Even though all the lines look similar at first, they are describing very different landscape features. The below picture shows how contour lines can be used on maps to describe different landscapes. Hill shading, such as on this OS Road map, can make visualising hills much easier but can also obscure features Identifying features However, for activities where this is less critical (such as driving or road cycling) using a map with hill shading instead of contours can be a good choice. The biggest problem with hill shading is that it tends to obscure or replace the contour lines, making it harder to work out accurate height data. Some map styles make this much easier for you by using hill shading, drawing shadows to create a 3D effect. The steams going to the reservoir and the lack of tree cover make is easy to see this is a peak on the left with a steep valley to the right. You will also notice all the numbers on countours are aligned with the top of the number uphill - meaning you can see slope direction without having to actually read the numbers. If you are an area near the tree line you can also easily see the difference between bare hill tops and valleys with distinctive green shading. One really obvious way is that streams are usually at the bottom of valleys, not on ridges, and tend to get larger as they go downslope. However, this can make it easy to read it in reverse - valleys looking like ridges, or hills like dips. In crowded areas the numbers can be quite a long way from the feature you are trying to view, and trying to find and read the tiny writing can be a pain, especially in poor weather. Ideally you don't want to actually read all the contour lines labels to understand the terrain. As the water level drops it would leave a line every 10 metres on the landscape. One way to teach it is to imagine the contour lines as high tide lines left by the sea. Some people find visualisation very easy, while others find it considerably harder, but almost everyone can do it with practice. Since natural features don’t change as quickly or easily as their man-made counterparts, being able to use them to navigate is essential.īeing able to visualise the contours easily gives you many more points that can be used for triangulation, as you can use otherwise unmarked hill crests, the line of a hillside or the drop into a valley.īeing able to picture contour lines on a flat map lets you 'see' terrain It’s also possible a man-made feature, such as a log cabin, can be added or removed from the landscape. In remote and difficult terrain man-made features can often be rare. The map key will tell you the contour interval used. For most OS maps it is normally 10 metres, but it can be 5 metres in flatter areas. ![]() The height difference between separate contour lines depends on the map being used. In brief, a contour line is drawn between points of equal height, so any single contour line will be at the same height all the way along its length. We'll assume you're already comfortable understanding how contours printed on a map represent the real world - if not have a quick look at our beginners guide to contours first.
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