Page 40 - Geography for Secondary Schools Student’s Book Form One

Geography for Secondary Schools
Student’s Book Form One

they converge towards the poles. Figure 90°
3.12 shows how the meridians look like.

North Pole
23½°N 23½°N

FOR ONLINE READING ONLY
23½° 23½°

Figure 3.13(a): Determining latitudes

South Pole North Pole
Figure 3.12: Longitudes

Determining latitudes 45°
Latitude is the distance measured in angles
of any point North or South of the equator 45°
at which a perpendicular line is established 0°
from the centre of the Earth towards the
North Pole or the South Pole (90º). Any 45°
angular measurement from the earth’s
centre to its surface represents certain 45°S
latitude (Figures 3.13a and b). The distance
from the North Pole to the South Pole is South Pole
about 20000 kilometres, and there are 180º Figure 3.13(b): Determining latitudes
(half a circle) between them. For example,
the tropic of cancer is drawn on the surface
of the Earth with an angular line of 23½º N Determining longitudes
measured anticlockwise from the equator. A longitude is an imaginary line measured
Latitudes are parallel to each other. They from east or west of the prime meridian.
result into uniform width between them. The angle of longitude is determined by
They have different lengths, decreasing measuring the angle from the centre of
from the equator towards the poles. Equator the earth along the equatorial plane, East
is the longest latitude at the centre of the or West of the prime meridian. Since the
Earth. Therefore, the distance on the earth’s world is about 40000 kilometres round at
surface between one latitude and the other the Equator and there 360º in a circle, the
must be equal to 111 kilometres. distance between each degree of longitude

20000 km at the equator must be:
= 111km
180 o 40000 km
= 111km
1 of latitude = 111km 360 o
o
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