Navigation - Slope Aspect and Direction of Linear Features
Slope Aspect
Using slope aspect can be a very useful tool to help you relocate. In its simplest form just use the points of the compass - north, east, south and west - to work out which direction the slope you are on is facing and then look at the map to find the slope which faces this way.
Slope aspect can be used more precisely by taking a bearing of the direction in which the slope faces.
Let's imagine we have become disorientated somewhere within the
area shown by the map
[Permission by
Harvey Maps]
| We know we haven't gone far and we're somewhere within
this circle of map [Permission by Harvey Maps] |
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| We've taken a bearing of the direction in which the
slope we are on drops away. There can be slopes of very different directions all located within a small area. The task is to find out which slope you are on [Permission by Harvey Maps] |
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Let's assume the bearing we took of the slope on the ground was 30° [Permission by Harvey Maps] |
| Place the compass on the map in the rough area where you
know you are. You have already got 30° set on the compass
because you've just taken the bearing of the slope
direction. Without moving the compass housing, turn the
whole baseplate until the parallel lines in the compass
housing line up with the grid lines on the map [Permission by Harvey Maps] |
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Move the compass around the area you're in until the
edge of the baseplate is at right angles to the contours of
the slope you think you are on. Make sure you keep the
bearing set on the compass [Permission by Harvey Maps] |
| Make sure you line up the parallel lines in the compass
housing with the grid lines. Only move the compass baseplate,
don't turn the compass housing because this will change the
bearing you have taken [Permission by Harvey Maps] |
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This is slope which you have identified. Usually there
will only be one slope in the area you are in which faces a
particular direction and so this gives you some quality
information about your likely location [Permission by Harvey Maps] |
To be really accurate you can subtract the magnetic variation from the bearing you took on the ground but this isn't strictly necessary because the bearing you have taken is only approximate anyway.
- This page reproduced with the kind permission of the Mountaineering Council of Scotland (MCofS). They run a number of Mountain safety courses, Seminars and Lectures. You can join the MCofS here.