Lab 5 - Projections

Map Projections

The distance between Washington D.C. and Kabul is approximately 6,936 miles.

The Conformal Projection: Mercator displays a distance of 6,865 miles between Washington D.C. and Kabul.

The Conformal Projection: Asia North Lambert Conformal Conic displays a distance of 6,800 miles between Washington D.C. and Kabul.

The Equidistant Projection: Equidistant Cylindrical displays a distance of 5,064 miles between Washington D.C. and Kabul.

The Equidistant Projection: Equidistant Conical displays a distance of 6,970 miles between Washington D.C. and Kabul.

The Equal Area Projection: Cylindrical Equal Area displays a distance of 10,192 miles between Washington D.C. and Kabul.

The Equal Area Projection: Asia North Albers Equal Area Conic displays a distance of 7,268 miles between Washington D.C. and Kabul.

Map projections are commonly used to reshape Earth’s three dimensional surface into a two dimensional image. This transition is mathematically calculated by altering the x, y, and z coordinate planes into x and y two dimensional space. The practicality of the two dimensional map projection is by far the most advantageous quality of ArcGIS map projections. The ability for users to be able to manipulate the characteristics of the map, and personalize such editing, allows for a more efficient and understandable geographical display of a designated region. Even though there are advantageous qualities to a map projection, it is still an abstraction of the three dimensional field, which induces distortions of the Earth’s shape, area, distance, or direction.

One disadvantage to the Conformal Projections is the fact that even though the map keeps the true shape by angles of highlighted features, such as continents, the projection displays inaccurate internal areas of the features. For example, the to conformal projections, Mercator and the Asia North Lambert Conformal Conic, alter the spatial equivalency of different countries. Greenland is shown to be much larger in comparison to Mexico, but in reality, these two countries are spatially equivalent. The conical arrangement of the Asia North Lambert Conformal Conic projection allows for angular accuracy to be upheld, but sacrifices the visual comparison area within different features.

Another disadvantage of map projections is seen specifically in planar conical projections. Planar conical projections are the best displays of global regions, which do not require a high degree of positional or spatial accuracy. However, either the area or shapes of distinguished features are highly skewed. The Asia North Albers Equal Area Conic shows the distortion seen in planar conical projections. The countries located around the central point are proportionally represented to one another, but the features farther from the central point are spatially skewed. Planar conical projections are efficient in representing an area centered on the line parallel to the central point of the conical shape, but distortion of the area or shape of various features is present when distance between the central line and the feature increases.

Map projections, when used correctly and displayed efficiently, are appealing and intriguing tools for spatially representing the global distribution of featured elements. Even though the accuracy of shape, area, direction, and distance may be sacrificed when manipulating the Earth’s three dimensional surface into a two dimensional surface, it is much more practical and easier to display geographical features on a two dimensional surface rather than a three dimensional surface.