1. Maps as Models of the Earth
Chapter 2

2. Section 1
You Are Here
Map = a model or representation of the Earth’s surface.
What Does the Earth Really Look Like?
The Greeks thought the Earth was round 2,000 years before Columbus made his voyage
A Greek mathematician in 240 B.C. calculated the Earth’s circumference using geometry & observations of the sun
He was only 15% off which is not bad for a time with no computers or satellites.

3. Finding Direction on Earth
Section 1
Finding Direction on Earth
reference point = a fixed place on the Earth’s surface from which direction & location can be described
The Earth is round & has no top, bottom, or sides for people to use as a reference point
The Earth does turn on its axis.
At either end of the axis is a geographic pole (North & South Pole). We use these poles as reference points when describing direction & location on the Earth.

4. Cardinal Direction Section 1
cardinal directions = north, south, east & west
Using a Compass
One way to determine north is by using a magnetic compass.
A compass points to the magnetic north pole
The Earth has two different sets of poles – the geographic poles & the magnetic poles.
They are in slightly different locations from each other.

5. True North & Magnetic Declination
Section 1
True North & Magnetic Declination
True North = the geographic north pole (because it doesn’t change)
Magnetic Declination = the angle of correction used to find true north from magnetic north
Finding Location on the Earth
To find a house you have an address. Cities & islands have “addresses” we use latitude & longitude to create global addresses.

6. Section 1
Latitude
Parallels – Imaginary lines drawn around the Earth parallel to the equator (also called lines of latitude)
Equator = a circle halfway between the poles that divides the Earth into the Northern & Southern Hemispheres
Latitude = is the distance north or south, measured in degrees, from the equator.
Picture on 37 helps with understand this

7. Section 1
Longitude
Meridians – Imaginary lines that pass through the poles (also called lines of longitude)
Longitude = is the distance east & west, measured in degrees, from the prime meridian
Prime Meridian = the line that represents 0o longitude (it passes through Greenwich, England)
The prime meridian does not completely circle the globe like the equator does. It runs from the North Pole through Greenwich, England to the South Pole.
Picture on page 38 makes it more understandable

8. Using Latitude & Longitude
Section 1
Using Latitude & Longitude
Points on the Earth’s surface can be located using latitude & longitude. (A grid system:)

9. Mapping the Earth’s Surface
Section 2
Mapping the Earth’s Surface
The Earth is a globe so a globe is a more accurate model of the Earth then a flat map.
But a globe is not the most useful model to use when studying the Earth’s surface.
A globe doesn’t show details.

10. Section 2
A Flat Sphere?
When you transfer information from a curved surface to a flat surface, you lose some accuracy.
Distortions – changes occurring in the shapes & sizes of landmasses & oceans
These distortions make some landmasses appear larger than they really are.
Direction & distances can also be distorted

11. Map Projections Section 2
All flat maps have some amount of distortion.
A map showing a smaller area, such as a city, has much less distortion than a map showing a larger area, such as the entire world.

12. Mercator Projection Section 2
Mercator Projection = a map projection that results when the contents of the globe are transferred onto a cylinder of paper
On Mercator projections the lines of latitude are parallel horizontally while longitude are parallel and equally spaced apart vertically
On many maps Greenland is shown to be as big as Africa when in reality Africa is 15 times larger than Greenland.
Page 41

13. Conic Projection Section 2
Conic Projection = a map projection that is made by transferring the contents of the globe onto a cone. (the cone is then unrolled to form a flat plane)
There are more distortions for landmasses that have more area north to south (South America) then land masses that have more area east to west (US)
Page 42

14. Azimuthal Projection Section 2
Azimuthal Projection = a map projection that is mad by transferring the contents of the globe onto a plane
On an azimuthal projection, the plane touches the globe at only one point. There is little distortion at that point but as you move away from that point the distortion increases.
Page 42

15. Modern Mapmaking Section 2
Mapmaking has changed more since the beginning of the 1900s than during any other time in history. This is due to technological advances.
Airplanes & Cameras
Aerial Photographs = photographs from the air.
The photographs are important in helping mapmakers make accurate maps.
Remote Sensing
Remote Sensing = gathering information about something without actually being there (i.e. satellites)
Satellites have allowed mapmakers to map the surface of the Earth more accurately.

16. Information Shown on Maps
Section 2
Information Shown on Maps
Title – tells you what area is being shown on the map or gives you information about the subject of the map
Compass Rose – shows you how the map is positioned in relation to true north.
Legend – a list of the symbols used in the map & their explanations
Date – gives the time at which the information on the map was accurate.

17. Information Shown on Maps
Section 2
Information Shown on Maps
Map’s scale – shows the relationship between the distance on the Earth’s surface & the distance on the map.
Graphic Scale – is like a ruler. The distance on the Earth’s surface is represented by a bar graph that shows units of distance.
Verbal Scale – is the phrase that describes the measure of distance on the map relative to the distance on the Earth’s surface.
Representative Fraction – a fraction or ratio that shows the relationship between the distance on the map & the distance on the Earth’s surface. It is unit less, meaning it stays the same no matter what units of measurement you are using.
Page 44

18. Topographic Maps Section 3
Topographic Map = a map that shows surface features, or topography, of the Earth.
These maps show natural features, such as rivers, lakes, & mountains
They show features made by humans, such as cities, roads, & bridges.
Elevation is also shown on these maps.
Elevation = the height of an object above sea level

19. Elements of Elevation Section 3
In the US the unit used on Topographic map is feet.
Contour Lines
Contour Lines = lines that connect points of equal elevation
Contour Interval
Contour Interval = the difference in elevation between one contour line & the next.
Relief = the difference in elevation between the highest & lowest points of the area being mapped.

20. Contour Interval Section 3
The spacing of contour lines also indicates slope. Contour lines that are close together, with little space between them, usually show a steep slope. Contour lines that are space far apart represent a gentle slope.
Index Contour
Index Contour = a darker, heavier contour line (it is usually every fifth line) & is labeled by elevation.

21. Reading a Topographic Map
Section 3
Reading a Topographic Map
Different colors are also used to represent different features of the Earth’s surface.
buildings, roads, bridges, & railroads are black
Contour lines are brown
Major highways are red
Cities & towns are pink
Bodies of water, such as rivers lakes & oceans, are in blue
woodland areas are in green

22. The Golden Rules of Contour Lines
Section 3
The Golden Rules of Contour Lines
Contour lines never cross. All points along a contour line represent a single elevation
The spacing of contour lines depend on slope characteristics. Closely spaced contour lines represent a steep slope. Widely space contour line represent a gentle slope.
Contour lines that cross a valley or stream are V- shaped. The V points toward the area of higher elevation. If a stream or river flows through the valley, the V points up stream.

23. The Golden Rules of Contour Lines
Section 3
The Golden Rules of Contour Lines
Contour lines form closed circles around the tops of hills, mountains, & depressions. One way to tell hills & depressions apart is that depression are marked with short straight lines inside the circle, pointing downslope toward the center of the depression.