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