September 19, 2012
Introduction
- "The end result and final goal of all geographic investigations, explorations, and
surveys is the depiction of the Earth's surface: the map. The map is the basis for
geography. The map shows us what we know about our Earth in the best, clearest, and
most exact way."
- August Petermann
Geographer
- Map: a geographic representation of a part of the Earth's surface
- Essential quality of maps - they are representations of a locality or place, i.e.,
maps are locational images
- Questions:
(1) What do maps tell us?
(2) How should we read maps?
(3) Why are maps so important to geographers?
The Elements of Maps
1. The Global Grid
- Key reference points which enables us to determine "where" something
is located on the Earth
- North Pole
- South Pole
- Equator
(Each of these is given in nature)
- Prime Meridian
(Agreed upon by cartographers as the meridian of longitude which asses
through the Royal Observatory at Greenwich, England)
- Given these four reference points and the fact that a circle (Earth) contains 360
degrees, then:
- The distance between the poles is 180 degrees, and the distance between the
equator and each pole is 90 degrees.
- Latitude
(1) Measure of distance north and south of the equator
(2) Parallels of latitude run east-west
(3) All parallels of latitude are parallel to each other and to the equator
(4) Parallels decrease in length close to the poles
- Longitude
(1) Measure of the angular distance east/west of the Prime Meridian
(2) Meridians of longitude run north-south
(3) All meridians are of equal length, and each meridian is one-half the
length of the Equator
(4) All meridians converge at the poles
- Combining lines (parallels) of latitude with lines (meridians) of longitude, we
get a grid in which:
(1) Meridians and parallels intersect at right angels
(2) The scale (see below) on the surface of the earth is the same in every
direction* * Only the globe itself retains these characteristics. When the grid is projected onto a flat
surface, distortion occurs.
2. Scale: The relationship or ration between the size of a feature on a map and the same
feature on the Earth's surface.
- Example: A 1:50,000 scale means that 1 inch on the map represents
50,000 inches on the Earth's surface
- Note:
- (1) The smaller the scale, the larger the area being represented on
the map? (Why is this the case?)
- (2) A smaller scale map is more generalized (less detailed) than a
large scale map (which is more detailed)
Types of map scales:
(1) Graphic line scales
(2) Verbal scale - "1 cm on the map represents 1km on the Earth"
(3) Representative fraction 1:50,000
3. Projection
- Critical challenge facing cartographers: How to display the curved
surface of the earth on a flat sheet of paper?
- Map Projectio
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