Earth Reference Systems

1. Earth Reference Systems Unit 1, Section 2

2. The Equator • Located half way between North and South Poles • Forms an imaginary, horizontal line that circles the Earth • Hemisphere – one half of the sphere that makes up Earth’s surface • Divides Earth into North and South Hemispheres

4. Tropics of Cancer & Capricorn Tropic of Cancer Tropic of Capricorn 23°S Circle of latitude on the Earth that marks the most southerly position at which the Sun may appear directly overhead Winter Solstice - maximum axial tilt away from the Sun, marking the beginning of Winter • 23°N • Circle of latitude on the Earth that marks the most northerly position at which the Sun may appear directly overhead • Summer Solstice – maximum axial tilt towards the Sun, marking the beginning of Summer

6. Prime Meridian • Imaginary, vertical line • Makes a half circle from the North to the South Pole • Passes through Greenwich, England (0°) • East of Prime Meridian = Eastern Hemisphere • West of Prime Meridian = Western Hemisphere

7. 0° - Greenwich, England

8. Measurement of Sphere • To measure distances around a circle • Units = Degree (°) is (1/360) of the way around the circle • A measure of the angle formed by lines drawn from the center of the Earth to points on its surface

10. Latitude • Distance in degrees North or South of Equator • Horizontal lines • All lines are parallel to equator • Latitude @ equator = 0° • Latitude @ North Pole = 90°N • Latitude @ South Pole = 90°S

11. Longitude • Distance in degrees East or West of Prime Meridian • Vertical Lines • Each longitude line crosses the latitude line, including the equator, at a right angle

13. How was the Reference System Determined? • Polaris – North Star: • Located directly above the North Pole • When the Earth rotates, the North Star remains fixed in the sky • Therefore, it can be used as a point of reference

14. Time Zones • NASA Kids Science News: Time Zones • International Time Zones