Map Projections Lecture
World Geography
Mr. Wiggins
To see the whole world as it really is, we must look at a globe. It is the only map
that shows the true sizes and shapes of all land and water areas, true distance
and—what is most important today—true geographical relationships. Therefore,
the most accurate map of the world is the globe!
Concerns of Map Makers:
1.
2.
3.
4.
Distance
Shape
Size/Area
Direction
Map Projections:
*Imagine trying to flatten the whole peel of an orange on a table;
*you would have to cut or stretch parts of it to flatten it.
*Mapmakers face a similar problem in showing the surface of the round Earth
on a flat map.
*When the Earth’s surface (which is a sphere) is flattened, big gaps open up.
*As a result, mapmakers have developed different projections (ways of showing
the Earth on a flat piece of paper).
*Each map projection has its strengths and weaknesses, or pros and cons.
Mercator/Cylindrical Projection:
*This is called a Cylindrical Projection b/c it is designed from a cylinder wrapped
around the globe.
--imagine a light bulb suspended in the middle of the globe shining
out and projecting the shadows of the Earth’s features onto the cylinder of
paper, and the mapmaker tracing those features
*The point on which the cylinder/paper is touching the globe is called the
TANGENT POINT (this is the most accurate part—the map becomes more
distorted the further you get from the tangent point)
Pros
//
Cons
*shows land shapes accurately / *fails to show true size & distance
*shows true directions
/ --the farther away from the equator (tangent
/
point) the greater the distortion
/ --accurate only in LOW LATITUDES
/
*Ex: Greenland looks huge in comparison
to other land masses—it’s not really that
big!
Conic Projection:
*Notice that the root of “Conic” is “cone”
*This is designed from a cone being placed over a globe
Pros
//
Cons
*shows land shapes accurately / *fails to show true size & distance
*shows true directions
/ --most accurate along the lines of latitude
/
where the tangent point is—MID LATS!
/ --only useful for areas in mid latitudes with
/
long east-west dimensions (United States)
/
*distortion increases as you get further from
/
the tangent point
Flat Plane Projection:
*Designed from a flat plane touching the globe at one point (North or South Pole)
Pros
*shows land shapes accurately
*shows true distances close to
the center/tangent point
//
Cons
/ *distortion increases as you get further from
/ the center/tangent point—HIGH LATS!
/
Robinson Projection:
*This is the most-common map used in American classrooms
Pros
*shows land shapes accurately
and does a good job in
balancing distortion
//
Cons
/ *polar regions are flattened & stretched
/
/
Goode’s Interrupted Projection:
*This is the most accurate flat map!
The Great Circle Route:
*When travelling long distances on the Earth, it is advisable to follow Great
Circle routes b/c they always represent the shortest distance betw. two points.
*Drawing a straight line on a flat map WILL NOT show the shortest route betw.
two places.
*Remember, maps represent a ROUND world on a FLAT plane
*The shortest route betw. any two points on the planet is a GREAT CIRCLE
ROUTE--airplanes & ships navigate along these routes
*Any line that divides our Earth into equal parts is a Great Circle
--the equator is a Great Circle
Ex: Looking at a flat map, how many degrees would you travel betw. Anchorage, AK
(60ºN, 150º W) and St. Petersburg, Russia (60º N, 30ºE)? Now, looking at a globe, take
the Great Circle Route. How many degrees did you travel by taking the Great Circle?
The Analemma:
*This resembles a figure-eight on the globe and identifies the location of the sun’s
direct rays and shows the accuracy of our clocks
*Winter Solstice (December 21)
*Spring/Vernal Equinox (March 21)
*Summer Solstice (June 21)
*Fall/Autumnal Equinox (September 22)
FOR NORTHERN
HEMISPHERE