Chapter 2: Portraying Earth

The Nature of Maps pg. 27-30

Map - A two-dimensional representation of Earth and the spatial distribution of selected phenomena

o A scaled drawing of a portion of a landscape

A map serves as a substitute for a surface that we wish to portray/studyo Show geographical areas

The larger the map, the more likely it is that it will not be detailed

The smaller the map, the more limited a map is in area

Basic Abilities of Maps:o Distanceo Sizeo Shape in their horizontal spatial relationships

Maps are not perfectly accurateo It is impossible to portray the curved surface of the Earth on a flat piece of paper

Map Essentials pg. 30-31

Map - A form of symbolization, governed by a set of conventions, that aim to communicate a sense of place

Six Groups of Maps:o Climate Maps

Give general information about climate and precipitation

o Economic/Resource Maps Show the types of resources or economic activities in an area

o Physical Maps Illustrate the physical features of an area

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o Political Maps Show state and national boundaries; indicate capitals and major cities

o Road Maps

o Topographic Maps Use contour lines to show shape and elevation of an area

Basic Elements For Maps:o Title – A brief summary of the map’s concepto Date – Time span over which the information was collectedo Legend – Symbols, colors, shading, etc…o Scale – Used to show relative or absolute size between objects on mapo Directiono Locationo Data Sourceo Projection Type

The Role of Globes pg. 31

Globe - A three-dimensional scale model of Earth (terrestrial globe) or other spheroid celestial body

Globe Advantages:o Globes accurately represent spatial relationships of features on Earth’s surfaceo Globes give a more realistic depiction of Earth than flat maps

Globe Disadvantages:o Cumbersome, do not display much detailo Only visible to half of the human eye at a time

Map Projections pg. 31-33

Families of Map Projections pg. 33-35

Isolines pg. 35-36

Isoline - A device for portraying the spatial distribution of some phenomenon. It refers to any line that joins points of equal value of something.

Also known as :o Isarithmo Isogram

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o Isopletho Isometric Line

Elevation Contour Lines - A line on a map joining points of equal elevation

Most isolines signify intangible features as temperature and precipitation, and some express relative values such as ratios or proportions

Important types of Isolines:o Elevation Contour Line-

A line joining points of equal elevation

o Isotherm- A line joining points of equal temperature

o Isobar- A line joining points of equal atmospheric pressure

o Isohyet- A line joining points of equal quantities of precipitation

o Isogonic Line- A line joining points of equal magnetic declination

Basic Characteristics of Isolines:o Isolines are ALWAYS closed lines (they have no end)

o Isolines can never touch or cross one another (with exceptions or special circumstances)

o Isolines have intervals (The difference between one line and the next)

o Isolines close together indicate a steep gradient (rapid change). Isolines far apart indicate a gentle gradient.

Edmund Halley (1656-1742):o English astronomer and cartographero Produced the first published map with isolines in 1700 (showed isogonic lines in the

Atlantic Ocean)

Patterns that are too large/abstract/detailed are often significantly clarified by the use of isolines

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GPS – The Global Positioning System pg. 37-39

GPS - A global navigation satellite system for determining accurate positions on or near Earth’s surface

Developed in the 1970’s/80’s, by the U.S. Department of Defense

The system is based on a constellation of at least 24 high-altitude satelliteso 4-6 satellites will be in view of any position on Earth

Wide Area Augmentation System (WAAS):o Was originally implemented to increase the accuracy of instrument based flight

approaches for airplanes

Continuously Operating GPS Reference Stations (CORS)o Capable of detecting location differences of less than 1 centimeter of latitude,

longitude, and elevationo One way they are used is for the monitoring of slight changes in the ground surfaces

Geographic Information System pg. 45-46

Role of the Geographer pg. 46-47

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