Lab 5: Projections in ArcGIS

Map projections:

Conformal:

Equidistant:

Equal Area:

As we know, our earth is a slightly irregular ellipsoid. Since it is not convenient to map in a three-dimensional space, it is important to put the surface of the earth onto a two-dimensional plane. Also, because the earth surface is a curved surface that cannot be flattened, we introduce many different map projections to preserve some of the features of the earth surface for diverse uses. In ArcMap, there are a lot of map projections for us to choose. By making these map projections, I had a further understanding about conformal, equal-distant and equal-area map projections, and I also perceived the strengths and pitfalls of different map projections.

First of all, it is quite interesting to see the same map in different map projections. Although I cannot imagine what the Bonne map projection with a shape of heart can be used for (but I believe it is useful for some purposes), it's just quite fun to look at it. However, in spite of the beautiful shapes, the distortions of the maps are also easy to be observed. In Mercator map projection, the area of Antarctica is much bigger than its actual size. Also, in Lambert Conformal Conic map projection, Australia is almost as large as Eurasia which is impossible, and I could not even see where Antarctica is in that map. 

In this lab assignment, we also compared the distance from Washington D.C. to Kabul. We could see that the distortions in different map projections do influences the accuracy of the maps. On the internet, I found the actual distance between Washington D.C. and Kabul is about 7000 miles, which has a very big deviation to the data I measured on some of the map projections. I think the distortions may be neglected in a small area, but it should be definitely taken into consideration when we are making measurements or projections in a large area of the earth.

It is true that each kind of map projections has its strengths and pitfalls, and it seems that there is no "perfect" map projection. However, when we are making a map, we can simply choose the most suitable map projection to use. For example, when we are making maps reflecting features like population density or administrative division which requires the accuracy of areas, Equal Area map projections should be the most suitable. Also, if we want to have a direct perception of the world, a conformal map projection which shows the longitudes and latitudes intersect at right tangle should be a good choice. 

To sum up, when we are making maps, we just need to make best use of the advantages of different map projections for different purposes. Since we have so many different map projections to choose from, we will always be able to find a most suitable projection to use. What's more, since maps are playing a more and more important part in our daily life, and we need different maps for different purposes, I think there will be other map projections invented to adapt to the demand.