Chapter 2: The Geographer’s Tools - Cloud Object Storage · Chapter 2: The Geographer’s ... Copyright © 2014 John Wiley & Sons, Inc. All rights reserved. ... Copyright © 2014

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Discovering Physical GeographyThird Editionby Alan Arbogast

Chapter 2:

The Geographer’s Tools

Copyright © 2014 John Wiley & Sons, Inc. All rights reserved.

• Great circles

• Small circles

The Geographic Grid


The Geographic Grid: Latitude

• Equator as reference

• Northern and Southern

Hemispheres

• Parallels are

lines of latitude

• Three zones: low, middle,

and high latitudes


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• Prime Meridian as reference

• Meridians are

lines of longitude

• Eastern and western

halves

The Geographic Grid: Longitude


Maps –The Basic Tool of Geographers

• Cartography focuses on ways to display spatial information so it can be used and understood efficiently

• A thematic map shows one or a limited number of types of information, or themes—

for example, a map of rainfall and/or temperature

• A globe is the most visually complete and accurate way to represent the Earth


Map Projections

• Three-dimensional Earth on a two-dimensional surface

• Inevitable distortion:

shape or size

• Projections preserve either shape or size, but not both


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Mercator• corrects the

relative shape of landmasses

• distorts the size of landmasses near the poles

• lines of latitude are at right angles

Map Projections: Conformal


Map Projections: Equivalent

Albers Equal-Area• Corrects the relative

size of landmasses

• Distorts the of shape of landmasses near the Poles and Equator

• Lines of latitude are curved


Map Scale

Relates the size and/or distance between features on a map to the actual features in the real world

•Scale depictions– Written (verbal) scale

One Inch = 2000 Feet

– Representative fraction1:24000 or 1/24000

– Graphic scale or bar scale

0 5Miles


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Map Scale

• Large scale– Small geographic

areas

– Greater level of detail

• Small scale– Large geographic

areas

– Limited level of detail


Isoline Maps

• Isolines are lines connecting points of equal value on a map

• Various kinds of isolines– Isobars: points of equal atmospheric pressure

– Isotherms: points of equal air temperature

– Isohyets: points of equal precipitation amounts

– Isopachs: points of equal sedimentary thickness

– Contours: points of equal elevation


Isoline Maps

Drawing Isolines• Start with a map of

temperatures (a)

• Isotherms at 2 intervals are drawn (b) and (c)

• Shading is added to show the geographic patterns of temperature over the upper Midwest (d)


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Digital Technology in Geography: Remote Sensing

• New approach to spatial analysis

• Involves measuring properties of the environment without direct contact

• Started with: Aerial Photography– Systematic photographs taken in succession over

linear flight lines at set intervals of time

– Limiting because complete sets of photographs of large regions were only taken at irregular intervals of time


Digital Technology in Geography: Remote Sensing

• Later technology: satellite imagery– Sun-synchronous orbit

• Keeps pace with Sun’s westward progress

– Geostationary orbit• Permanently remains

in one place above Earth


• System of satellites and receivers

• Determine location in the geographic grid 24 satellites orbit Earth

every 12 hours

• Pseudorandom Code (PSR) transmits in sequence of pulses

Digital Technology in Geography: Global Positioning Systems (GPS)


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Digital Technology in Geography: Global Positioning Systems (GPS)

Triangulation• Artificial constellation of

satellites as locationalreferences

• Signals from up to four satellites overlap to pinpoint location


Digital Technology in Geography: Geographic Information Systems (GIS)

System for storing, analyzing, and manipulating spatially referenced data

•GIS databases consist of series of individual data layers

•A data layer contains measurements for a specific geographic variable, such as

– Vegetation, soils, road networks, municipal boundaries, and hydrology


Digital Technology in Geography: Geographic Information Systems (GIS)

• Each layer is assigned a variety of detailed attributes

• Each layer exists as a distinct unit

• For analysis or display, layers are overlaid or combined


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Chapter 2: The Geographer’s Tools - Cloud Object Storage · Chapter 2: The Geographer’s ... Copyright © 2014 John Wiley & Sons, Inc. All rights reserved. ... Copyright © 2014