The GRID System

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The GRID System

• LONGITUDES are lines drawn on maps to connect
  the North and South Poles.
•  Longitudes are also called Meridians.
• Some Important Meridians include
• The Prime Meridian Longitude 0o
• also called (Greenwich Meridian).
• International Date Line Longitude 180o

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Longitudes

• Each meridian is half of a great circle.
• Meridians run in a true north-south direction.
• They are spaced farthest apart at the equator but
  converges at the poles.
• Meridians can be used to determine standard time
  at every place on the earth

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Longitudes
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Latitudes

• LATITUDES are lines drawn on maps stretching East
  - West
• Latitudes are also called Parallels.
• Some Important Parallels include
•  Equator (Latitude 0o)
• Tropic of Cancer (Latitude 23.5oN)
• Tropic of Capricorn (Latitude 23.5oS)
• Arctic Circle (Latitude 66.5oN).
• Antarctic Circle (Latitude 66.5oS).

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Latitudes

• Except for the equator, each latitude is a small
  circle.
• Always parallel to one another.
• Always true east-west lines.
• Can be used to determine the climate of places on
  the earths surface.

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Important Latitudes
North Pole
66.5oN
Arctic Circle
23.5oN
Tropic of Cancer
Equator
0o
23.5oS
Tropic of Capricorn
66.5oS
Antarctic Circle
South Pole
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The Geographic Grid

• A mesh of intersecting Latitudes and Longitudes
  on a map produces a Geographic Grid, also called
  a Reference Grid or Graticule.
• The Geographic Grid is used to identify specific
  locations (absolute locations) on the earths
  surface.

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The Geographic Grid
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The Grid System Circles

• Great Circle A plane that passes through the
  center of the earth.
• The Equator and all Meridians are Great Circles.
• The shortest distance between any two points on
  the earth's surface is attained along the arc of
  a Great Circle.
• Small Circles lines that do not pass through the
  center of the earth. All Parallels except the
  Equator are Small Circles.

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Great Circles

• Great Circle - a plane that passes through the
  center of the earth.
• The Equator and all Meridians are great circles.
• The shortest distance between any two points on
  the earth's surface is attained along the arc of
  a Great Circle.

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Small Circles

• Small Circles are lines that do not pass through
  the center of the earth.
• All Latitudes except the Equator are Small
  Circles.