The Global Positioning System (GPS) Brief History of Navigation PreHistory - Present: Celestial Navigation Ok for latitude, poor for longitude until accurate clock invented ~1760 13 th Century: Magnetic Compass 1930’s: Radar and Inertial Nav 1940’s: Loran-A
A 3rd range constrains user to 1 of the 2 points.
1 range puts user on the spherical face of the cone.
Intersecting with a 2nd range restricts user to the circular arcs.
Pictures courtesy http://giswww.pok.ibm.com/gps