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Welcome to our first slide cast lecture in World Studies! This lecture will cover different
projections of the world map. After this lecture, you will be asked a series of questions on
the advantages and disadvantages of each projection.
Slide 1: Mercator Projection
This is the same projection that you see most on classroom maps, including the map in this
classroom. The Mercator map is made by wrapping a piece of paper around a globe in the shape
of a cylinder. The cartographer, or map maker, then turns on a light in the center of a transparent
globe and traces the lines of the continents onto the piece of paper.
Distances on this map are accurate only along the Equator, but are reasonably correct within
15° of Equator. This map makes land masses north of the tropic of cancer and south of
the tropic of capricorn appear much larger than they really are. The effect is that nations
like the US and Canada appear much larger than they really are in relation to nations
like Morocco or Nigeria.
Slide 2: Miller cylindrical
The Miller cylindrical map is similar to the Mercator projection in that it is used to
represent the entire Earth in a rectangular frame and with a cylindrical projection. It
avoids some of the scale exaggerations of the Mercator by attempting to scale down the
land mass with the northern and southern regions of the globe. However this map still distorts
the land mass the further north or south you move from the equator.
This map was first presented by O. M. Miller in 1942.
Slide 3: Robinson Cylindrical
This map is also a cylindrical map like the Mercator projection. It is also like the Miller
projection in that it uses mathematical proportions to scale down the distortion at the high latitudes
in the northern and southern hemispheres. This projection does provide a better balance
of size and shape of high-latitude lands than does the Mercator projection. Nations like
the Soviet Union, Canada, and Greenland appear truer to size.
This map is most accurate along the equator, and most distorted still around the poles.
This map is used in Goode's Atlas, adopted for National Geographic's world maps in 1988,
appears in growing number of other publications, may replace Mercator in many classrooms.
It was first presented by Arthur H. Robinson in 1963.
It is a pseudocylindrical projection.
Slide 4: Sinusoidial Equal Area No, it's not sinusitis, it's sinusiodial!
To create this map, cartographers peeled back the surface of the globe and laid it flat
on rectangular surface then traced the shape of the continents. The advantage of this map
is that there is no distortion near the poles; in other words, every line of latitude is
proportional and northern territories don't appear bigger than they are in reality. However,
the disadvantage is that there are interruptions in the map.
This type of may was first used in 1570. It is also a pseudocylindrical map because it
is mathematically based on a cylinder tangent to the Equator.
Slide 5: Orthographic
The orthographic map has been used for perspective views of the Earth, Moon, and other planets.
Cartographers created this map by placing a flat sheet on top of a transparent globe
and then tracing the shapes of the continent onto the flat surface. The most common type
of orthographic map is a picture of the Earth as it appears outer space. The distortion
on this map occurs around the edges, and it is most true at the point where the flat paper
touches the globe. In other words, the directions are true only from center point of projection
and the scale decreases along all lines radiating from center point of projection. Any straight
line through center point is a great circle. Distortion increases away from center point.
The Orthographic projection was known to Egyptians and Greeks 2,000 years ago.
Slide 6: Azimuthal
As you can see, the Azimuthal map is similar to the Orthographic map in the previous slide.
It is made in the same way by placing a plane on top of the globe, but like the Robinson
Projection, it uses a math scale to temper the distortion on the periphery of the map.
This map has been used most frequently for for seismic and radio work. It is also the
map that is used by pilots to calculate distances between destinations. It is also the map that
appears on the UN Emblem. Distances and directions to all places true only from center point
of projection. Distances correct between points along straight lines through center. All other
distances incorrect. Distortion of areas and shapes increases away from center point.
Slide 7: Albers Equal Area Conic
This map is made by placing a cone around a portion of the globe. Like the cylindrical
and Orthographic projections, the map is most accurate along the line where the cone touches
the globe. This map is useful for large countries or other areas that are mainly east-west in
extent and that require equal-area representation: the US and Russia are such nations. Distortion
on this map increases the further away the cartographer is from the point of contact.
Because this map tends to be used for regional maps that are more limited in scope, it tends
not to distort as much.