Map projections are very important because they give us sphere data on to a flat surface. There is always a distortion that comes with any map projection. The map projections used for this exercise represent certain characteristics more than others. The equidistant preserves distance, conformal preserves shape and direction, and equal-area preserves area.
In the equal-area projections I chose the Mollwiede and Bonne projections. Mollwiede the shape is fairly accurate although since it’s a representation of a sphere it makes areas smaller when it gets closer to the poles and bigger toward the equator. The actual mileage from Washington D.C. to Baghdad is 6,211miles but according to the Mollwiede it is 6,587miles and according to Bonne it is 6,035miles. Bonne looks especially distorted but it does keep the general shapes of the continents except for Australia, which is very stretched.
Equadistant projections are meant to preserve distance, which is proven by the maps. In Sinusoidal the areas closest to the poles are the most stretched/distorted. Otherwise, the map is fairly accurate. The Washington D.C. to Baghdad distance on this projection is 6,774miles. The distance for the second equidistant projection, Equadistant Conic, is 6,341miles, which is closest to the actual mileage out of all the projections. This map is very distorted because the continents near the North Pole are very small and as you go to the South Pole the continents get bigger making Antarctica look the same size as the rest of the continents combined.
The conformal projection, Gall Stereographic, is a common sight when it comes to maps but it does blow the north and south poles out of proportion and keeps the rest of the continents shaped correctly. In the conformal projections the longitudinal lines are made even which keeps the direction right. The Mercator is extremely distorted at the poles. This projection puts the distance between Washington D.C. and Baghdad at 8,395miles which is very far from the correct mileage and the Gall Stereographic projection is only a bit closer at 5,942miles.
Coordinate Systems & Projections Worksheet
1. What is an ellipsoid? How does an ellipsoid differ from a sphere?
An ellipsoid is an even oval shape that represents the shape of the earth. A sphere is different from an ellipsoid because it is perfectly round where an ellipsoid has a more squished shape.
2. What is the imaginary network of intersecting latitude and longitude lines on the earth's surface called?
Geographic Coordinate System
3. How does the magnetic north differ from the geographic North Pole?
The magnetic North is where a compass points because of the magnetic pull where the Geographic North Pole is one of the points the earth's axis rotates from.
4. Why are datums important? Briefly describe how datums are developed.
Datums are important because they give us a better representation of the earth's surface that is more detailed than latitude and longitude. Datums come from points surveyed in a specific region or country.
5. What is a map projection?
The process of putting the round earth on a flat surface: 3-D to 2-D and there are many different ways to do this effectively.
6. What is a developable surface?
A shape which the earth is transformed from an object to a flat surface, for example a cone or cylinder.
7. Which lines on the graticule run north-south, converge at the poles, and mark angular distance east and west of the prime meridian?
a. Lines of longitude
b. The major axes
c. Parallels
d. Lines of Latitude
8. Which of the following ellipsoids is now regarded as the best model of the earth for the region of North America?
a. Clarke 1866
b. International 1924
c. GRS80
d. Bessel 1841
9. Which well known coordinate system would be appropriate to use for developing and analyzing spatial data when mapping counties or larger areas? Why?
Universal Transverse Mercator System, because it separates large areas into areas of 60 degrees longitude.
10. What is a great circle distance?
The shortest distance between two points on a sphere but by drawing a line on the outside of the sphere and not going through it.
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