How are latitude and longitude used for navigation?

NAVIGATION The science of studying our position on the surface of earth So… If you are lost at sea with only a ship radio, how can you figure out where you are ?

LATITUDE For any given location on the surface of the earth in the Northern hemisphere, the altitude of Polaris is equal to the observer’s latitude

POLARIS

HOW DO WE FIND POLARIS? We use an astrolabe

ALTITUDE OF A STAR The altitude of a star is its height above the horizon

So if the altitude of Polaris is 60 degrees above the observer’s horizon, his latitude is _______________________ 60 degrees North latitude

LONGITUDE To find your longitude you need to know your local time and the time it is at the Prime Meridian, or Greenwich Mean Time (GMT) #hrs X 15 degrees/Hr If your local time is earlier than GMT you are west If your local time is later than GMT your are East

TIME ZONES The earth is divided into 24 time zones each 15 degrees apart based on longitude

Time is based on the motions of the earth For each time zone you pass through as you go west it is one hour earlier For each time zone you pass through as you go east, it is one hour later