Aiming-Off

Your compass is a very valuable aid to direction.  However, as most orienteers will experience, following a compass bearing through rough terrain or for long distances can usually result in some deviation on your bearing. 

Some orienteers may have noticed a tendency to generally err to one side more than the other.  This may be caused by a slightly uneven stride or a habit to move around obstacles on one side more than the other. This is not uncommon for most navigators. Even expert orienteers can get thrown off their bearing if travelling quickly through rough terrain. 

Your compass is still your best tool to help keep your direction, so it is good to learn additional strategies to mitigate possible limitations in your accuracy.  In other words, expect that you will have some tendency to deviate and take this into account when you need to follow a compass bearing.

Aiming-Off

Let's look at a quick example. You are located at Control 7 and are planning your approach to Control 8.  Control 8 is located on a boulder near a small stream, a long linear feature.  There are no other features nearby to help reference you.

You could head direct for Control 8 by shooting a compass bearing from your location. The stream is a great catching feature, however, there is a risk. What happens if you deviate from your bearing and hit the river at a different spot then the location of the control?  Uncertain which direction you may have deviated, you must make a choice to turn left or right when you reach the stream.  If you happen to turn the wrong direction, you run the risk of compounding your error by running in the wrong direction away from the control.

This is a situation where aiming-off can be used effectively. By deliberately aiming to one side of the control you can intentionally ending up on one side of your target.  Now the decision to turn left or right is easy.  In this example, you choose to deliberately aim right of the control, when you reach the stream you are confident which side of the control you are on, and therefore, turn left to handrail along the stream and find Control 8 quickly and smoothly.

Let's see this in action!

Here is a quick explanation and demonstration of aiming off as shown by Sport Scotland (Glenmore Lodge).

 

And, here is also another great video from the South London Orienteers (SLOW) that will help show you a number of different situations where aiming-off can be used effectively.

 

 

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