Maps

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DO Now

• List differences between latitude and longitude
• Why are there time zones on Earth?
• If it 2pm in New York State and California is 45
  degrees west, what time is it in California?

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Mapping the Earth
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Measure the Earth

• Relationship between altitude of Polaris and a
  persons latitude in the Northern Hemisphere
• The true shape of Earth
• Observations of the sky are affected by Earth
  rotations

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Shape of the Earth

• Perfect sphere-
• Polar diameter equals equatorial diameter (PDED)
• Earth has a slight bulge

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Oblate Spheroid

• flattened slightly at the poles and bulging at
  the equator
• Polar Diameter12,715 km
• Equatorial Diameter12,756km
• Therefore ED gt PD

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Proof that Earth is an Oblate Spheroid

• Photographs from space (most direct)
• Altitude of Polaris (north star)
• Polaris is almost located directly over the North
  Pole
• As an observer travels north or south the
  altitude of Polaris changes

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POLARIS (AKA North star)
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More Proof

• 3. Gravitational Measurements
• Differences in weight of an object at the equator
  and the poles
• 4. Early Observations
• As a ship sails away from shore it appears to
  disappear from the bottom up

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Determine Polaris

1. Latitude is equal to the angle of Polaris in the
   Northern Hemisphere

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What is the latitude of the observer?

1. 10 North
2. 20 North
3. 40 North
4. 70 North

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Polaris

• Is always north of the north pole
• It is a celestial object
• It circumvents the Earth

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Maps Projections

• Latitude and Longitude