Latitude and Longitude

A globe has two fixed points—the North Pole and the South Pole. An imaginary line equator is drawn in such a way  that at all points it lies exactly halfway between the two poles. It divides the earth into two equal parts i.e., the Northern Hemisphere and the Southern Hemisphere. One set of lines drawn in between the two poles in an east-west direction are called parallels of latitudes. The other set of lines drawn joining the north and the south poles are called meridians of longitude. The equator has a latitude of 0°. The distance between any two parallels of latitude is always equal.

Important Parallels of Latitude

1. The Tropic of Cancer : It is in the northern hemisphere at an angular distance of 23l/2° (23°30’N) from the equator.

2. The Tropic of Capricorn : It is in the southern hemisphere at an angular distance of 23l/2° (23°30’S) from the equator.

3. The Arctic Circle : It lies at a distance of 66l/2° (66°30’N) north of the equator.

4. The Antarctic Circle : It lies at a distance of 66l/2° (66°30’S) south of the equator. There are two solstices each year, called the Summer Solstice and the Winter Solstice.

Summer Solstice : The day of 21st June when the sun is vertically overhead at the Tropic of Cancer (23°30’N).

Winter Solstice : The day of 22nd December when the sun is vertically overhead at the Tropic of Capricorn (23°30’S).

Meridians of Longitude

The semi-circles running from pole to pole or from north to south are known as meridians of longitude and distance between
them is measured in degrees of longitude. Greenwich Meridian or Prime Meridian with a value of 0° longitude serves as a
common base for numbering meridians of longitude lying on either side of it — east as well as west. There are 360 meridians
including Prime Meridian. Each degree of a longitude is divided into sixty equal parts, each part is called a minute. Each minute
is again divided into sixty equal parts, each part being called a second.

Local Time : Local time of any place is 12 noon when the sun is exactly overhead. It will vary from the Greenwich time at the rate of four minutes for each degree of longitude.

Standard Time : It is the uniform time fixed by each country. It is fixed in relation to mean time of a certain meridian which generally passes through it.

Greenwich Mean Time : The time at 0° longitude is called Greenwich Mean Time. It is based on local time of the meridian passing through Greenwich near London.

Indian Standard Time : It is fixed on the mean of 821/2°E Meridian, a place near Allahabad. It is 51/2hours ahead of Greenwich Mean Time.

International Date Line : It roughly corresponds to 180°E or W Meridian of longitude and the date changes by one day as this line is crossed. If one crosses this line from east to west a day is added, and a day is subtracted while moving from west to east.