Finding Locations on Earth

1. Finding Locations on Earth Earth and Space Science Ms. Pollock 2008-2009

2. 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

3. 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

4. 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

5. 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

6. 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

7. 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

8. Finding Direction • Magnetic compass • Uses Earth’s magnetic properties • Compass needle points toward geomagnetic north pole • Geomagnetic poles different from geographic poles

9. Magnetic Declination • Angle between geomagnetic north pole and geographic north pole • Measured east and west of poles

10. 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