Lab 3a: ArcGIS and Projections

Having knowledge of your physical surroundings has always been important whether it is for economic, political, military or even basic survival purposes. Having an accessible, detailed and accurate representation of these physical surroundings is a continuing challenge even in modern times. The primary source of this problem stems from the fact that a sphere cannot be represented or transformed into a two dimensional object without distortions to the original object, such as distance, area and shapes. In order to address this projections are used to preserve specific characteristics of the sphere. A projection is a method of representing a sphere or an ellipsoid on a flat surface utilizing mathematical models, or originally using a light to project an image or shadow of the sphere onto a flat surface. This ability to create accurate two dimensional representations using projections is incredible valuable, seeing as carrying around a 3D dimensional model at all times is highly impractical. Even today with 3D or pseudo-3D digital models, time and resources are saved by using the appropriate flat projection and it seems doubtful that computer 3D modeling would have developed without the original techniques to make accurate 2D models.

There are an unlimited number of possible projections; however the most common types can be separated into three types: Conformal, Equidistant and Equal Area. Figure 1 shows two examples of Conformal projections, a type that focuses on preserving objects and shapes located on the globe. In both the Stereographic and Mercator projections angles are preserved, as seen by latitude and longitude maintaining intersections at right angles. Another type of projection, Equidistant, shown in Figure 2, attempts to maintain accurate distances between objects. The third main category of projections, because it is not focusing on distance or shapes, focuses on preserving the area of objects on the globe. Figure 3 demonstrates this as each 30 degree by 30 degree cell on the grid has approximately the same area.

Taking advantage of the strengths of each projection is dependent on the creator of the model and if done correctly can provide important benefits. As mentioned previously, there are immense advantages to having accurate spatial data in all areas of society, and in the modern era the necessity of having this data is growing. From a technical perspective, choosing and correctly utilizing a projection has benefits in the form of time and energy. If a sufficient 2D model is created time can be saved when it would have been used to create a physical or digital 3D model instead. However, also on a societal scale projections have allowed for increased ease of planning and operating from areas of marine charts that allow easier straight line navigation to projections that allow efficient planning of satellite orbits. Regardless of the purpose the benefits of choosing the appropriate projection for the task at hand should not be overlooked.

With this said, as projections are chosen for their benefits, one must also acknowledge their faults and the challenges they present. Referring back to the previous Figures, in each case where a feature or element of a sphere was preserved another component has significant distortion. In Figure 1 with Conformal projections as you get farther from the equator the area of each grid box increases, until Greenland is the size of Africa and Antarctica becomes an enormous disproportionately large landmass at the bottom of the map. Each projection has its own disadvantages, which is potentially problematic not only for users of the maps, if they are unaware of the extent of distortions and the implications that may have on their calculations using the map, but also with creators of maps. If incorrect projections are used, people working in GIS may unknowingly create incorrect data, if the projection they are using does not match up with the projections of their other data, or if they are using the wrong projection for their intended purpose. However projections are made, whether using modern day computing or existing as century old maps, their development and subsequent widespread use attempts to overcome the same fundamental problem that has always plagued geographers.