# Dufferin Peel by mikeholy

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```									http://www.colorado.edu/geography/gcraft/
notes/mapproj/mapproj_f.html
Introduction
• Map projections are attempts to portray the surface of
the earth or a portion of the earth on a flat surface. Some
distortions of conformality, distance, direction, scale, and
area always result from this process. Some projections
minimize distortions in some of these properties at the
expense of maximizing errors in others. Some projection
are attempts to only moderately distort all of these
properties.
Globes versus maps
1. Shapes of things are true
2. Areas are true
3. Scale is constant
4. Directions are true
In a map, one or more of these is
lost
It is difficult to accurately “flatten”
a sphere
Example of map “problem”
A
A is true shape and size on a globe

A and B are same shape but
B              different in area

C                  A and C have same area but
are different in shape
Map projections: methods for
“flattening” the sphere
Projections
•   Shape (Conformality)
– When the scale of a map at any point on the map is the same in any direction,
the projection is conformal. Meridians (lines of longitude) and parallels (lines of
latitude) intersect at right angles. Shape is preserved locally on conformal maps.
•   Distance
– A map is equidistant when it portrays distances from the center of the projection
to any other place on the map.
•   Direction
– A map preserves direction when azimuths (angles from a point on a line to
another point) are portrayed correctly in all directions.
•   Scale
– Scale is the relationship between a distance portrayed on a map and the same
distance on the Earth.
•   Area
– When a map portrays areas over the entire map so that all mapped areas have
the same proportional relationship to the areas on the Earth that they represent,
the map is an equal-area map.
Map projections fall into four
general classes
•   Cylindrical
•   Conic
•   Azimuthal
•   Miscellaneous
Cylindrical Projection
• Cylindrical projections
result from projecting a
spherical surface onto a
cylinder.
• When the cylinder is
tangent to the sphere
contact is along a great
circle (the circle formed
on the surface of the
Earth by a plane passing
through the center of the
Earth)..
Cylindrical projections

Least distortion along line of tangency,
where projection surface touches globe
Conic Projection
• Conic projections
result from projecting
a spherical surface
onto a cone.
• When the cone is
tangent to the sphere
contact is along a
small circle.
Conic projections

Least distortion along line of tangency,
where projection surface touches globe
along standard parallel.
Azimuthal Projection
• Azimuthal projections
result from projecting
a spherical surface
onto a plane.
• When the plane is
tangent to the sphere
contact is at a single
point on the surface
of the Earth.
Planar projection

Least distortion at
point of tangency,         In a polar
where projection           projection, the
surface touches            point of tangency
globe                      is the pole.
Miscellaneous Projections
• Miscellaneous projections include
unprojected ones such as rectangular
latitude and longitude grids and other
examples of that do not fall into the
cylindrical, conic, or azimuthal categories
Cylindrical Projections
Mercator
• The Mercator
projection has straight
meridians and parallels
that intersect at right
angles. Scale is true at
the equator or at two
standard parallels
equidistant from the
equator. The projection
is often used for marine
straight lines on the
map are lines of
constant azimuth.
Peters Projection
The Peters
projection is a
cylindrical equal-
area projection
that de-
emphasizes
area
exaggerations in
high latitudes by
shifting the
standard
parallels to 45 or
47 degrees.
Comparing Mercators to Peters
Projection
The Peters Map vs The Mercator
Map
The Greenland Problem
Greenland: 0.8 million sq. miles

Africa: 11.6 million sq. miles
The North compared to the South
The North is 18.9 million square miles.
The South is 38.6 million square miles.
Europe compared to South
America
Europe is 3.8 million square miles.
South America is 6.9 million square miles.
Africa compared to the Former
Soviet Union

The former Soviet Union is 8.7 million square miles.
Africa is 11.6 million square miles.
Greenland Compared to China
Greenland is 0.8 million square miles.
China is 3.7 million square miles.
Important characteristics of the Peters Map
•    The Peters Map is an equal area map.
•    This new map shows all areas -
whether countries, continents or
oceans - according to their actual size.
Accurate comparisons become
possible.
•    The Peters Map is an equal axis map.
•    All North-South lines run vertical on
this map. Thus, geographic points can
be seen in their precise directional
relationship.
•    The Peters Map shows equal
positions.
•    All East-West Lines run parallel. Thus
the relationship of any point on the
map to its distance from the equator or
the angle of the sun can readily be
determined. Fairness to All Peoples
•    In the complex and interdependent
world in which nations now live, the
people of the world deserve and need
an accurate portrayal of the world.
•    The Peters Map is the map for our
day.
Conclusion
• Why is Europe at the top half of maps and Africa at the
bottom? Although we are accustomed to that convention,
it is, in fact, a politically motivated, almost entirely
subjective way of depicting a ball spinning in space.
Maps do not portray reality, only interpretations of it. To
begin with, they are two-dimensional projections of a
three-dimensional, spherical Earth. Add to that the fact
that every map is made for a purpose and its design
tends to reflect that purpose. Finally, a map is often a
psychological projection of the historical, political, and
cultural values of the cartographer--or of the nation,
person or organization for which the map was created.

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