LESSON NOTE ON MAP

WHAT IS A MAP?

Introduction

1. Even from the earliest days the urge for man to explore has been great. The early travellers used natural features to help them find their way from place to place.

By noting the position of the stars, the moon and the sun, man devised a method of finding out where he was. This meant exploration past known boundaries was now possible. As the explorer ventured further and further from home and recognizable features disappeared, he would often sketch his surroundings so that the way home could be found more easily. These early ‘maps’ where often drawn on animal hide, stone or reed paper.

2. If we think of the earth as a sphere, we can imagine how it could be covered with imaginary lines to help pinpoint a position on the surface. First of all the earth has an axis, running from the True North pole to the True South pole - the only 2 points on earth that do not rotate. Next, imagine a line that runs around the middle of the earth half way between the North and South poles- this circular line is called the equator.

3. If we add more lines running parallel to the equator, they will also be circular, though smaller than the equator; they are called lines of latitude. Lines on the Earth’s surface drawn from pole to pole are called lines of longitude.

Longitude

4. Longitude lines, also called meridians, are circular. They are numbered and have a starting point at Greenwich in England. This line is numbered zero and called the prime meridian- all other lines are either east or west of it. Every meridian from one pole to the other - is a semi-circle, and has an anti-meridian on the opposite side of the earth. A meridian and its anti-meridian together make a full circle round the earth.

5. By numbering the lines, it means that the whole of the earth can be covered.

The position of each line is expressed in degrees away from the prime meridian.

For example in the diagram point ‘A’ is about 20° (degrees) west of the prime meridian. Point ‘B’ is about 40° east of the prime meridian. Although this system can give reasonably accurate positioning it is not accurate enough for everyday use, so each degree is further broken down into 60 minutes. This now gives us a system of describing a point’s location in terms of degrees and minutes either east or west of the prime meridian (Greenwich).

Latitude

Lines of Latitude

6. Lines of latitude are circles drawn around the earth, parallel to the equator.

The equator, at zero degrees, splits the earth into two halves, the northern hemisphere and southern hemisphere. Using the lines of latitude you can describe any point’s location in degrees and minutes either north or south of the equator.