A feature is a distinguishable point on a map. It is either a small point such as a gate, which can be used as an attack point or it can be as big as the summit of a mountain which you can use for a resection bearing.
As given in the examples, features can be either man made or natural. Both are just as good as each other to use in navigation.
Key features you’ll commonly see on the hill:
Mountain top- This is the highest point of the hill or mountain. You’ll notice it is marked by the smallest circle (contour line) and the height will also always be marked.
Saddle- will look similar to an hour glass in shape. The hill will visibly dip slightly and then regain to a similar height.
Valley-A valley will either be U shaped or V shaped but either way you’ll see the contour lines decreasing on each side, usually quite steeply.
A linear feature is a feature that has a continuous edge. For example, a wall, this is a really helpful tool in navigation as you can use it to handrail. Hand railing is when you use a feature as guide, like a handrail to reach a certain attack point. For example, if you know a wall connects to a path you want to reach, you can use the wall as a hand rail keeping it to one side. As long as you keep the wall to your side you know you are on the right path.
Looking at the shape of contour lines and translating this to the ground is a very useful navigation technique. Trying to spot each spur, indent, valley or even change in the gradient of the slope will help you to be able to pinpoint exactly where you are on the map. Just remember that no two mountains are the same in shape so a confident navigator will be able to place each mountain from the map, to the ground. Having the ability to do this will help with other skills such as map orientation, resections and night navigation.
A contour line will show the difference in height of the land. The space between each contour line determines the angle of the slope, so the closer the contour lines are together, the steeper the gradient of the hill and vice versa. This is an important thing to remember when planning a route up the hill, as you do not to be walking up the steepest part, when there could be a much easier alternative option. In addition, it will also really help if you look at the type of land you’ll be covering. For example, you may notice a crag marked on the map with the contour lines close together. This would be a route to avoid. On the other hand, you may see on the other side of the mountain is a gentle grass covered slope with the contour lines far apart. This would be the better route to follow up the mountain. If you are unsure of what type of ground you are looking at, go straight to the key on the side of the map. It will tell you how each feature is represented.
When using an OS 1:25000 map, it’s helpful to know:
- Each contour line represents an increase or decrease in 10m. A top tip, to know if the height is increasing the number on the contour will be facing upwards. If, however the number is upside down, facing downwards, the slope is going down in height.
- Every fifth contour line is called and Index contour and represents a 50m change in height. It is clearly distinguishable from the other contour lines as it has a much thicker line
- The height shown is the height from sea level.
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