Longitude and LatitudeEarth is divided into imaginary lines of longitude and latitude measured in degrees (since Earth is spherical). These lines form Earth’s coordinate system and enable us to locate any position on

Earth’s surface.

Directions• Compass = tool that uses Earth’s magnetic field to locate magnetic North

• Label the compass rose with the appropriate directions

S

EW

NE

SESW

NW

Latitude

• Imaginary lines that run horizontally (east-west) across globe

• “Ladder-tude” = look like rungs of a ladder• Also called parallels because equal distances from

each other• North Pole = 90⁰N Latitude (max latitude)• South Pole = 90⁰S Latitude (max latitude)• Equator = 0⁰ Latitude Divides planet into

Northern and Southern Hemispheres • Latitude in the Northern hemisphere is determined

by the altitude of the North Star, Polaris.

Lines of Latitude

Equator

Tropic of Cancer

23.5 N.

Tropic of Capricorn

23.5 S.

Finding Polaris and Ursa Minor• To find the star Polaris and the

constellation Ursa Minor, locate the two end stars in the cup of the "Big Dipper."

• Connect a line through these two stars. This will point to the star Polaris.

• Polaris is in the constellation Ursa Minor. Ursa Minor is better known as the "Little Dipper."

• Polaris will not be an extremely bright star, but it will be located due North.

Longitude

• Imaginary lines that run vertically (north-south) across globe

• Converge at the poles and are widest apart at the equator

• Also called meridians• Prime Meridian = 0⁰ Longitude – runs through

Greenwich, England• International Date Line = 180⁰ Longitude in

Pacific Ocean (max longitude)

To find the difference in hours between local time and Greenwich time:

• Multiply the difference by 15 per hour (The rate at which the Earth rotates)

• If local time is earlier than Greenwich time, then your position is West Longitude.

• If local time is later than Greenwich time, then your position is East Longitude.

Example1.There is a 5 hour time difference between New York City and Greenwich, England. What is the longitude of NYC? (Local Time in NYC is

earlier than Greenwich)

Step 1: What is the time difference? _______

Step 2: Multiply difference by 15⁰: _______

Step 3: West or East? _________

Answer: __________

5 hrs

5 x 15 = 75o

West

75o W

A tougher example:2. It is 12 noon at the Prime Meridian. You are on

a boat where it is 4:00 am. You look up at the sky and determine the altitude of Polaris to be 35°. What is your latitude and longitude?

Latitude: ALtitude of Polaris = LAtitude of observer 35oN

Longitude: 8 (time difference) x 15o = 120o W

35oN, 120oW