Geographic Location & Time Lab 1

Concepts The Earth’s Grid Time and Time Zones Latitude/parallels Longitude/meridians Prime Meridian, Equator Great and small circles Time and Time Zones International Date Line

Grid System: Latitude & Longitude a.k.a “Parallels” Each line runs parallel to all the others. They are equally spaced apart and never cross. 0o = Equator Maximum extent 90oN at North Pole 90oS at South Pole Lines run east to west but measure distance north and south

Grid System: Latitude & Longitude a.k.a “Meridians” Lines converge at the poles 0o = Prime Meridian Maximum extent 180o… also called the International Date Line Lines run north to south but measure distance east and west

Grid System: Latitude & Longitude Degrees are subdivided into minutes and seconds. The more detailed your location information is, the more accurate it is. O = degree symbol ’ = minute symbol ” = second symbol 1 degree = 60 minutes (1o = 60’) 1 minute = 60 seconds (1’ = 60”) Note: minutes and seconds cannot exceed the value of 60. e.g., 75’ is incorrect. Should be written as 1o15’

Grid System: Latitude & Longitude Always label your latitude and longitude! Latitude labels = N or S Longitude labels = W or E Latitude Degrees range from 0o (at Equator) to 90o N or S. Cannot exceed a value of 90. Longitude Degrees range from 0o (at Prime Meridian) to 180o (International Date Line). Between those spots, a location is either W or E of the Prime Meridian. Cannot exceed a value of 180o.

Grid System: Latitude & Longitude When identifying locations… Latitude comes before longitude Get as detailed as possible (at least degrees and minutes). e.g., Atlanta’s location is: 33°45' N, 84°42′ W

Great Circles A sphere divided exactly in half by a plane which passes right through its center. The largest possible circle you could manage to draw on that sphere's surface Despite the curved appearance on flat maps, great circle routes are the shortest distance between two points on Earth.

Small Circles A circle produced by planes passing through a sphere anywhere except through its exact center. Smaller than a great circle (hence the clever name).

Great or Small Circle? You Decide What are meridians? What are parallels? What is unique about the Equator (relative to all other parallels)?

Great Circle: example The shortest path from Atlanta to Tokyo would fly you through Canada, over Alaska, and down the Pacific Rim. You would not pass straight across the US and over the Pacific! Tokyo, Japan Atlanta

Time Standard Time: legal time in an area 24 Standard Time Zones in the world Spaced 15o longitude apart, or 7.5o on each side of a Central Meridian GMT = Greenwich Mean Time a.k.a. UTC = Coordinated Universal Time The Prime Meridian runs directly through Greenwich, England (just outside of London). Time zones are typically referenced from GMT/UTC. “Zulu” time = military time (24 hr clock) based in Greenwich e.g., “1000Z” = 10am in Greenwich e.g., “1500Z” = 3pm in Greenwich EST = Eastern Standard Time

Central Meridians & Time Zones Prime Meridian (0o) EST is based on the 75oW meridian. There are 7.5o longitude on either side of the meridian, making the time zone 15o longitude wide.

Los Angeles Denver Chicago Atlanta Time (con’t) Time is 1 hour earlier when moving East to West Los Angeles Denver Chicago Atlanta PST MST CST EST 5pm 6pm 7pm 8pm W E Note: EST is 5 hours “behind” (earlier) than GMT. If it is 8pm EST, what time is it in Greenwich?

International Date Line 180o meridian (does not have a W or E label, just simply 180o) When crossing W to E, it becomes the previous day When crossing E to W, it becomes the next day 180o Tues. 6 am Mon. 150oE Tuesday 4 am 165oE Tuesday 5 am 165oW Monday 7 am 150oW Monday 8 am West East