Finding Locations on Earth

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					Finding Locations on Earth

    Earth and Space Science
          Ms. Pollock
           2008-2009
     Finding Locations on Earth
• Earth nearly a perfect sphere
• Axis of rotation used for reference points
• Reference points geographic North and South
  Poles and the equator
• Hemispheres created
                  Latitude
• Positions north and south of equator
• Parallels – circles running east and west
  parallel to the equator
• Latitude – angular distance north or south of
  the equator
• Measured in degrees
• Equator 0 latitude
• Poles 90 latitude
                    Latitude
• 1 latitude = 111 km
• Parallels north of
  equator labeled N,
  parallels south of
  equator labeled S
• Each degree divided
  into 60 minutes (1.85
  km)
• Each minute divided
  into 60 seconds
                 Longitude
• How far east or west along a parallel
• Meridian – a semicircle that runs from pole to
  pole
• Prime meridian selected by international
  agreement to pass through Greenwich,
  England
• Longitude – angular distance east or west of
  the prime meridian
Longitude
     • All locations east of
       prime meridian 0 to
       180 E
     • All locations west of
       prime meridian 0 to
       180 W
     • Distance between
       meridians varies
       because meridians end
       at poles
                   Great Circles
• Any circle that divides the
  globe into halves
• Meridians directly across
  globe from each other
• Equator only line of
  latitude that is a great
  circle
• Shortest distance
  between two points on
  the globe
            Finding Direction
• Magnetic compass
  – Uses Earth’s magnetic properties
  – Compass needle points toward geomagnetic north
    pole
  – Geomagnetic poles different from geographic
    poles
Magnetic Declination
          • Angle between
            geomagnetic north pole
            and geographic north
            pole
          • Measured east and
            west of poles
   The Global Positioning System
• Global network of 24 satellites that transmit
  radio waves to Earth
• First NAVSTAR, 1978
• GPS receiver signaled by three satellites
  calculating latitude, longitude, and altitude
• Personal receivers accurate to within 10-15 m
  of location
• Commercial receivers accurate to within cm

				
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posted:9/13/2012
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