1. Chapter 2: Portraying Earth

2. What’s Your Perspective?

3. Ptolomy’s “World” Map circa 150 A.D.

4. World Maps from the 1500’s

5. The Nature of Maps Geographical illustration
2-D representation of Earth’s surface
Show 4 key properties:
Size
Shape
Distance
Direction
All maps are imperfect, since Earth is a sphere
Mental maps
Figure 2-2b

6. Map Scale Maps are always smaller than the area they represent
Figure 2-3
Maps are always smaller than the area they represent
Scale is the relationship between area on map to same area on Earth
3 types
Fractional
Ratio or fraction to compare map distance to Earth distance
Graphic
Line marked off with distances
Verbal
Words tell ratio of map distance to Earth distance
Figure 2-4

7. Map Scale Large vs. small map scales Large scale Small scale
Figure 2-4
Large vs. small map scales
Large scale
Large representative fraction (small denominator)
Shows smaller area, but with more details
Small scale
Small representative fraction (large denominator)
Shows larger area, but with less details

8. 8 Map Essentials Title Date Legend Scale Direction Location
Figure 2-5
Title
Date
Legend
Scale
Direction
Location
Data Source
Map Projection

9. The Role of Globes Advantages of Globes Disadvantages of Globes
Maintains correct geographic relationships between points
Accurately represents spatial relationships between points on Earth
Essentially, no distortion
Disadvantages of Globes
Only can see 1 hemisphere (half) at a time
Large and bulky
Cannot contain much detail
Figure 2-6

10. Map Projections Cartography: construction & production of maps
Figure 2-2d
Cartography: construction & production of maps
Cartographer: a person who makes maps
Challenge:
Combine geographic exactness of globe with convenience of flat map
Fundamental Problem: minimize distortion while transferring from a rounded to a flat surface
Definition of map projection
System to transform a curved surface to a flat display

11. Map Projections 2 primary types
Equivalent—ratio of areal size on map & Earth is the same
Distorts shapes
Conformal—location shape on the map is the same as on Earth
Distorts sizes
Figure 2-10

12. Families of Map Projections
Cylindrical Projections
“Wrap” the globe in a cylinder of paper
Paper tangent to Earth at equator
Conformal projection
Mercator projection is most famous
Invented over 400 years ago for ocean navigation
Distortion increases as you move poleward
Latitudes spaced farther apart poleward to minimize distortion
Figure 2-7

13. Families of Map Projections
Plane Projections
Project globe onto a paper that is tangent to globe at some point
Displays one hemisphere well
Equivalent projection
Figure 2-9

14. Families of Map Projections
Conic Projections
Project the map onto a cone tangent to or intersecting the globe
Principal parallel
Good for mapping small areas on Earth
Impractical for global mapping
Figure 2-8

15. Families of Map Projections
Pseudocylindrical Projections
Mix of conformal and equivalent
Central parallel and meridian cross at right angles
Oval shaped; distortion increases as you move away from the center
Figure 2-11

16. Families of Map Projections
Interrupted Projections
Minimize distortion on continents
Discontinuous map, shapes and sizes maintained
Typically oceans are distorted; land masses maintain original shape and size
Figure 2-14

17. Isolines Definition Many types Lines that join points of equal value
Isobar: line of constant pressure
Isotherm: line of constant temperature
Isohyet: line of constant precipitation
Figure 2-16

18. Isolines
800
600
500
700
400
300

19. Isolines
Figure 2-15
Rules:
Always closed lines (no ends)
Show gradations in quantities
Lines do not cross
Interval: numeric difference between individual isolines
Index contour: usually every 4th or 5th line is bolder & marked with that line’s elevation
Used to calculate intervals
Topographic Maps
Contour lines: lines connecting points of equal elevation
Lines closer together represent steeper terrain

20. GPS—Global Positioning System
Global navigation satellite system for determining location on Earth’s surface
Network of “active” satellites
Several older backup satellites
Wide Area Augmentation System (WAAS)
Continuously Operating GPS Reference Stations (CORS)
Figure 2-19

21. Aerial Photography—Figure 2-20
Remote Sensing
Measurement by a device not in contact with Earth’s surface (balloon, airplane, rocket, satellite)
Common types include:
Aerial Photographs
1st form of remote sensing
Oblique: camera angle less than 90°
Vertical: camera angle perpendicular to Earth’s surface
Photogrammetry: science of mapping from aerial photographs
NASA Connect Remote Sensing
Aerial Photography—Figure 2-20

22. Remote Sensing Stereoscopy Uses overlapping vertical photographs
Requires 2 vertical aerial photographs that align & overlap at least 60%
Produces 3-D appearance
Figure 2-A (a & b)

23. Remote Sensing Orthophoto maps
Photographic maps that are multicolored & distortion free
Precise distance measurements
Useful in low-lying coastal regions to show marsh topography
Figure 2-21

24. Remote Sensing Visible light & IR scanning
Based off of visible light and IR part of electromagnetic spectrum (Figure 2-22)
Shows “false color”
Figure 2-23
Figure 2-22

25. Remote Sensing Radar Imagery Sonar Imagery Thermal IR scanning
Helps identify atmospheric moisture
Sonar Imagery
Permits underwater imaging
Thermal IR scanning
Scans in thermal IR part of spectrum
Shows images based on temperature

26. GIS—Geographic Information Systems
Figure 2-29
Computer systems used to store, analyze and display spatial data
Use layers of data for mapping

27. GIS—Geographic Information Systems
Google Maps
Sarpy County Internet Mapping Service
Douglas-Omaha GIS
Google Earth
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28. Tools of the Geographer
Vast array of maps, remotely sensed satellite imagery, and computer applications
Difficult to determine the best way to use all of this information
Some tools better at identifying features on Earth than others
Computer Technology
Improved speed and data handling
Greatly reduced time in producing maps
Allows cartographers to examine different map layouts
Ultimate goal: “To better understand Earth.”

29. Summary Maps are essential to portray features on Earth’s surface
Need a map scale to identify how a map relates to the actual surface features on Earth
Many other map properties are essential to interpreting a map
Globes have several advantages and disadvantages
Representing Earth in 2 dimensions can be done through map projections
Many different map projections exist
Dilemma of equivalent versus conformal
Plotting isolines on a map can help with interpretation of features on the map
The global positioning system (GPS) helps to identify location on Earth’s surface
Remote sensing is a measurement of Earth’s surface from a system not on Earth’s surface
Many different remote sensing instruments exist, including satellite, radar, and sonar
GIS are computer systems used to analyze and display spatial data, often in layers
The geographer has many tools, but the ultimate goal is “To better understand Earth.”