MAPS PROJECTION: HOW MAPS ARE MADE

I. MAPS: HOW ARE THEY MADE?

A sort of introduction:

http://www.olc.spsd.sk.ca/DE/k9mod/Mapskill/mod3fl5.swf

Suppose we want to find a buried treasure, and the only person who knows where the treasure is cannot travel with us. How will we find the treasure? The individual who knows where the treasure is could describe to us in great detail how to get to and find the treasure. This might work, but what happens if we forget an important part of the instructions? We would have to travel all the way back and have them repeat again the description of where the treasure is hidden. We could have them write the description down for us. That way, we will not forget it. Having these instructions in hand, we can easily refer back to them as needed. A list of written directions would be a more useful tool, but what would happen if we got lost? Once we were off course, the written directions would no longer be of any use to us. These instructions only specified how to find the treasure from one specific starting point, and not from our current lost position. A map solves both of these problems.

Image

Drawing a detailed map of the area around the treasure would allow us to take something with us so that we don’t forget. If we get lost, we simply determine where on the map we are, and then continue towards our destination.

A map is a two dimensional description of a specific area of land. Maps describe in a visual or graphic format certain key features of the territory being examined. For example, a road map of the province of Santander shows many of the important state roads and how they interconnect. A roadmap might also show the towns and cities, as well as a few of the more popular destinations within a state. Other maps might show the distribution of birds along the wetlands of the Great Salt Lake, or the distribution of human populations throughout the world.

Maps are important tools and are indispensable to geographers. They help geographers understand in a visual way important things about the surface of the Earth. In the modern world, our ability to view and map the Earth is much improved. However, even today it is impossible to draw a flat map that is 100% accurate. This is due to the impossibility of recreating the surface of a round planet on a flat map. The smaller an area that a map represents, the more accurate that map will be.

II. GLOBES AND MAPS

Globes help us understand our planet. They have a very important role in helping us understand the shape of our home planet, wich is a sort of flat-shaped by the poles figure, called “geoid“. Despite their usefulness, globes have many disadvantages as well. The biggest of these disadvantages is due to the fact that globes represent the entire Earth. Because of this, they will always be small scale representations of the Earth. This means that it is difficult to show very much detail on a globe. Another disadvantage of a globe is that their awkward size and shape makes them difficult to carry around. Globes are the most accurate way to represent the surface of the Earth; however, it is not practical to carry a globe into the field, so map makers must figure out how to represent a round map on a flat piece of paper, or on a flat screen.

III. PROJECTING OUR GLOBE ONTO A FLAT SURFACE

Globes are the most accurate way to represent the surface of the Earth. However, because it is not practical to carry a globe into the field, map makers must figure out how to represent a round map on a flat piece of paper, or on a flat screen. Consider the challenge of gift wrapping a rubber bouncy ball. What happens as you place gift wrap around the ball? Can you wrap the ball in such a way so that the paper is perfectly flat? No matter how long you try, you cannot cover a round object with flat piece of paper without creating wrinkles, folds, or cuts in the paper.

Over the centuries, many different ways of representing the round Earth on flat paper have been developed. Each of these methods is referred to as a map projection. What does it mean to project something? Have you ever been to the movie theatre? How does the movie get on the movie screen? The image you watch on the screen is projected using a high powered light from the back of the theater. Now, imagine placing a projector inside of a globe and projecting the different continents, islands, and other features onto a flat screen. What would the projection look like? This depends on where you place the screen.

1. Cylindrical projection

A cylindrical projection map is the most common type of map that we see. Imagine placing the movie screen around the globe in a cylinder shape. The projection that results is depicted in this image. Notice that areas close to the equator have very little distortion. However, the closer to the poles that one travels, the more distorted the map becomes. In this example, Greenland appears to be many times larger than it really is.

cylincrical projection

2. Conic projection

A conic projection map is created by placing a cone shaped screen on a globe. The resulting projection is more accurate than the cylindrical projection map discussed above. However, the further we travel down the map, the more distorted and less accurate the map becomes.

conic projection

3. Plane projection

A plane projection is created by placing an imaginary screen directly above or below a globe. The image that would result is called a plane projection. This type of map projection is not commonly used.

planar projection

Video on map projections: http://www.youtube.co/watch?v=X4wgFSHZXBg

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