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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