Latitudes, Longitudes and Time
The shape of the earth resembles an oblate spheroid. It is difficult to position its surface features as there is no point of reference to measure relative position of the other points. A network of imaginary lines is drawn to locate various places.
Imaginary lines running vertically on the earth are called meridians of longitude. Imaginary lines running horizontally on the earth are called parallels of latitude.
The latitudes and longitudes together make the grid system of the earth. This network of intersecting lines is used to fix the location of different features.
Latitudes and longitudes are measured in degrees as they represent angular distances. Each degree is divided into 60 minutes. Further, each minute is divided into 60 seconds.
Latitude is the distance from the Equator along the Y axis in both, North and South.
The extent of the part of the earth is expressed by the latitudes in the relation to the north or south of the Equator.
Longitude is the distance from the Prime Meridian along the X axis in both, the East and the West.
The meridian of longitude passing through the Greenwich observatory has been adopted as the Prime Meridian.
Difference of 1° longitude leads to a difference of 4 minutes. Thus, every 15° results in plus minus one hour.
Time zones are broad strips that measure 15 degrees wide. Time zones differ from their neighbouring time zones by 1 hour. The world is divided into 24 major time zones.
In order to maintain uniformity of time within the territorial limits, every country has selected its own standard time. Standard Meridian is the central meridian of the country. Indian Standard Meridian is chosen as 82°30’ East.
Indian Standard Time is ahead of the Greenwich Mean Time by 5 hours and 30 minutes.
International Date Line is an imaginary line that separates two consecutive calendar days. It coincides with the longitude of 180°. It has zigzagged at seven places to avoid splitting apart countries into two days.