GEOG 181 Week 3

What is the shape of the Earth?

Oblate spheroid

What shape can we use to represent Earth?

Ellipsoid

Why are there different types of ellipsoids to model the Earth?

Different ellipsoids were developed to fit different regions of the Earth

WGS 1984 ellipsoid

Developed for the global GPS system

What can we use to represent the lumpy surface of the Earth?

Geoid

Latitude

Measures our position north or south of the equator

Lines of latitude are called

Parallels of latitude

Average length of a degree of latitude

111km

Parallels of longitude run in what direction?

East and west, measuring 90° north or south of the equator

Longitude

Measures our position east or west of the prime meridian

Where is the prime meridian located?

Greenwich, England

Lines of longitude are called?

Meridians

Are lines of longitude parallel?

No, they converge at the poles

The length of one degree of longitude at the equator

111km

Length of one degree of longitude at a particular latitude

Length of 1º longitude = 111 km * cosine (latitude)

Great circles

Created by intersecting a plane with the centre of the Earth

Small circles

Created by intersecting a plane with Earth, not going through the origin

Loxodromes

A line of constant bearing or compass direction

The meridians of longitude represent how much of a great circle route?

Half

Datum

A mesh of reference points which translate positions indicated on maps to their real position on the surface of the Earth