Map reading As stated earlier, when interpreting any map do not place too much faith on man-made structures. The basic surface of the land is unlikely to change in your lifetime but man's works vanish. The most obvious natural features are ranges and rivers. The ranges may be steep or sloping. Their gradients are shown by countour lines or hatching. Contour lines are imaginary lines parallel in height and with equal height separating one line from the next. By correctly reading these lines you can tell whether a hill is concave or convex in its slope. Not all contour lines carry a height indicator. Sometimes they are marked in 'steps' of 100 metres, but if slopes are very steep more indicators are given. The crest of a ridge or a prominent landform is usually given its exact height. Position on a map is always given by map reference num-
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Part of a contour map. The bottom diagram shows a cross section ofthe line A to B.
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