Three Named Map Projections - Essay Example

GIS Essay – Three d Map Projections Essay Topic Compare and contrast 3 different d map projections to illustrate how they differ in representation earths surface and their purpose in Cartography. Introduction A map can be defined as a document representing an area visually. In other words, a map highlights the relationship presents between different elements, such as objects and regions, present in the area that it represents. A map can also be defined as a representation of whole or a portion of Earth on a levelled surface to a specific scale. Maps gained their utility from the fact that they were much easier to carry, utilize as well as store then globes, and significantly eased the development of representation on different scales that were both larger and smaller than those possible on globes (Government of Minitoba, 2011). However, while maps allowed for such enhancement, they also introduced several complexities in the art of map drawing (cartography). One of the major problems that were faced by cartographers was the accurate representation of an ellipsoid object on a flat mapping surface. As a result of research on this topic, map projections were introduced. Map projections are methods which are used to represent whole or part of a sphere or a three-dimensional body on to a planar surface (Riesterer, 2008). In terms of earth mapping, map projections were initially used to transfer the features of a globe , such as coordinates and outlines of land areas on to a piece of map. Initially, light was used to "project" a wire globe onto a flat surface, however, as the research progressed these methods were replaced with more scientific method involving mathematical equations and use of computers (Government of Minitoba, 2011). There are basically three major types of projections, cylindrical, planar and conic which are based on the shape of the flat surface (usually paper) on to which the sphere is projected. A cylindrical projection is one in which lines of longitudes are mapped to equidistant vertical lines while rings of latitude are mapped on to horizontal lines. In a planar projection, the directions from the central point are preserved, and great circles through the central points are shown by straight lines on the map. In the conical projection, the lines of longitudes are projected on to a conical surface joining at the apex of the cone. The lines of latitudes are drawn on the cone as rings. This cone is then cut along any longitude line to obtain the conical projection (Riesterer, 2008). All subsequent developments of map project use these three map projections as their basis. An aspect which is considering during the projection process is the aspect of the shape. The aspect of the map describes how the surface is oriented in relation to the sphere or globe. The surface can be normal, transverse or oblique or can also be tangent or secant to the globe. A projection may also be affected by the approximation that is used to measure the shape of the Earth. Some map projection use the approximation of Earth as a sphere, even though Earth is actually and ellipsoid. The use of sphere vs. ellipsoid for Earth approximation is decided by quantifying the advantages and disadvantages of each approximation method. Though a more accurate model of Earth, called geoid, exists however it is no used in mapping due to the significant amount of complexities involved in its use (Government of Minitoba, 2011). Despite the fact that more and more accurate methods are being developed as the research in the field of cartography has progressed, it is important to understand that a globe is the only true representation of the Earths sphere and all attempts made to project it on to a flat surface introduce some sort of distortion in one way or the other. This distortion can be understood from the example of peeling of an orange. Any attempt made to straighten the peel will result in creation of tear and wrinkles on the surface of the peel creating distortion (Government of Minitoba, 2011). When considering maps, distortion involves change in characteristics of latitudes and longitudes, distances between different objects and places, direction, size of areas as well as the shapes of features present on the map (Riesterer, 2008). There is also a direct relationship between the amount of distortion found on the map and the size of area that the map represents. It is important for a map user to be aware of all types of distortions that can be found on a map in order to minimize the influence on the distortion on how the map is perceived (Government of Minitoba, 2011). Map projections have often been named after the people who first developed them, after the method employed in the projection or using the combination of both. Traditionally, all maps and atlases specify the type of projection used to create them. There are a number of named an un-named projection in used throughout the world, however, three of the well known map projections are Mercator Projection, Peters Projection and Robinson Projection (Government of Minitoba, 2011). Mercator Projection Mercator projection was first developed in 1569 by Belgian geographer and cartographer Gerardus Mercator. It is a cylindrical projection in which both latitude and longitude lines appear parallel and perpendicular to each other. One of the drawback of using the Mercator projection is that although it represent the shapes of the features found on the map quite accurately, however, the distances between different elements as well as areas have a great deal of distortion in them. This distortion particularly becomes significant when higher latitudes are considered. This results in a map which is accurate in its area and distance representation when considering areas around equator, but gets distorted more and more as areas closer to poles are considered. The distortion in higher latitude areas has also led to the criticism on its used in classrooms, particularly in countries lying in the tropical region as these countries are shown as very small as compared to the countries lying near the polar region. This was particularly troubling issue in the colonial era, as countries lying closer to the poles (such as Britain and France) were ruling much of the world as the use of Mercator projection unfairly allowed them to emphasize their dominance on a world map (Government of Minitoba, 2011). On the other hand, soon after its introduction, the Mercator projection also became the standard projection used for nautical purposes due to its facilitation in representing lines of constant course as straight segments (ESRI, 2011). The conformity as well as the use of constant bearing made this projection unique for marine purposes as these properties were important to the type of routes used by ship at that time, which made use of compasses for their navigation (Government of Minitoba, 2011). However, due to its distortion, cartographers agree that the Mercator projection cannot be used for general reference maps and as a result the Mercator projection is no longer used by modern atlases for world maps. Mercator himself used a different type of projection to overcome this distortion (Snyder, 1997). Peters Projection The Peters projection, also known as Gall-Peters projection, is a cylindrical projection first developed by the German historian Dr Arno Peters and British clergyman James Gall in 1973. They developed this projection in order to overcome the inaccurate representation of countries by the Mercator projection. This projection utilizes the concept of equal-area map which shows areas more precisely. Although the Earth grid used in the Peters projection is very similar to that used in the Mercator projection, however, unlike the Mercator projection, the distance between the lines of latitude does not increase as the map is read from equator toward poles. This greatly reduces the area distortion which was present in the Mercator projection. Due to this accurate representation, it has also received appreciation from organization working for the development of third world countries such as the United Nations who believe that the accurate representation of the world by Peters projection actually provide great support to the development cause of third world countries as development resources could be accurately allocated (Government of Minitoba, 2011). Despite its significant improvement over the Mercator projection, the Peters projection is also not without its drawbacks and has received fair amount of criticism for this. One of the major flaws of the projection that was highly criticized is its inability to accurately show the shape of the continents. Due to the distortion, many of the continents appear longer as well as thinner then they actually are when projected using the Peters projection (Government of Minitoba, 2011). Furthermore, the Peters projection was falsely promoted to be the only area accurate map projection while the literature suggested that there were considerable number of proposed projection techniques already by that time. Further exploration of the Peters projection by researchers also showed that it suffered from extreme distortion along the Polar Regions which was typical of any cylindrical projection (Snyder, 1997). As a result, the Peters projection did not receive a wide acceptance and is rarely used in modern cartography (Government of Minitoba, 2011). Robinson Projection The Robinson Projection was introduced by Profession Arthur Robinson in 1963. By creating this projection, Prof. Robinson attempted to overcome the problem of creating the image of whole globe on a flat surface thus creating a visually appealing map which showed the entire world on a single map. (Rand McNally, 2011) The Robinson projection is neither a fully equal area nor a conformal projection, but is a compromise between the two in order to keep the distortions introduced by both types to a minimum. The Robinson projection shows world as an oval, with lines of longitudes curving gently and do not converge toward a point, hence, the poles appear to be straight lines instead of points on the projection. The lines of latitude are drawn as straight lines (Government of Minitoba, 2011). The projection was developed as a response to the request of Rand McNally, a major map and atlas publishing company, who wanted to use a projection which made the maps in its publications more visually appealing (Rand McNally, 2011). This projection is still used by Rand McNally, however, has also been used by National Geographic Society for many of its maps (Government of Minitoba, 2011). Despite its significant acceptance in the world of cartography, the Robinson projection also contains distortion. Due to the fact that poles are represented as lines rather then points, extremely distortion is present on the extremities of the map. However, this distortion significantly reduces as a move is made toward equatorial regions. The straight latitude parallel also introduces angular distortion at high altitude. Conclusion One of major issues in cartography is the accurate representation of earth, in a flat surface. For this purpose map projections are used. However, the transformation of spherical elements onto a flat surface introduces distortion. Among the widely known map projections are the Mercator, the Peters and the Robinson Projections. The Mercator projection was developed in 1569 by Gerardus Mercator. This projection allowed for the use of constant bearing in the map which was the most popular method used by ships at sea at the time. However, this projection has the drawback of introduction of distortion in Polar Regions. As a result, countries near the equatorial regions were shown to be smaller then those situated on higher latitudes. The Peters projection attempted to solve the distortion problem present in the Mercator projection. This projection used the equal-area map techniques which allowed for accurate representation of the size of the countries; however, the Peters projection introduced distortion in the shapes of the continent which appeared to be longer and thinner than in reality. The Robinson projection was developed in 1963 by Professor Arthur Robinson. It was developed as response to request by Rand McNally publishing company in order to make their published map more visually appealing. Although map developed using this project also suffered from distortion in the polar region, however, it fulfilled the requirement of Rand McNally when it was published and is still in use by the company. List of References ESRI. 2011. Understanding Map Projections. ESRI Website [online]. Available from . Access date 19 March 2011. Government of Minitoba. 2011. Map Projections. Govertment of Minitoba Website [online]. Available from . Access date 19 March 2011. Rand McNally. 2011. About the Robinson Projection. Rand McNally Website [online]. Available from . Access date 19 March 2011. Riesterer, J. 2008. Introduction to Topographic Maps. Department of GeoSicences, Idaho State University Website [online]. Available from . Access date 19 March 2011. Snyder, J. 1997. Flattening the earth:Two thousand years of map projections. University of Chicago Press. Read More