Chapter 3 – Models of the Earth

Section 3.1Finding Locations on Earth

Objectives

Distinguish between latitude and longitude.

Explain how latitude and longitude can be used to locate places on Earth’s surface.

Explain how a magnetic compass can be used to find direction on Earth’s surface.

EARTH REFERENCE POINTS

• AXIS OF ROTATION• NORTH POLE• SOUTH POLE• EQUATOR• NORTHERN

HEMISPHERE• SOUTHERN

HEMISPHERE

LATITUDE

• The angular distance north or south of the equator. This set of circles are called parallels because they run east and west parallel to the equator

DEGREES OF LATITUDE

• Measured and labeled as being north (N) or south (S) of the equator (0°)

• Degree - 111 km (1/360th of Earth’s circumference).

• Maximum values are at the geographic poles (90°N and 90°S).

Minutes and Seconds

• Degrees can be further subdivided:

1° = 60 minutes (60')

1' = 60 seconds (60")

Astrolabe – Early InstrumentUsed To Determine Latitude

LATITUDE IN 1300’S

LONGITUDE• East-west locations

established by using meridians, semi-circles that run from pole to pole.

• Prime Meridian (0°) runs through Greenwich, England.

• Longitude is the angular distance, measured in degrees, east or west of the prime meridian.

Degrees of Longitude

• The meridian opposite the prime meridian is labeled 180°.

• All locations east of the prime meridian have longitudes between 0° and 180°E, those west between 0° and 180°W.

• Can also be subdivided into minutes and seconds.

Distance Between Meridians

• The only place on the earth where 1° of longitude equals 111 km is at the equator. Why?

• All meridians (lines of longitude) meet at the poles, so the distance measured by a degree of longitude decreases as you move from the equator toward the poles.

LATITUDE & LONGITUDE(We Make A Grid To Tell Location)

WHERE ARE WE?(Latitude Comes First, Then

Longitude)• Fall City - 47o33'59"N, 121o54'08"W

• North Bend - 47o29'45"N, 121o47'19"W

• Snoqualmie - 47o31'27"N, 121o49'03"W

Great Circles

• Any circle that divides the globe into halves.

• Often used in navigation, especially by aircraft.

• Shortest distance between any two points on a sphere.

On a map a GC is curved, ona globe it is a straight line.

Finding Direction

• One way is to use a magnetic compass. This is because of the earth’s magnetosphere.

Geomagnetic Poles

• The earth acts like it had a giant bar magnet inside it. It is tilted relative to the geographic poles.

• A compass needle points to the geomagnetic pole.

Magnetic Declination

• The angle between a compass reading and true north, measured in degrees east or west of the direction of the geographic North Pole. A compass reading is only accurate along the line of 0° magnetic declination.

Polar Wander

• The geomagnetic pole, over time, changes position. Today it is slightly west of Ellesmere Island (Canada).

The Global Positioning System (GPS)

• A global network of 24 satellites. Radio signals from 3 satellites allow a GPS receiver to calculate the latitude, longitude, and altitude of the receiver. Accurate to ±15 meters.

ASSIGNMENT

Outlining ReviewSection Outline 3:13.1 Key Terms3:1 Directed Reading

Worksheet