CARTOGRAPHIC PROJECTIONS
First of all, in this post of the blog we are going to
show you the activities which were proposed before doing our task:
A map is the only “perfect”
representation of the Earth’s surface. All maps are distorted in four major
ways. The four ways maps are distorted is by the shapes, sizes, lines and latitude of the landmasses being
mapped. In order to make maps, projections must be made, and different
projections require different distortions.
Projection
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Robinson
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Mercator
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Azimuthal
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Purpose
|
Attempt to find a
good compromise to the problem of readily showing the whole globe as a flat
image. This projection was developed to show the entire Earth with less
distortion of area.
|
Representing the
spherical Earth surface on a cylindrical surface that generates a terrestrial
plane map when it opens.
|
Illustrate the
“World view” (with respect to this distance and initial direction) of a bird
situated at the projection centre an adapted it for migration along
orthodromes.
|
Distortion-Types?
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The straight
parallels imply severe angular distortion at the high latitudes toward the
other edges of the map, a fault inherent in any pseudocylindrical projection.
|
Mercator projection distorts the size and shape of large objetcs, as the scale increases from the Equator to the poles where it becomes infinite.
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This projection has no
distortion because it is equidistant.
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Distortion-Areas that are most distorted?
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Distortion close the
poles are severe, but quickly decline to moderate levels moving away from
them.
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Distances near the
poles are greatly distorted making them look much larger.
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The distortion of
the areas and angles increases when it grows the farther away from the centre
of the map.
|
Problems?
|
This feature requires a trade-off in terms of inaccurate map direction and distance.
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One
disadvantage of a Mercator projection is the distortion at high latitudes.
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The distances from all
other points are incorrect, and areas and shapes get distorted. More than one
moves away from the centre of the projection.
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Socio-cultural implications of using it as a
learning resource
|
As the distance
between continents is wrong, children grow up thinking misconceptions.
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It occurs the same
thing that in the Robinson projection. In this model, Germany is in the
centre of the map.
|
This projection is
the most real and recent. The children learn the true size and distance of
the countries. But they do not use this model, because the most used are the
two previous projections.
|
Once this is done, it is important to mention the
definition of map projection. This is a systematic
transformation of the latitudes and longitudes of locations on the surface of a sphere or an ellipsoid into locations on a
plane. Map projections are necessary for creating maps and all map projections
distort the surface in some fashion. Some distortions are acceptable and others
are not; therefore different map projections exist in order to preserve some
properties of the sphere-like body at the expense of other properties. There is
no limit to the number of possible map projections. "Map projection"
also refers specifically to a cartographic projection.
This task consists in three projections
explained above, Robinson, Mercator and Azimuthal projection. We have chosen
the Azimuthal projection. With
this projection, the spherical grid is projected onto a flat plane, thus it is
also called a plane projection. The poles are the "normal aspect" which
results in the simplest projected grid for this family of projections. That is,
the plane is normally placed above the North or South Pole. Normally only one
hemisphere, or a portion of it, is represented on Azimuthal projection. When
projected from the centre of the globe with the normal aspect, the typical grid
appearance for Azimuthal projection shows parallels forming concentric circles,
while meridians radiate out from the centre. If the imaginary projecting light
source is inside the globe a gnomonic projection results, if the light is
antipodal a stereographic, and if at infinity, an orthographic. The flag of the
United Nations contains an example of a polar Azimuthal equidistant projection.
We have chosen the Azimuthal projection because,
although it is the oldest projection among these three projections, as some of
you know this is the most real projection, it has less distortion than the two
other projections which we have studied. Although teach this presentation to the
children it is more difficult than the others, we think that it is more
correctly to explain it because as we have said before, it is the most real.
The following step is to compare France and Mexico,
the two countries we have chosen with the three projections.
1.
Robinson.
According to Robinson's projection Mexico is two and a
half bigger than France in size.
The number of habitants in
France is 63.952.494 while the number of habitants in Mexico is 118.115.955 so
that the number of habitants in Mexico is bigger than in France as well as the
size of the country. Robinson's
projection is less real than the other projections but, this projection
is the most used. He presents a conic projection of his map.
2.
Mercator.
Mercator projection shows that Mexico is twice bigger
than France in size. We can locate France and Mexico in
Mercator's projections looking at the latitude. France is located in 0◦ meridian
and 40◦-45◦ parallel. Mercator's map is the only one where we can find the
localization based on the latitude. Also, America is more at the South of the world;
France is bigger represented than its real size in order to give to the country
major importance.
This projection is better to use in textbooks because
it is plane and rectangular. Mercator's
projection overestimates the white man putting Germany as the centre of
the world. Also, the continents are closer and the oceans are smaller so that colonialists
believed that the distance between continents was smaller than they thought.
The map presents a cylindrical shape.
3.
Azimuthal.
Azimuthal projection presents that Mexico is three
times bigger than France in size.
This perspective compared with Mercator's and
Robinson's projection is the most real and recent. Each country have the
correct position on the map, each country have the same importance. Children
learn the correct size of each country but this perspective is not used at all
at schools.
MEDIA
The following step in this task was to explain how the
effects of media distort the reality. We have chosen this picture to illustrate
that with the same object, in this case, an egg, depending on the person
itself, their way of thinking, their background, the way that they were
educated, etc. So that, they have different perspectives of the same object.
This is an example of a distortion in our daily life.
In this case, we can see in the picture an egg which
is represented in different ways by Picasso and Dalí. They painted the egg
depending on their appreciation of reality.
TREASURE HUNT
Finally, the last step to do this task was making a
treasure hunt to find answers to some questions given in the content of the
links previously selected by the teacher.
Our treasure hunt was:
A treasure
hunt is a list of activities which allows children learn and have fun at the
same time, it includes different games, tasks, or anything that the teacher
considers useful for their students’ learning.
In order to
teach the animals to our students, we would do an activity where we give them some
pictures of animals and on the blackboard they have got the different
categories of vertebrated animals: fish, amphibians, mammals, birds and
reptiles. They have to put each picture on its respective category.
For
example: One child has a picture of a dog, so he has to put it in the mammals
category.
In this
way, they can learn the classifications with a fun and easy activity at the
same time they will have a good time while they are learning new things.
With this task we have learnt a lot of things we did
not know. Now, we realize that we learn in the school things that are not real,
such as in this case, the maps. In most cases of the girls in the group, we
learnt Geography or History with the maps of Robinson or Mercator, but not with
the more real, the Azimuthal projection.
To sum up, we have to add that we enjoy so much this
task and we hope you learn a lot of things with us. In the final presentation, we can conclude that it was very difficult to agree because the groups were very big and there were different opinions.
Regards!
