It is difficult to describe the location of a point on a sphere, so is for the earth. Now the question arises as to how to locate a place on it? We need certain points of reference and lines to find out the location of places.These points are located with Longitude and Latitude. So now let’s see the difference between Latitude and Longitude.
It is basically defined as the angular distance of the places in North and South direction of Earth equator.
The equator is an imaginary circular line and is a very important reference point to locate places on the earth. All parallel circles from the equator up to the poles are called parallels
of latitudes. Latitudes are measured in degrees.
The equator represents the zero degrees latitude. Since the distance from the
equator to either of the poles is one-fourth of a circle round the earth, it will measure
¼th of 360 degrees, i.e. 90°. Thus, 90 degrees north latitude marks the North
Pole and 90 degrees south latitude mark the South Pole.
IMPORTANT PARALLELS OF LATITUDES
(i) Tropic of Cancer (23½° N) in the Northern Hemisphere.
(ii) Tropic of Capricorn (23½° S) in the Southern Hemisphere.
(iii) Arctic Circle at 66½° north of the equator.
(iv) Antarctic Circle at 66½° south of the equator.
Longitude is basically a geographic coordinate that is used to measure east and west direction across the globe or earth. It is basically an angular measurement in degree across an imaginary line PRIME MERIDIAN(which is zero degree).
The count should begin from the meridian(imaginary line) which passed through Greenwich, the place where the British Royal Observatory is located. This meridian is called the Prime Meridian. Its value is 0° longitude and from it we count 180° eastward as well as 180° westward. The Prime Meridian divides the earth into two equal halves, the Eastern Hemisphere and the Western Hemisphere. Therefore, the longitude of a place is followed by the letter E for the east and W for the west. It is, however, interesting to note that 180° East and 180° West meridians are on the same line.
LONGITUDE AND TIME
The best means of measuring time is by the movement of the earth, the moon and the planets. The sun regularly rises and sets every day, and naturally, it is
the best time-keeper throughout the world. Local time can be reckoned by the shadow cast by the sun, which is the shortest at noon and longest at sunrise and sunset. When the Prime Meridian of Greenwich has the sun at the highest point in the sky, all the places along this meridian will have mid-day or noon. As the earth rotates from west to east, those places east of Greenwich will be ahead of Greenwich time and those to the west will be behind it.
The rate of difference can be calculated as follows. The earth rotates 360° in about 24 hours, which means 15° an hour or 1° in four minutes.Thus, when it is 12 noon at Greenwich, the time at 15° east of Greenwich will be 15 × 4 = 60 minutes, i.e., 1 hour ahead of Greenwich time, which means 1 p.m. But at 15° west of Greenwich, the time will be behind Greenwich time by one hour, i.e., it will be 11.00 a.m. Similarly, at 180°, it will be midnight when it is 12 noon at Greenwich. At any place a watch can be adjusted to read 12 o’clock when the sun is at the highest point in the sky, i.e., when it is mid-day. The time shown by such a watch will give the local time for that place. You can see that all the places on a given meridian of longitude have the same local time.