For this lab exercise, I
created six different map projections of the world, and each gave
dramatically different distances for the line between Kabul, Afghanistan
and Washington, D.C. The standard true distance is 6,934.48 miles, but
the fact that each projection had different distances from this shows
that map projections cannot be trusted too easily and whoever uses them
must be wary of the kind of distortion involved. It seems peculiar to me
how each projection can really only be used for a specific, narrow
purpose, since each projection differs in where and how it decides
to allow distortion. This means that whoever references a map must be
extremely careful in identifying the map's projection and must be aware
of where and how the distortion is distributed to avoid making drastic
errors in measurements.
For the equidistant map
projections, I chose the Azimuthal since it is used in the United
Nations logo, as well as the equidistant cylindrical. It is true that
the equidistant projections are perhaps better for maintaining scale
throughout the map, but evidently by looking at the Azimuthal projection
and the equidistant cylindrical projection, even they are not the same
in terms of distance. For example, the distance between Kabul and
Washington, D.C. is three thousand more miles in the Azimuthal
projection. Thus it is a disadvantage inherent in the map that distance
is only true in relation to the center point, but not to all other
points. Also, there is more and more distortion of shape and area going
along the latitude lines as you move along the map away from the center
of the projection. For example, in the Azimuthal projection, Australia
and nearby Pacific Islands are stretched far beyond their original shape
because they are far from the center point of the map.
The
equal area map projections are best for showing the actual size of the
land masses. I personally prefer equal area map projections most because
they show how large each land mass is in relation to the other land
masses, and thus show how things really are in relation to each other. I prefer the Mollewide projection in particular because it also
preserves distance and shape relatively well, and it visually resembles
the compromise and trusted Robinson projection. I admire how the Bonne map has the
distance between Kabul and Washington, D.C. that is closest to the
standard distance, but it has a downside in that it severely distorts the shape of the land masses
to the point where even some of them are hard to see, such as
Australia.
It was
interesting but not surprising that the conformal map projections had
the distances between Kabul and Washington, D.C. that was most different
from the standard distance. Conformal projections probably have the
most distortion out of all the map projection types because they do not
attempt to preserve any kind of true measurement. It is understandable
why elementary schools like to use conformal projections, like the
Mercator, to teach children about the world and what it looks like, but
evidently we can see that such projections dramatically distort
size. It seems though as if the Mercator projection is preferable over
the stereographic projection, however, if you care more about equal area, since
the stereographic projection severely distorts the size of all land that
is far away from the center point of the map: namely, everything besides Africa and the
Middle East. The Mercator is more preferable because it distorts while moving away from a line (the equator) rather than a single point,
therefore having severe distortion over a smaller area.
It
is lucky, however, that most maps are of a larger scale than world maps and cover
less area, thus minimizing the amount of distortion involved. It is mostly only
when dealing with world maps do we encounter distortion to worry about.
