Understanding Contours

Once you start to head off trail, you must use all of your observation skills to keep track of your location. The shape of the ground can provide many clues to your location. On advanced courses, control features could be the top of a hill, on a spur, or in a re-entrant. To help provide a mental picture of the shape of the terrain to the orienteer, contour lines are used.

Contour lines are brown lines on a map to help illustrate the shape of the ground and changes in elevation. By definition, a contour line is a continuous line on a map that joins points of equal elevation throughout its length.   

Contours are normally drawn as continuous brown lines and are the standard method of showing relief on topographical as well as orienteering maps. 



Contour Interval

The vertical rise in elevation between adjacent contour lines is a fixed distance.  This is called the contour interval.  On most orienteering maps the contour interval is usually 5 meters.  However, on sprint orienteering maps or areas with very little elevation change, a contour interval of 2.5 meters can be used.  The contour interval on an orienteering map is always stated prominently somewhere in the marginal information, usually close to the title of the map and the scale bars.


Common Contour Features

Some common landforms that are easily recognizable in the terrain are hills , saddles, spurs and re-entrants. 

The steepness of slopes are often factors in route choice, so it is good to distinguish between gentle and steep slopes, which can be identified depending on how close the contours are. The closer together the contour lines, the steeper the terrain.

Look closely at the depression and you will see the use of slope lines. These small brown lines help identify in which direction the slope is dropping off.

Sometimes there are terrain features that are prominent but not big enough to span a contour. To show these, a form line is used. A form line appears as a broken contour line and may be open or closed. Look for an example of a small hill in the image above. Brown is also used to identify small point features such as knolls and pits and small linear features such as erosion gullies and earthbanks.

Reading contours and using these for navigation is a high level skill that needs a keen eye and constant practice. Let's see this in action. In these two videos produced by the South London Orienteers (SLOW), orienteers from the British Orienteering team will show you how to use large contours and intricate contours to help you decide your route choice.

Using Large Contours



Using Intricate Contours 



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