# Maps and models of the earth

### 12 terms by CherieVeit

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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

Example: