Equidistant maps preserve the accurate distance from a certain point. The Plate Carree map is an equirectangular projection based around the equator. Lots of distortions are introduced as a result, and it is neither equidistant nor conformal. Thus, it makes for a poor navigational map, but its simple presentation makes it the standard for thematic mapping and computer based applications that process global maps. The sinusoidal map maintains distance along parallels. There is no distortion at the equator or central meridian. The distance between two points is the distance from one point to another between the two parallels. This map is also equal area. Equidistant maps are effective tools for plotting distance between two points, but their distortions makes them hard to read and creates illusions of inaccurate proportions and size.
Equal-area map projections are tools used to show area based relationships. This is important for thematic maps such as population density, amount of forest cover, or desertification. The cost usually is that equal-area maps are rarely equidistant. The Hammer-Aitoff projection was developed by some dude named Hammer and inspired by the Aitoff projection. It maintains equal area while using curved parallels. The Bonne projection is a pseudoconical projection where the latitudes are concentric circular arcs. Although equal-area projections are very practical for certain applications, they are not as essential for day-to-day needs like navigation. Also, they have extreme distortion of distance and appearance, such as with the Bonne projection, which makes them just no fun to look at. I mean, seriously, what's going on there?
Conformal maps preserve angles and logically, are most often used for navigation. The coolest part of these maps is that they are usually flat and rectangular! Hooray. This makes them very easy to read and understand. The greatest drawback? The distortion of area. As seen in the mercator projection, Greenland is as large as Africa. While the Greenlandians may want to perpetuate this idea to have more delegates at the UN, this is simply not true. The Mercator projection (cylindrical projection) has increasing distortion the farther from the equator you go, and the distortion becomes infinite at the poles. (If only Antartica were that large. There would be so many more penguins. And lord knows I have a flightless bird fetish.) However, through use of rhumb lines, navigation is very easy and local area is still preserved. Likewise, the stereographic (I know, this is the "gall" version, but Lindsay said it was ok) projection is conformal, projecting the spherical shape of the Earth onto a plane. It preserves angles at the price of area and distance. It is mainly used for complex mathematical analysis that I do not understand and have no intention of understanding, but it looks like this:
As you can see, it's how mathematicians show us they are better than we are.
Overall, map projections have showed me the amazing diversity of possible projections and their infinite applications. Equal-area projections are much better suited for statistical analysis, while conformal maps are better for navigation. Equidistant maps have a narrower use, but are very straightforward, as their name states. The beauty of this exercise however, is that it illustrates how easy it is the use ArcGIS to go from one projection to another. I even messed around with other projections not under the "world" subcategory. The ones centered on the poles are very interesting and give a completely different look at the Earth. This makes GIS very accessible and enables user generated GIS. Unlike the previous lab, creating different projections was very easy and intuitive. So long as you understand the application of each projection, you can create a plethora of models for use in something like conservation biology, which as my major, is what makes me drool the most.
Two thumbs up!
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