The concept of map projections has a pivotal significance,
since it allows for information on a three dimensional object to be displayed
on a two-dimensional plane. Even though in order to make a map of smaller areas,
a map projection is not necessary, it is important that some sort of map
projection be employed when displaying larger areas, such as the entire surface
of the Earth. Map projections are crucial, since they are required to make useful
maps that to some extent accurately display relatively larger areas. It is
significant that a developable surface, such as a cone, cylinder, or plane can be
utilized in order to project a map. For example, if a cone is used, it can be
imagined to be “wrapped” around a model of the Earth, such that there forms one
tangent line or two secant lines. The surface of the Earth can then be
projected onto the cone, which can at that point be “unwrapped.” Such a conical map projection is used in the equidistant
conic projection created in the lab. A similar
process can be used to project on to the cylinder as well. An example of a
cylindrical map projection can be seen through the equidistant cylindrical
projection created in the lab. If a plane is used for a map projection, it can
be imagined that a model Earth lies in front of the plane and that a flashlight
is behind the model Earth. The shadow that is created onto the plane is the
portion of the surface of the Earth that will be projected upon the plane to form the map. Even
though a three dimensional globe is the most accurate representation that can
be achieved, it is in some cases impractical to use a globe. For example, a map
can be more easily transferred and accessed than a globe. It is also easier to
create an extremely large map by adjusting the scale, whereas the creation of
such a globe and its use would be more difficult.
There are
some prevalent problems, however, in creating a map through the use of map
projections. Since, the Earth is a three-dimensional object, displaying the
surface of the Earth onto a two dimensional object results in a distortion of
some aspect of the image displayed on the map.
Attributes such as direction, distance, area, and shape are affected by the
potential distortions that occur with map projections. Different map
projections distort different attributes of the map. In many cases certain
aspects of the map must be sacrificed in order to better display some other aspect.
Therefore, some map projections may be better at maintaining, say, shape, while
other map projections may be better at giving more accurate measurements of
distance. Consequently, the main drawback of map projections lies in their
inability to preserve direction, distance, area, and shape simultaneously.
Looking
into the three different types of map projections illustrated in this lab as examples, the different
traits of each projection can be more easily analyzed. Each projection has its
own distinct and unique advantages. The conformal projections do not distort
angle measurements and also preserve shapes for small areas. Maps that utilize
conformal projections may be used for navigational purposes. The Mercator
projection has profound advantages for navigational purposes, because it can
display straight rhumb lines, which are lines of true direction. The equal area
map projections, on the other hand, preserve area at every location on the map
in comparison to the Earth’s surface when accounting for the scale difference.
The equidistant map projections preserve distance with a certain limitation.
Distance is preserved from the point where the map projection is centered. For
example, if Los Angeles, California
was used as the location to center the map, the actual distance could be
measured from Los Angeles to Washington
D.C. and from Los Angeles
to New York.
If one were to measure distance from New York
to Washington D.C., however, the projection would not
preserve distance in this case.
The use of
map projections has certain real life implications that in some cases have
become controversial. For example, if a conformal map projection, such as the
Mercator projection is used to display the world, the area of the continents is
distorted. The continents closer to the equator appear smaller, whereas the
continents farther away appear larger. For example, the size of Antarctica and Greenland is significantly distorted on a Mercator
projection. This is because the scale is not constant and continually increases
farther and farther away from the equator. The use of this common map
projection has become controversial, because European countries and the United States are illustrated to be bigger,
whereas the South American countries and Africa,
especially, are projected to be considerably smaller than their actual relative
size. Therefore, some people familiar with the matter have come to propose that
this causes discrimination against the inhabitants of those continents and countries.
They associate a psychological affect with the matter, stating that the
inhabitants of these countries come to perceive themselves as less powerful and
inferior to the inhabitants of the apparently larger European countries and the United States.
This is because these inhabitants view their countries to be smaller and weaker
in comparison to the countries of the northern world. Therefore these people advocate
that a new common map projection be used that restores the relative sizes of
the continents, so that this sense of inferiority is eliminated.
No comments:
Post a Comment