Models of the Earth

Finding Locations on the Earth Globe: spherical representation of the

earth’s surface No corners, no top, no bottom as

reference points

Use rotation of Earth on it’s axis as reference point

North and South Geographic Poles Equator located halfway between poles

Latitude Parallels: set of circles around the Earth

going east to west and separated north to south

LatitudeLatitude: the angular distance north or south of the equator -equator is zero degrees-measured in degrees

from equator

Parts of Latitude 0o to 90o from equator to North pole –

labeled N 0o to 90o from equator to South pole –

labeled S Each degree broken into 60 parts called

minutes

Parts of Latitude Degrees symbol = o

Example: 45o says 45 degrees Minutes symbol = ‘

Example: 30’ says 30 minutes Seconds symbol = “

Example 23” says 23 seconds

Parts of Latitude Washington D.C.

38o53’51”N reads 38 degrees 53 minutes 51 seconds north

(Image rounded to degrees)

Longitude Meridians: intersections to determine

east-west locations on latitude Measured in degrees, minutes, and

seconds too Prime meridian agreed to be 0o – runs

through Greenwich, England

LongitudeLongitude: the angular distance east or west of the prime meridian -prime meridian is zero degrees-- measured in degrees

from prime meridian

Parts of Longitude 0o to 180o east of prime meridian –

labeled E 0o to 180o west of prime meridian –

labeled W Distance between degrees depends on

location on Earth

Parts of Longitude Degrees symbol = o

Example: 45o says 45 degrees Minutes symbol = ‘

Example: 30’ says 30 minutes Seconds symbol = “

Example 23” says 23 seconds

Parts of Longitude Washington D.C.

77o0’33”W reads 77 degrees 0 minutes 33 seconds west

(Image rounded to degrees)

Great Circles Great circle: any circle that divides the

globe into halves Any circle formed by two meridians on

opposite sides of globe

Finding Direction Magnetic compass: indicates direction

by responding to earth’s natural magnetic properties

Earth’s imaginary magnet is at an angle to the earth’s axis of rotation

Finding DirectionThe points on the earth’s surface just above the poles of the imaginary magnet are called geomagnetic poles

Geomagnetic and geographic poles are in different locations

Finding DirectionMagnetic declination: the angle between the direction of the geographic pole and the direction which the compass points

Magnetic pole shift http://www.youtube.com/watch?v=Rmc

8U9zWN00

Finding DirectionThe geographic north pole is called true north.

Mapping the Earth’s SurfaceCartography: the science of map makingMap: a flat representation of the earth’s

curved surface

Map Projections A flat map surface that covers a 3D

curved surface is called a map projection

Map ProjectionsMercator projection:

wrapping a cylinder of paper around a lighted globe

Map ProjectionsGnomonic projection

(polar): a sheet of

paper only touches a lighted globe at one point

Map Projections Gnomonic projection

Helpful for air navigation cause a straight line indicates part of a great circle

Map ProjectionsConic Projection: a

paper cone placed over a lighted globe so the axis of the cone aligns with the axis of the globe

Cone touches the globe along one parallel of latitude

Map ProjectionsPolyconic projection:

a series of conic projections used to map a number of neighboring areas

Reading a MapSymbols needed to read a map

Legend: a list of symbols and their meanings

Direction: usually indicates north somewhere on map

Scale: indicates the relationship between distance as shown on map and actual distance