Contour Lines: Types and Importance in Navigation

contour lines

Invented in the late 18th century, contour lines are the curves on the map that join the points situated on the same altitude, above the sea level. It also shows you the topographical features like heights, depths and slopes of the area during navigation.

Types of contour lines used in navigation

There are few distinct shapes of map lines. Here we explain the common types of contour line formations that will help in understanding the topographic map quickly.

Peak Ring

The peak ring represents the highest elevation of the area, and is the innermost ring located at the centre of several contour loops.


When you observe two or more lines until they disappear and form a single line, they locate a cliff. However, sometimes one can’t depict a cliff as the contour interval does not change.

Depression ring

The innermost ring may also sometimes represent the lowest elevation of the area. To distinguish it with a peak ring there will be a small tick mark at the innermost ring which points towards the centre known as “Hachures”.


When you see a V or U shaped contour line, it’s probably a stream or a valley. However, rivers are represented by the blue lines that run through the V-shaped lines’ centre.

One can also detect the direction in which rivers are flowing. If a river is flowing downhill, then the V shape map lines will point it in the opposite direction. It is also called the “Rule of V’s”.


Ridges are the elongated peaks that do not have a fine point and they are represented by the big oval lines instead of closed inner circles.


Between the two higher points of altitude, the low lying area is called Saddle. They are represented as hourglass-shaped lines within two concentric circles.


Ledges are the flat areas on the side of the mountains represented by U shaped lines pointing away from the peak.

How to read contour lines?

Topographic maps give you a general idea of the area in which you are navigating but to understand the landscape better, know that there are three kinds of contour lines used:

Index lines

These are the thickest lines labelled with a number and are useful for knowing the landscape’s elevation above the sea level.

Intermediate lines

These are the thinner lines which are not labelled and it lies between two index lines. Intermediate lines usually appear as five consecutive lines within two index lines.

Supplementary lines

For representing the flatter terrain, dotted lines are used known as supplementary lines.

To read lines, one should understand the contour intervals, usually located as a map key at the map’s centre bottom. The contour intervals help you determine the elevation change so that you can easily understand the landscape of the navigated area.

Uses of contour lines in navigation

Understanding map lines are essential for safe navigation in various landscapes. With the lines’ help, you can get a 3-D image of different landforms like valleys, peaks, cliffs and ridges and find your way accordingly. Some of the applications of contour while navigating are:

1. Map Reading

The better you understand map lines, the more efficiently you will be able to read the map. Which ultimately eases the navigation on your outdoor adventure.

2. Visualizing Terrain and landscapes

Whether the landscape is hilly, plain or plateau, contour lines give you all the information on various terrain in a particular area.

3. Working on slopes

The lines on a map help you find the type and steepness of the slopes which helps in planning navigation stages. Working on slopes also assists you by allowing you to estimate the time needed for navigation.

4. Finding way

To find a perfect way, one should use the map lines to provide you with the easiest, quickest and safest route. This process is also called “contouring”.

5. Finding your location

One can find his accurate location with the help of the compass and the map’s line by learning the navigation skill known as triangulation

Final words

Learning how to read contour lines is very important, particularly during navigation. It will help you to improve your map reading skills, open your eyes to new adventures and ensure you do all that in a safe way.