Introduction to Physical Geography

Name: ______________________________________________

GEO 200 Intro to Physical Geography

Assignment 1: Introduction to Earth and Maps

Graticule

To know specifically where something is located on Earth’s surface, a coordinated grid system (that is agreed to

internationally) is needed. The terms latitude and longitude were in use on maps as early as the first century A.D., with

the concepts themselves dating back to Eratosthenes and others.

Adapting from the Babylonians, Ptolemy divided the circle into 360 degrees (360°), with each degree subdivided into 60

minutes (60’), and each minute further subdivided into 60 seconds (60”). This method of dividing degrees into minutes

and seconds is often referred to as DMS coordinates. Note that GIS, GPS, and other computer-based systems often use

decimal degrees or DD coordinates. In this method, each degree is divided into a more familiar base ten system.

Figure 1 Latitude and parallels

1. What is the highest latitude?

2. What is the highest longitude?

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Figure 2 Longitude and meridians

3. List 3 countries that the Prime Meridian passes through.

4. When you look at the Prime Meridian on the globe, which hemisphere is located to the left of the Prime

Meridian?

5. Now locate the International Date Line on the globe. Which hemisphere is located to the left of the IDL?

6. Using a globe, find 30°S, 60°W. What country is located at these coordinates?

7. Starting from the same coordinates (30°S, 60°W), move your finger 20 degrees toward the north. List the

country closest to this location along with the latitude and longitude.

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Figure 3 Measuring longitudes on Earth

8. Figure 3 is a view of the Earth from directly above the North Pole; the equator is the full circumference around

the edge. A line has been drawn from the North Pole to the equator and labeled 0°, representing the Prime

Meridian. Earth’s Prime Meridian through Greenwich, England, was not generally agreed to by most nations

until 1884.

a. Label the Eastern Hemisphere on the above diagram.

b. Label the Western Hemisphere on the diagram.

9. On the diagram above, draw another line from the North Pole to the other side of Earth, opposite the Prime

Meridian, and label it 180°.

a. What is the name of this line (180°)?

b. Use a protractor to measure, draw, and label the meridians that are 100° east and 60°west of the

Greenwich meridian on the above diagram.

10. Why do you think the International Date Line (on the globe) is not straight, but zigs and zags?

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Time Zones

11. Write the longitude for each location and indicate if it is in the Eastern or Western Hemisphere. Then use the

time zone map (projected in the classroom, or on page 25 of your textbook to determine: If it is noon at the

following locations, what time is it in our time zone?

Location Longitude (E/W) Time in VA

Kiev, Ukraine

London, England

Los Angeles, CA

Lagos, Nigeria

Tokyo, Japan

Map Scale

Map scale is the relationship of the distances separating two points on a map to the distance separating the same two

points on the surface of the Earth, measured in the same units. Both the numerator and the denominator must be in the

same units. Scale may be expressed as a fractional scale (ratio or representative fraction), verbally, or graphically.

The denominator of a fractional scale can be difficult to visualize. A verbal scale can concert these to more

understandable units. For example, the denominator of the fractional scale 1:24,000 can be converted by dividing by 12

to get to inches, and by 63,360 to get to miles. So 24,000 inches equals 2,000 feet or .378 of a mile.

We can also set up an equation based on the equivalency statement, and then cross-multiply. For example:

1 foot = 12 inches (start with the equivalency statement)

--------- -------------

X 24,000 inches (fill in the other values, keeping the same units on the same side of the equation)

12X = 24,000 (cross-multiply)

X = 2,000 feet (divide by 12 to isolate X)

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12. Convert the fractional scales to verbal scales using the following conversion factors:

1 foot = 12 inches

1 mile = 5,280 feet = 63,360 inches

Representative fraction: 1:10,000

Verbal scale: One inch on the map represents 10,000 inches or ___________ feet, or ___________ miles on the

ground.

Representative fraction: 1:24,000

Verbal scale: One inch on the map represents 24,000 inches or ___________ feet, or ___________ miles on the

ground.

Representative fraction: 1:3,168,000

Verbal scale: One inch on the map represents 3,168,000 inches or __________ feet, or ____________ miles on

the ground.

13. Compare the fractional scale 1:10,000 to 1:3,168,000. Which would show MORE AREA?

14. Compare the fractional scale 1:10,000 to 1:3,168,000. Which would show MORE DETAIL?

Map Projections

Cartography, or mapmaking, is the study and practice of making representations of the Earth on a flat surface.

Cartographers design maps based on the properties they want to preserve and the information they want to portray.

A map projection is a systematic means to portray shape, area, distance, and direction of the Earth on a two-

dimensional surface. Map projections are created by projecting landmasses and the graticule onto a flat surface. All map

projections contain distortions since no one projection preserves all four properties simultaneously. A globe is the only

accurate representation of shape, area, distance, and direction of the Earth’s surface.

There are three main properties of projections. Equal area projections maintain equal area relationships; conformal

projections maintain angular relationships in order to preserve shape; and equidistant projections maintain distances

between points.

The class of a map projection can be conic, cylindrical, or planar. Conic-class maps result from wrapping a flat surface of

a cone around a reference globe and are often used to project the midlatitudes. Wrapping a cylindrical surface (a

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rectangle) around a globe creates a cylindrical-class map. Cylindrical-class maps are usually centered on the equator. A

planar-class map results from placing a flat surface next to the surface of a globe, so that the two only touch at a single

point, and is most often used to project the poles.

In order to reduce some of the distortion created by projecting a map, cartographers center their maps on a standard

line or point. The points where the developable surface (flat piece of paper with no tears) touches the globe creates the

standard line or point where distortion is minimal. Distortion increases as you move away from the standard line or

point. Generally, cylindrical projections employ the equator as the standard line and thus are greatly distorted in the

higher latitudes. Conical projections typically have a standard line somewhere in the midlatitudes, so this type of

projection is often used for the United States. Planar projections typically have a single standard point because the

developable surface of the plane contacts the globe in only one place.

15. List two advantages that a globe has compared to a map.

16. List two advantages that a map has compared to a globe.

Figure 6 Mercator, Peters, and Goode’s projections

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17. The Mercator projection (conformal cylindrical equatorial) maintains the correct shape of landmasses, but not

their sizes. As a result, Greenland (0.8 million square miles) appears larger than the entire continent of Africa

(11.6 million square miles). The Peters projection (equal area cylindrical equatorial) maintains the correct size of

countries, but not their shapes. Goode’s projection maintains the size and shape of landmasses, but interrupts

the oceans. Are you more accustomed to viewing one of these in particular? How do these maps influence your

perception of the world?

18. Take a look through pages 12-13 in Goode’s World Atlas (if you have the 23rd edition, pages xvi and xvii). These

pages describe and show examples of the main map projections used in the atlas. List one benefit and one

drawback specific to Goode’s Interrupted Homolosine Equal Area Projection (also shown above in Figure 6).

19. What is a map projection?

Types of Maps

Look over the thematic map types on pages 14-15 (or xviii-xix in newer edition) and types of map projections on pages

12-13 (xvi and xvii) in Goode’s World Atlas to answer the following:

20. What type of thematic map are the temperature maps on pages 32-33 (or in 23rd edition, pages 22-23)? Select

one of the following:

a. Choropleth map

b. Isoline map

c. Area class map

21. On page 39 (or page 30 in 23rd edition), examine the map of carbon dioxide emissions.

a. What type of thematic map is this?

b. What does the size of the circle represent?

c. What does the color of the circle represent?

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22. On the Rock Type map pp. 96-97 (or in 23rd edition, the Geology map on pages 42-43), would the Colorado

Plateau appear larger or smaller at a scale of 1:1,000,000?

23. Looking at the Rock Type of the US map on pages 96-97 (42-43 in newer edition), can you discern which rock

type is more common at the surface (igneous, metamorphic, or sedimentary)?

Isoline and Topographic Maps

A topographic map displays the relative positions and elevations of physical features on the Earth’s surface. The

United States Geological Survey (USGS) publishes topographic maps for the United States in a variety of sizes

and scales (ranging from 1:24,000 to 1:1,000,000). The most commonly used scale of a topographic map is

1:24,000, which covers an area measuring 7.5 minutes latitude by 7.5 minutes longitude and is referred to as a

7.5-minute quadrangle.

An isoline is a line that connects points of equal value, and contour lines are a specific type of isoline that

connect points of equal elevation. Contours are usually printed in brown on topographic maps, and index

contours are heavier brown lines usually marked with the elevation. The contour interval is the change in

elevation between contours, and varies from map to map.

Figure 5 Contour lines and a corresponding landscape.

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Contour Line Characteristics:

• A contour line represents only one elevation.

• Contour lines do not divide or split.

• Contour lines do not end. They may run off maps that represent only a small portion of the landscape.

• Contours are closer together on steep slopes and farther apart on gentler slopes. On vertical slopes,

contour lines will overlap, but they never cross each other.

• Contour lines bend upstream into an inverted “V” when crossing streams, and bend downslope when

crossing ridges.

• Hatchured contours indicate a depression. The hatchured lines have small tick marks on the downhill

side.

Examine the map of Lake Contouria with elevational points. The 170 foot contour has already been drawn. Draw the

remaining contour lines at intervals of 10 feet. Be sure that all points with a lower elevation than the contour line you

are drawing are on the downhill side of the line. Use a pencil and draw lightly until you are sure the contour positions

are correct, then darken the lines. The inverted “V”s should coincide with the stream channels.