subject: Understanding Contours in the Map [print this page] Before proceeding with the topic, it is necessary to know what actually map is. Map is generally a geographical diagram or plan of an area or country. In other words, it is a visual representation of an area. A map is a way to represent on a two dimensional surface, any real location of an area, place or object.
Maps are grouped into two types: plan metric and topographic. The former maps are considered to be simple, flat plans, for instance, street maps. These are of no use to hill walkers. The latter on the other hand, show the shape of the land. They provide extensive close up detail about the area or place. Contours lines are used in these maps, these lines join the points of equal height together. Topographic maps unlike other maps are somehow considered to be three dimensional. These maps through contour lines shows the approximate shape of the area, for instance, if we talk about hills, it will show you where the ridges, plateaus, and cirques are. And also give you an idea about possible height, pointed or flat surface.
One main problem with reading contours in the map is to differentiate between spurs and valleys. The easiest way to deal with this problem is to look for a stream. If you find one going down to the middle of the contours, it must be a valley. But this does not mean that the absence of a stream represents the spur for not all the valleys have stream in them. Remember, contours lines are always marked at certain intervals on the map with the elevation above sea level. Different maps have different intervals length like Ordnance Survey Maps are marked every 50m on most of the Outdoor Leisure Maps, whereas its 75m on Harley's Map. The maps come in different formats. In some the heights are printed the right way up, in some it is upside down and in other it is on sideways. So you have to be clear enough that with the heights right way up, the ground slopes up towards the top, while for upside down, the grounds slope towards downward. Thicker lines are also often used to draw contour lines to make them prominent. Once you are able to deal with the heights, you will be able to know whether a map represents a ridge or a valley.
Like contour lines are marked at regular intervals to represent the height, contour lines are also draw at regular intervals on the map. On Ordnance Survey Map, they are drawn after every 10m and for Harley's the interval is of 15m. To understand the contour lines, it is important to have a clear knowledge about the intervals. Don't get confused by large scale or small scale maps. Although the interval is the same in both the maps but in smaller scale maps this interval seem closer to each other and eventually a slope look steeper than larger scale map. You need to understand these all features regarding the contours line to understand the map.
Understanding Contours in the Map
By: Tauqeer Ul Hassan
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