# Maps

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## Maps

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##### Presentation Transcript

1. Maps • a model or representation of the Earth’s surface

2. Eratosthenes • Greek mathematician who calculated the Earth’s circumference in ~240 BC • using geometry and observation, his observations made more than 2,000 years ago were off by 6250 km => only 15%!

3. Finding direction on the Earth

4. Reference point • a fixed place on the Earth’s surface from which direction and location can be described

5. Axis • an imaginary line through the earth about which the planet rotates

6. North Pole • north end of the axis

7. South Pole • south end of the axis

8. Cardinal directions • north, south, east, west and various combinations of these directions

9. “North on top” • is arbitrary • Europeans – placed east on “top” to show the importance of Jerusalem to their faith • Chinese – placed south on “top” as nothing of interest to them was to the north

10. Compass • uses the natural magnetism of the Earth to indicate direction • compass needle points to the magnetic north pole • the Earth has 2 different sets of poles => geographic poles and magnetic poles • magnetic poles have a slightly different location than the geographic poles

11. Chinese Compass 220 BCE

12. True North and Magnetic Declination

13. True North • geographic North Pole • never changes position • the difference between magnetic north and true north (geographic north pole) requires a calculation

14. Magnetic Declination • is measured in degrees east or west of true north • has been determined for different points on the earth’s surface • when the declination of an area is known, a compass can be used to determine true north

15. Finding locations on the Earth

16. Latitude (parallels) • imaginary lines drawn around the earth parallel to the equator • definition – the distance north or south, measured in degrees, from the equator • North Pole 90 degrees N 90°N • South Pole 90 degrees S 90°S

17. Equator • an imaginary line half way between the poles that divides the earth into the Northern Hemisphere and the Southern Hemisphere

18. Longitude (meridians) • imaginary lines that pass through the poles • are not parallel • definition – is the distance east or west, measured in degrees, from the Prime Meridian