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INTRODUCTION TO PHYSICAL GEOGRAPHY:
Chapter 1 The “spheres” of Earth
• Hydrosphere• Lithosphere• Atmosphere• Biosphere
The earth is elliptical. Which shape type is correct, and why?
• note: ellipticity exaggerated in photos!
Earth’s dimensions
Figure 1.8
Geodesy: Earth Division
• Latitude:
1 degree = 69 miles
60 minutes = 1 degree
(1 minute = 1.15 miles)
1 nautical mile = 1.15 miles
1 second = 1/60 of 1 nautical mile
• Longitude: lines are not parallel, are called "meridians”-At equator only:
1 degree = 69 miles But declines to zero at
the poles
Latitude
Figure 1.10
Longitude
Figure 1.12
Lines of latitude to know:
• Equator (O°) starting point to number parallels• Tropic of Cancer (23.5° N)• Tropic of Capricorn (23.5° S)• Arctic Circle (66.5° N)• Antarctic Circle (66.5° S)
Important Meridians to know
• Greenwich or “Prime” (goes through England). Is starting point (0°) for numbering longitude
• International Date Line: (180° E&W) the place where new days start; is halfway around the world from Greenwich Meridian
Distance on a Globe
Question: The shortest distance between two points is:
a) a straight line
b) A Great Circle Route
c) All of the above
Answer: c)
A Great Circle Route is a circle formed by passing a plane through the exact center of a perfect sphere. Cuts earth into two equal sized pieces.
Great Circles and Small Circles
Figure 1.13
MAPS
• The “perfect map” representation of the earth is a globe
• True maps are two dimensional: problem of representing a round earth surface on a flat one.
• The problem with globes is one of scale (example: how large would a globe have to be to include details of Monmouth, Oregon on it?)
Maps and Projections
• Map – a generalized view of an area, as seen from above and reduced in size
• Projection – process of transforming the spherical Earth to a flat map
Properties of Maps
1. Scale: ratio of the size of an object (or distance) on the map to the actual size (or distance) of the object that it represents. Examples 1:100 1:10,000 Which shows more detail?
2. Area
3. Shape
impossible to preserve area and shape over an entire map
Skip Examples of Map Projections
• Read Chapter 1; see Appendix A.
• Ones to be able to recognize: – Mercator (true shape), areas exaggerated at
higher latitudes, useful for navigation– Polar
Isoline Mapping uses lines of equal value
Examples:
1. Topographic maps: lines of equal elevation
2. Isotherm maps: lines of = temperature
3. Isohyet maps: lines of = precipitation
4. Isobar maps: lines of = pressure
Geographic Information Systems (GIS)
GIS is defined as any system which facilitates the analysis of multiple layers of data (maps of specific themes)
GIS System
Figure 1.23