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Chapter 2: Portraying Earth. 2 What’s Your Perspective?

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Presentation on theme: "Chapter 2: Portraying Earth. 2 What’s Your Perspective?"— Presentation transcript:

1 Chapter 2: Portraying Earth

2 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 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 2-3 Figure 2-4

7 Map Scale 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 Figure 2-4

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

9 The Role of Globes Advantages 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 –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 Figure 2-2d

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

18 Isolines

19 Isolines Rules: –Always closed lines (no ends) –Show gradations in quantities –Lines do not cross Interval: numeric difference between individual isolines Index contour: usually every 4 th or 5 th 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 Figure 2-15

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 Remote Sensing Measurement by a device not in contact with Earth’s surface (balloon, airplane, rocket, satellite) Common types include: –Aerial Photographs 1 st 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 SensingNASA Connect Remote Sensing Aerial Photography—Figure 2-20

22 Stereoscopy –Uses overlapping vertical photographs Requires 2 vertical aerial photographs that align & overlap at least 60% Produces 3-D appearance Remote Sensing 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 –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 Computer systems used to store, analyze and display spatial data Use layers of data for mapping Figure 2-29

27 GIS—Geographic Information Systems Google Maps –http://maps.google.com/http://maps.google.com/ Sarpy County Internet Mapping Service –http://maps.sarpy.com/sims20/http://maps.sarpy.com/sims20/ Douglas-Omaha GIS –http://www.dcgis.org/dogis/http://www.dcgis.org/dogis/ Google Earth –http://www.google.com/earth/ index.html#utm_campaign= en&utm_medium=ha&utm_ source=en-ha-na-us-bk- eargen&utm_term= google%20earthhttp://www.google.com/earth/ index.html#utm_campaign= en&utm_medium=ha&utm_ source=en-ha-na-us-bk- eargen&utm_term= google%20earth

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.”


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