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