Geography Reference
In-Depth Information
Exercises
1.
Projections for Different Needs
If you collect maps from magazines and newspapers for a few weeks, you will have
a pretty sizeable collection of different kinds of maps and different kinds of projec-
tions.
Come up with a list of different uses of maps and the projections used for each
use.
Think about how projections can preserve the shape of things on the earth, their
size, or the distance from a point or along a line or must compromise between these
three projection properties.
Knowing what you do now about the different qualities of projections, what do
you think about newspaper maps that do not indicate the projection? Are they com-
mon? What kind of errors do you think can arise?
If possible, you also can explore the collection of maps and atlases in a nearby
library.
2.
Questions for Map Projections
1. Is the map whole or broken up?
2. What shape does the projection make the map?
3. How are features (continents and islands) arranged?
4. Are gridlines curved or straight?
5. Do parallels and meridians cross at right angles?
3.
EXTENDED EXERCISE: Sinusoidal Projection
Overview
In this exercise you will calculate values for a sinusoidal projection that you produce.
Concepts
The location of a point ( x , y ) in a sinusoidal equal area projection is calculated for
this exercise in two steps. First, the longitude value is transformed to east-west val-
ues ( x ) by multiplying the longitude value times the radius and times the cosine of
the latitude. Multiplying the longitude values by a cosine of latitude creates the grad-
ually increasing distortion of areas further away from the equator. The north-south
values ( y ) of the projection are calculated through a linear relationship between the
radius and the latitude. Second, you will scale the calculated x and y values to fit a
map on a piece of paper by determining a scale ratio that transforms the radius of
the sphere (6,371 km).
 
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