Relief is the representation of all portions of the earth above the sea which have a three-dimensional form, sometimes referred to as ‘the lay of the land.’ Early cartographers were unable to symbolize relief accurately due to lack of familiarity with land forms. When surveying became a precise science, this shortcoming no longer prevailed and it then became feasible to portrait the earth’s terrain accurately on a map. Methods of showing topography have varied over the centuries. During the 16th and 17th centuries, mountains were show in profile, sometimes called ‘molehill’ style. Later, hachuring was used to delineate the terrain effectively. With better technology in the 19th and 20th centuries, contouring, hyposometric, shaded relief, and pictorial/land form styles became feasible, providing map readers new realms of accuracy and detail.
Profile (molehill) relief was the method used by cartographers of the 16th and 17th centuries. Mountains were shown in profile and placed to show where mountain ranges existed. This method could only indicate the location of mountains but could not accurately show relief in ‘plan’ as modern maps do.
Hachures are short lines drawn down the slope in the direction of the steepest gradient; conventionally, they are drawn more closely together where the slope is steeper, and can be made heavier on the southeast sides of land forms to give an increased appearance of relief. The chief disadvantages of hachuring are (1) the lack of absolute information for which numerous spot-heights have to be inserted; (2) the difficulty of drawing hachures in the field; and (3) the problem of distinguishing directions of slope. The chief advantage is that it enables minor but important details, lost on a contour map within the contour interval, to be brought out; and sometimes it can show country of striking relief in a very dramatic manner.
Contours or contour lines are lines of constant elevation drawn around land forms at predetermined intervals of height above mean sea level. A contour can be thought of as an imaginary shoreline or as a bathtub ring. Contours provide both measurable information and a picture of the land forms.
Hypsometric shading, also called layer-tinting, is the use of tints of different colors or shades within one color to distinguish different bands of altitude so that low, middle and high ground is apparent at a glance. This is not an effective method of revealing land forms and is in a sense misleading because a single shade between 100- and 200-foot contours indicates a uniform level instead of a progressive change of altitude.
Relief-shading, also called hill-shading, attempts to give the effect of a relief model. This method uses various tones to resemble the shadows that would be created by land forms if they were illuminated from the northwest. The steeper the slope the darker the show, while the ridge crests, plateaus, valley bottoms and plains remain light.
Pictorial/land form relief is an attempt to combine accurate plan-view of relief with a pictorial side-view. It is somewhat similar in approach to the ancient molehill method in being pictorial, usually showing relief at an oblique angle. Unlike old maps, accurate placement of features enables the modern renderer to present a much truer appearance to the relief.
