# Longitude and Latitude

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Longitude and Latitude
Earth 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 NW NE W E SE SW S

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 Tropic of Cancer 23.5° N. Equator
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.

Example 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 75° West Longitude West 75o W

A tougher example: 35oN, 120oW
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 35° N; 120 ° W 35oN, 120oW