How to read contour lines on topographic maps.
Imaginary lines called contours are an important way of showing the rise and fall of the land on a map. Contour lines show all the places that are the same height above sea level. Contours also tell us about the slope of the land. On a steep slope, the lines are close together. On a more gentle slope, they are farther apart. If there are no contour lines, the land is almost flat.
Hikers study the contour lines on maps to find out whether hills will be easy or difficult to climb. Once you get the hang of it you can also visualise gullys, cliffs, ridges, spurs and many other geographical features.
The map to the right clearly details the contour lines of the hill in the image. The water in this map is at sea level and the hill in the foreground rises up reasonably steadily to over 400m. You can also pick out the forested areas in the image on the map.
Representations of Height
Height without reference to shape is shown by fixing the height above sea level at selected points. Three common types are described below in order of accuracy.
Theses are the most precise heights and are usually a permanent mark cut into a stone, built into a wall or on the side of a triangular pillar. The height given is the height of the mark and not the level of the ground.
These are usually shown on maps and are defined on the ground normally by a mark in a concrete block underneath a survey beacon.
These are less accurate heights and are without a definite mark on the ground. They are selected to indicate the height of the ground at points such as the tops of hills. Their accuracy varies, but its as accurate as the contours.
To help you picture the land, maps are shaded as if they were lit from the north-west. Beware of reversing the effect by viewing a map upside down. The darker shaded side of slopes will on the south- eastern facing slopes.
Try you hand at matching the following