Chapter 2: Representations of Earth

Physical Physical GeographyGeographyNinth EditionNinth Edition

Robert E. Gabler

James. F. Petersen

L. Michael Trapasso

Dorothy Sack

2.1 Location on Earth

•Maps and Mapmaking•History

•Language of location

•Cartography

U.S. Landforms in 1954

2.1 Location on Earth

• Size and Shape of Earth– Eratosthenes– Oblate spheroid

• Equator bulges outward due to earth’s rotation.

• Equator (12,758 km, 7927 miles) • Pole to pole (12,714 km, 7900

miles)

– Mt. Everest (29,035 feet)– Mariana Trench (36,200 ft)

2.1 Location on Earth

• Globes and Great Circles– Great Circle– Hemispheres– Circle of illumination– Small circle– Great circle routes

2.1 Location on Earth

• Latitude and Longitude– Coordinate system

2.1 Location on Earth

• Measuring Latitude– Reference points: North

and South Pole– Reference Line: Equator– Latitude

• degrees North or south of equator

• Lines that run east and west

– sextant

2.1 Location on Earth

• Measuring Longitude– Reference Line: Prime

Meridian– Longitude

• degrees East or West of Prime Meridian

• Lines that run north and south from pole to pole

2.2 The Geographic Grid

• Geographic Grid: Lines of Latitude and Longitude– East to West lines are

also called parallels– North to South lines are

also called Meridians

2.2 The Geographic Grid

• Longitude and Time– Time Zones: relationships

between longitude, Earth’s rotation, and time.

– Solar noon– Central meridian– Greenwhich Mean Time

(GMT), Zulu time, Universal time (UTC)

World Time Zones

2.2 The Geographic Grid

• International Date Line– Generally follows 180th

meridian– Jogs to separate Alaska

and Siberia as well as some pacific Island groups

– Going east across IDL, subtract a day

– Going west across IDL, add a day.

2.2 The Geographic Grid

• U.S. Public Lands Survey System– Also called Township

range system– Divides towns based on

north-south lines called meridians and east-west lines called base lines.

2.2 The Geographic Grid

• Township: square plot 6 miles on a side.– Divided into 36 sections

of 1 square mile.– Sections divided into

quarter sections– Quarter-quarter sections– Forties (each with an

area of 40 acres.

Public Lands Survey System

2.2 The Geographic Grid

• Global Positioning System– Uses a network of

satellites.– Determines latitude,

longitude, and elevation.

2.2 The Geographic Grid

• Global Positioning System– Uses a network of

satellites.– Determines latitude,

longitude, and elevation.

2.3 Maps and Map Projections

• Advantages of Maps– Spatial relationships– Enormous amount of

information– Limitless possibilities

2.3 Maps and Map Projections

• Limitations of Maps– Impossible to present a

“spherical” planet on a flat surface.

– All flat maps are distorted.

2.3 Maps and Map Projections

• Properties of Map Projections– Planar– Cylindrical– Cone

2.3 Maps and Map Projections

• Shape– Conformal maps: correct

shape but incorrect size.– Example: Mercator

Projection• Compare Greenland and

South America• South America is 8 times

larger.

2.3 Maps and Map Projections

• Size– Equal-area maps: correct

size but incorrect shape.– Essential when examining

spatial distribution of any element:

• People• Churches• Cornfields• Volcanoes

2.3 Maps and Map Projections

• Distance– No flat map depicts

correct distance– On small maps,

distances errors are minor

– Equidistance: constant scale

Direction

2.3 Maps and Map Projections

• Examples of Map Projections– Mercator Projection

2.3 Maps and Map Projections

• Examples of Map Projections– Gnomonic Projection– Conic Projection

2.3 Maps and Map Projections

• Compromise Projections

2.3 Maps and Map Projections

• Map Basics– Title– Legend– Scale

• Verbal scale• Representative fraction• Graphic (bar) scale

– Distance

2.3 Maps and Map Projections

• Scale– Small scale

• Large areas in a relatively small area

• Little detail• Large denominators

– Large scale• Small areas in greater detail• Smaller denominators

2.3 Maps and Map Projections

• Direction– Magnetic north– Magnetic field– Magnetic declination– Isogonic map

2.3 Maps and Map Projections

• Isogonic map

2.4 Displaying Spatial Data and Information on Maps

• Thematic Maps– One feature (or a few related ones)

• Climate, Vegetation, Soils, Earthquakes, Tornadoes

– Discrete data• Point, area, or line

• Examples: school, roads, hurricane path

• Regions: discrete areas with common characteristics

– Continuous data• Element exists at all points on earth

• Examples: elevation, air temperature, air pressure

• Discrete and Continuous data

2.4 Displaying Spatial Data and Information on Maps

• Direction– Magnetic north– Magnetic field– Magnetic declination– Isogonic map

2.4 Displaying Spatial Data and Information on Maps

• Topographic Maps– Contour lines: lines that

connect points of equal elevation

2.4 Displaying Spatial Data and Information on Maps

• Gradient– Steeper (stronger)

gradient• lines are closer together• Example: steeper slope;

A to top of hill

– Smaller (weaker) gradient

2.4 Displaying Spatial Data and Information on Maps

2.5 Modern Mapping Technology

• Digital Mapmaking– Digital elevation models

(DEM’s): computerized, 3-D view of topography.

– Vertical exaggeration

2.5 Modern Mapping Technology

• Geographical Information Systems– Map layers– Data

• Geocoding: entering spatial data in relation to grid coordinates

• Attributes: specific features (e.g. name of river)

– Registration and Display

• Visual Models: Salt Lake City, Utah

2.4 Displaying Spatial Data and Information on Maps

• Visual Models: Cape Town, South Africa

2.4 Displaying Spatial Data and Information on Maps

• GIS in the Workplace

2.4 Displaying Spatial Data and Information on Maps

2.5 Remote Sensing of the Environment

• Remote Sensing: collection of information and data about distant objects or environments.– Digital image– Spatial resolution– Pixels– Megapixels

2.5 Remote Sensing of the Environment

• Aerial Photography and Image Interpretation– Oblique– Near Infrared (NIR)

• Light reflected off of surfaces, not radiated heat.

2.5 Remote Sensing of the Environment

• Specialized Techniques– Thermal Infrared (TIR)

• Patterns of heat and light• Day or night• Many weather satellites

2.5 Remote Sensing of the Environment

• Specialized Techniques– Radar (Radio Detection And Ranging)

• Transmits radio waves and reads reflected energy signal

• Side-Looking Airborne Radar (SLAR)

2.5 Remote Sensing of the Environment

• Weather Radar systems– produce map-like images of

precipitation– Penetrates clouds– Day or night– Reflects off raindrops (or other

precip.) producing a signal– Doppler radar – precip.

Patterns, direction of storm and speed of storm

2.5 Remote Sensing of the Environment

• Multispectral Remote Sensing Applications– Using and comparing

more than 1 type of image

– Example: radar and TIR image

Physical Geography

End of Chapter 2: Representations of Earth