Lab 1 Map Projections

Map Projections

Our beloved Mother Earth can be displayed as a flat map through a variety of projections. These different projections transform Earth’s spherical surface to a plane or flat medium (i.e. paper or computer screen). A map projection is “a systematic arrangement of parallels and meridians on a plane representing the geographic coordinate system.” (Chang, pg.24) Map projections cannot transform Earth’s three-dimensional curved surface to a two-dimensional surface without a relative degree of distortion in true shape, area, distance and/or direction. At the same time, a flat map would be non-existent without a map projection because a sphere cannot be laid flat over a plane without a certain level of the above mentioned distortions. Even a globe is relatively distorted due to the actual shape of the Earth being an oblate spheroid, not a sphere. Although map projections cannot rival the accuracy of a globe, map projections offer a variety of advantages such as portability, range of scale, range of view and affordability. For these reasons, map projections are widely used and are imperative to spatially depict geographic references on a flat medium.

Conformal map projections preserve angles locally and maintain shape. Every parallel intersects the meridian at a 90 degree angle. Mercator and Gall Stereographic are two examples of conformal map projections. In the Mercator map, the Rhumb lines are represented by straight lines making the poles look larger distorting size increasingly further away from the equator. Notice the area of Antarctica is equal to or greater than the total area of all other continents combined. The Gall Stereographic map preserves the shape of circles and distorting area, specifically near the projection point. For obvious visual reasons, conformal map projections are not ideal for world maps.

Equal-area map projections preserve area; all the features on the globe are kept to scale. Bonne and Mollweide are two examples of equal-area map projections. In these maps the features are kept to scale at the cost of shape. The Bonne map projection maintains accurate area along the central meridian and standard latitude. The Mollweide map projection sacrifices fidelity of angle and shape in favor of accurate depiction of area. Mollweide projections are most commonly used for global maps.

Equidistant map projections preserve distance from a point or line at the meridians and standard parallels at the expense of area and shape. Cylindrical and conic equidistant map projections were used as examples. Cylindrical equidistant projections are the simplest map graticule dating back to approximately 200 B.C. and was used for navigation until contemporary times. It is often used for topographic maps. Equidistant conic projections maintain constant parallel spacing and are acceptable for mapping temperate nations.