equals 6 feet) or metres and decimetres.

Eventually, all Canadian charts will show depths in metres.

An example of depths shown in meters and decimeters on a chart

Elevations note

The elevations note describes the datum used to show the elevation of structures and the clearance of bridges and overhead cables.

Use this note to determine if your boat has enough clearance to travel under the overhead cables and bridges.

Horizontal datum

The horizontal datum describes the starting point used for positioning objects on the surface of the earth. An explanation of horizontal datum charts is available in Canadian Chart 1 - Symbols, Abbreviations and Terms.

Sources note

The sources note identifies where data on the chart has come from and how old it is.

Symbol reference note

The symbol reference note is the last note in the title block. It refers you to the Canadian Chart 1 - Symbols, Abbreviations and Terms.

Bar scales

A bar scale is a graphic scale represented by a line or a bar that is subdivided into nautical:

feet
miles
metres

This bar is used for measuring distances on the chart.

Compass rose

One or more compass rose is shown on each chart in places that are selected for their use. Magnetic variation (example): 004 1/2°W 1985 (8'E) on the magnetic north arrow means the Magnetic Variation was 4 1/2° in 1985 with an annual change of 8'E (decreasing 8' annually).

Edition date and numbers

The edition note indicates the publication date by month, day, year and is located in the lower left-hand corner of the chart.

Elevation contours

Elevation contours are lines that connect points of equal elevation.

They're how we show the shape and slope of hills and mountains in graphic form to help you identify them on the chart. Once you identify them on the chart, you can identify your location on the water.

Hydrographs

We include hydrographs on charts for tidal and non-tidal waters. Hydrographs indicate the:

fluctuations in water level over a 1-year period
highest and lowest water level ever recorded for each month
amount of water to expect above chart datum during any month of the year

An example of a hydrograph for non-tidal waters.

Insets

We use insets when a particular area of the chart can't be represented with enough detail to be safely used by the mariner.

Objects of interest can't always be shown on a chart with a scale of 1:15 000, such as:

marinas
channels
yacht clubs
small islands

Place names

Your chart includes names of places of interest to mariners, such as:

cities
islands
points of land
towns

Publication note

The publication note (publisher's imprint) includes the date of the chart's original publication and is placed in the centre of the lower margin of the chart.

Date modified:: 2022-05-19

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