ocr: Look at the illustration opposite. The green half of the figure is a cross-section of a hill. The brown contour lines below show the same hill in plan view. Contours are drawn at regular intervals, often at 10 metres. So, for every 10 metre neight-increase (or decrease) on the ground, another contour needs to be drawn on the map. Notice that the slope is steeper when the contour lines are closer together.