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