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12 terms

Maps and models of the earth

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2000 years ago, the Greeks thought that the Earth was a perfect sphere - Earth actually bulges out around the
equator and is slightly squashed at the poles
Erotsthenes
Greek mathematician, calculated the Earth's circumference using geometry and observation of the sun - his estimation was off only 6,250 km, an error of 15%
Reference point
A fixed place on the Earth's surface from which direction & location can be described
North and South Poles
used as refence points when describing direction and location on Earth
Equator
also used as a refernce point when describing location on earth - a circle halfway between the poles that divides the Earth into the Northern and Southern Hemispheres
Cardinal directions
North, South, East, & West
Magnetic Compass
One way to determine North which uses the natural magnetism of the Earth to indicat direction
Magnetic North Pole
Where the compass needle points to
Geographic poles and Magnetic poles (have changed location throughout history)
The Earth has two different sets of poles
Geographic North Pole
never changes and is called true north
Difference between geographic north and magnetic north
When using a compass to map or explore the Earth's surface, you need to make correction for the
Magnetic declination (magnetic declination is different for different points on the Earth's surface
the angle of correction ... and is measured in degrees east or west of true north