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Chapter 2: Portraying Earth
McKnight’s Physical Geography: A Landscape Appreciation,
Tenth Edition, Hess
Portraying Earth
• The Nature of Maps
• Map Scale
• Map Essentials
• The Role of Globes
• Map Projections
• Families of Map Projections
• Isolines
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Portraying Earth
• GPS—Global Positioning System
• Remote Sensing
• GIS—Geographic Information Systems
• Tools of the Geographer
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The Nature of Maps
• 2-dimensional representation of Earth’s surface
• Show 4 key properties of a region– Size– Shape– Distance– Direction
• Maps are imperfect, since Earth is a sphere
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Figure 2-2b
Map Scale
• Maps are always smaller than the area they represent
• Map scales are necessary to understand realistic distances on map
• Scale is relationship between area on map and area on Earth
• Three primary types– Graphic
– Fractional
– Verbal
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Figure 2-3
Map Scale
• Large versus small map scales
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Figure 2-4
Map Essentials
• Need several properties of maps to help with interpretation:– Title– Date– Legend– Scale– Direction– Location– Data Source– Map Projection
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Figure 2-5
The Role of Globes
• Advantages of Globes– Maintains correct geographic
relationships between points– Can accurately represent spatial
relationships between points on Earth
• Disadvantages of Globes– Only can see a hemisphere at a
time– Large and bulky– Cannot contain much detail
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Figure 2-6
Map Projections
• Challenge of the cartographer (“mapmaker”)– Combine geographic exactness of globe with convenience of
flat map
• Definition of map projection
• Principle behind map projections
• Two primary types– Equivalent—ratio of areal size on map and Earth is the same– Conformal—shape of locations on the map is the same as on
Earth
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Map Projections
• Equivalence versus conformality dilemma
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Figure 2-10
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
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Figure 2-7
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
– An example is an orthographic plane projection (Figure 2-13)
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Figure 2-9
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
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Figure 2-8
Families of Map Projections
• Pseudocylindrical Projections– A mix of conformal and
equivalent
– Central parallel and meridian cross at right angles
– Oval shaped; distortion increases as you move away from the center
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Figure 2-11
Families of Map Projections
• Interrupted Projections– Minimize distortion
– Discontinuous map, shapes and sizes maintained
– Typically oceans are distorted; land masses maintain original shape and size
– Goode’s projection
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Figure 2-14
Isolines
• Definition
• Many types– Isobar: line of constant
pressure
– Isotherm: line of constant temperature
– Isohyet: line of constant rain
– Isoamplitude: line of constant wave amplitude
• Construction steps/rules
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Figure 2-16
Isolines
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800
700600 500 400
300
Isolines
• Topographic Maps– Show elevation
contours– Contour lines– Lines closer together
represent steeper terrain
– Often used in geography
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Figure 2-15
Isolines
• Topographic Maps– Show elevation
contours– Lines closer together
represent steeper terrain
– Often used in geography
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Figure 2-15
GPS—Global Positioning System
• Global navigation satellite system for determining location on Earth’s surface
• Wide Area Augmentation System (WAAS)
• Continuously Operating GPS Reference Stations (CORS)
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Figure 2-19
Remote Sensing
• Measurement by a device not in contact with Earth’s surface
• Common types include:– Aerial Photographs– Orthophoto maps– Visible Light and Infrared
(IR) Scanning– Thermal IR scanning– Radar and Sonar– Many others
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Aerial Photography—Figure 2-20
Remote Sensing
• Orthophoto maps– Photographic maps that
are multicolored and distortion free
– Useful in low-lying coastal regions to show marsh topography
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Figure 2-21
Remote Sensing
• Visible light and IR scanning– Based off of visible light and
IR part of electromagnetic spectrum (Figure 2-22)
– Shows “false color”
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Figure 2-23Figure 2-22
Remote Sensing
• Radar Imagery– “Radio Detection and Ranging”– Useful for identifying atmospheric moisture
• Sonar Imagery– “Sound Navigation and Ranging”– Permits underwater imaging
• Thermal IR scanning– Scans in the thermal IR part of spectrum– Shows images based on temperature– Often utilized in meteorology
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GIS—Geographic Information Systems
• Computer systems used to analyze and display spatial data
• Layers of data used in mapping
• Requires high powered computing to process multiple maps
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Figure 2-29
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
• Ultimate goal: “To better understand Earth.”
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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
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Summary
• 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
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Summary
• 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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