I.
TOPIC 6
Earth Coordinate System
1. Great Circle
2. Small Circle
3. Meridian
4. Prime meridian
5. Equator
6. Latitude
7. Longitude
8. Parallel of Latitude
II. LEARNING OUTCOMES
At the end of the session, students must be able to:
Explain the significance of earth coordinate system to navigation
Introduction: This topic introduces the terms used in coordinate system.
III. INSTRUCTION/LEARNING ACTIVITY
1.
Great Circle
Great Circle - A Great Circle is any circle that circumnavigates the Earth and passes through the
center of the Earth. A great circle always divides the Earth in half, thus the Equator is a great circle
(but no other latitudes) and all lines of longitude are great circles.
2.
Small Circle
Small Circle- The poles are an imaginary line running from the axis of Earth's rotation. Small circles
are circles that cut the earth, but not into equal halves. Examples of small circles include all lines of
latitude except the equator
A Great Circle is a plane that passes through the center of the earth. (e.g. Equator and all
Meridians). The shortest distance between any two points on the earth's surface is attained along
the arc of a Great Circle. Small Circles are lines that do not pass through the center of the earth.
2.
Meridian
a circle of constant longitude passing through a given place on the earth's surface and the terrestrial
poles
one of the imaginary lines that goes around the Earth from the North Pole to the South Pole. These
are used for measuring position, time etc.
3.
Prime meridian
The prime meridian is the line of 0° longitude, the starting point for measuring distance both east
and west around the Earth. The prime meridian is arbitrary, meaning it could be chosen to be
anywhere
4.
Equator
an imaginary line drawn around the earth equally distant from both poles, dividing the earth into
northern and southern hemispheres and constituting the parallel of latitude 0°
5.
Latitude
the angular distance of a place north or south of the earth's equator, or of a celestial object north or
south of the celestial equator, usually expressed in degrees and minutes.
"at a latitude of 51° N"
6.
Longitude
Longitude is the measurement east or west of the prime meridian. Longitude is measured by
imaginary lines that run around the Earth vertically (up and down) and meet at the North and South
Poles. These lines are known as meridians. ... The distance around the Earth measures 360
degrees
7.
Parallel of Latitude
The parallel of latitude is an imaginary line around the Earth that is parallel to the equator. An
example of a parallel of latitude is the Arctic Circle that runs east - west around the Earth at a
latitude of 66° 33' 44"