Longitudes extent from the north pole to south pole. These are the north-south lines. All meridians are halves of great circles.
Latitudes are the east-west lines. Only one latitude, the equator, is a great circle.
Relative location : It tells a particular place with respect to another place.
Absolute location : It indicates position based on the coordinates of a grid system.
Temperature and Time : Latitude tells of temperature differences on the earths surface. The latitude gives a good idea about the climate and vegetation. Longitude causes time to differ at different places on earth.
Angular distance : In this case, the distance is measured and expressed in degrees.
Latitude
1. It is the angular distance of a place north or south of the equator.
2. There are 180 parallel lines of latitude.
3. Each parallel of latitude is a circle.
4. All parallels of latitude are not equal. The circles become smaller towards the pole. At equator the circle is largest.
5. The distance between any two latitude is always equal.
6. The North Pole and the South Pole are fixed points and serve as basic points of reference.
Zenith distance : It is the angle which the Sun makes at noon with the zenith.
Declination of the Sun : The angle which the Sun makes north or south of the Equator on a particular day is called declination of the Sun. This information can be obtained from the Nautical Almanac which gives the declination from day to day.
Latitude and Heat Zones of the Earth
The Earth gets heated differently on the surface because of its spherical shape. The region near the Equator gets more heat in the form of direct rays from the Sun. These rays are concentrated over a smaller area and so it heats up the Earth more.
As we go down the Equator, due to the curvature of the Earth, the Sun’s rays strike the Earth’s surface at an angle. Hence the temperature decreases as we go down the Equator.
Torrid Zone : The area between the Tropic of Cancer and Tropic of Capricorn receives direct rays of the Sun almost throughout the whole year. This region receives more heat and is called the Torrid (hot) Zone.
Temperate Zone : The areas between the Tropic of Cancer and Arctic Circle in the Northern Hemisphere and the Tropic of Capricorn and Antarctic Circle in the Southern Hemisphere are less hot because the angle of the Sun’s rays goes on changing towards the poles. These regions get moderate heat and are therefore called the Temperate Zones.
Frigid Zone : Near the polar areas, the sun rays are very slanted and therefore it is very cold.
The areas between the Arctic Circle and the North Pole in the Northern Hemisphere is very cold and is called the Frigid Zone.
There is a similar area in the Southern Hemisphere between the Antarctic Circle and the South Pole which is also called the Frigid Zone.
Latitude and Temperature : Latitude is concerned with the tempe-rature and tells us about the climate and also the related vegetation and animal life.
Longitudes and Time Zones
Longitude
1. It is the angular distance of a place east or west of the Prime Meridian.
2. There are 360 meridians of longitude.
3. The Prime Meridian is a longitude of 0O.
4. Each meridian of longtitude is a semi-circle.
5. All meridians are of equal length.
6. The distance between any two meridians is not equal. They converge from the Equator to the Poles.
Longitude and Time
Longitude and time are related with each other. As the Earth rotates, every place has its sunrise, sunset and noon.
When the sun is at its highest point in the sky, it is noon or it is called zenith.
Local time : The local time is the time of a place at the mid-day sun.
The Earth takes 24 hours to complete one rotation and the places in the east see the sun first. Places in the west see the sun later.
Therefore,
1. For each 1O of longitude towards the east, a time of four minutes has to be added.
2. For each 1O of longitude towards the west, a time of four minutes has to be subtracted.
Standard Time : When the local time of a central place is taken as the time for the whole country, it is called the Standard Time of that country.
Indian Standard Time : In India, the longitude of 82.5OE, passing through Allahabad is considered as the Standard Meridian. When it is noon on this longitude, the time is taken as noon for the whole country.
This is known as the Indian Standard Time (IST).
Time zones : A time zone is an area in the world where clocks record the same time.
In 1884 a group of countries established standard time zones for the whole world.
Each zone is almost 15O wide, with adjustment made in some places so that a city or country is not divided into two time zones. A separation of one time zone indicates a difference of one hour between two places.
Clocks to the east of a time zone are set for one hour later while; clocks to the west, one set one hour earlier.
Greenwich Mean Time (GMT) : For international uniform time, corresponding to the Prime Meridian, which is adopted by all countries. This is called the Greenwich Mean Time or G.M.T.
International Date Line
International date line is one at which a day is lost or gained.
1. East of Greenwich : When you go eastwards from Greenwich to a place A on longitude 180O, the time will be 12 hours ahead of Greenwich time.
2. West of Greenwich : When you move westward from Greenwich to the same place A on longitude 180O, the time will be 12 hours behind Greenwich time.
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