(a) Distinguish between
(i) Latitude and Longitude
(ii) Standard Time and Greenwich Mean Time
(b) If the Greenwich Mean Time is 10:00am, 5th July when Local Time in a place X is 4:48am, 4th July, find the longitude of place X.
(a)(i) Latitude is the angular distance of a point on the Earth's surface, measured in degrees from the centre of the earth. Lines of Latitude run from West to East and they can be used to calculate distance between one place to another. It extends between 90°N and 90°S. Longitudes are imaginery lines running from the North to the South at right angle to the parallel. The longitude that passes through the centre of the earth is called the prime or Greenwich Meridian. Longitude can be used to calculate local time and it extends between 180°W and 180°E.
(ii) Standard Time; is the time generally adopted by a particular country which is usually taken from the central meridian of that country. The need is to eliminate difference in local time between one town and another; otherwise it will result in changing time from one town to another. E.g Nigeria has accepted the meridian of 15°E for her standard time which is 1 hour ahead of the Greenwich Mean Time: Greenwich Mean Time is the time along the prime or Greenwich Meridian which is longitude 0°. It is from the GMT that all countries take their time E.g London and Accra are on longitude 0° and all other countries take their time from the GMT from London. If the GMT in London is 3.00pm, Nigerian time will be 4.00pm.
(ii) Find the time difference
The time difference from 10.00am 5th July to 4.48am 4th July = 29 hours 12 mins.
29 hours 12 mins - 24 hours (one day) = 5hrs 12 minutes
(iii) Convert time difference (5 hrs 12 minutes)to longitude
15° = 1 hour
5 hrs = 15° x 5 =75°
4 minutes = 1°
12 mins. 12 = 3°
4
Total degree = 75° + 3° = 78°
(iv) Since X° is west of 0°, the longitude therefore is 78°W
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