Contours may resemble Form lines , but are actual measurements rather than points of reference.
Relief is shown by lines drawn to indicate a conception of the shape of the terrain.
Form lines differ from Contours in that they are not measurements, merely representations. Relief is shown by different colors applied to the area between contour lines. Relief is shown by short lines, following the direction of maximum slope. Also known as Hill shading . Relief is indicated numerically, indicating measured or charted depth in water.