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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


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


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

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