The latitudes and Longitudes are imaginary lines sketched over the globe (the spherical form of the earth’s dummy) to pin point of the exact location on the earth. These are the virtual lines, draw over the surface of globe at an equal difference on both directions – horizontally and vertically. Horizontally lines are called Latitudes while vertical lines are called Longitude or median lines.
To know more, let’s elaborate it. Imagine our earth is in the sphere size (however, the original size of the earth is slightly different and earth is an irregular shape approximating a biaxial ellipsoid). To divide this sphere into four pieces, we draw two imaginary lines on it – one horizontally around the globe from the mid point to the mid mid point and another vertical imaginary line from mid point to mid point around the globe. Practically, the mid point of the earth is considered at the South Atlantic Ocean. The horizontal mid line is known as Equator while vertical midline is known as Prime Median line.
The north and south tip of the earth are known as North Pole and South Pole respectively while equator is considered the mid line which bifurcates the earth in North and South. In the similar manner, the Prime Median divides the earth in East or West. The unit of measuring the earth is Degree. The latitude value of Equator is zero degree. The lines are drawn on the earth’s surface in the form of arc.
Latitude Lines:
The latitude lines are drawn on the earth’s surface in horizontal arc on both sides of equator. The earth’s surface is virtually divided by 180 horizontal lines – 90 above the equator and 90 below the equator – sketched on equal differences. The difference between the two lines is approximately 69 mile (111 k.m.), which changes slightly towards poles because the earth’s actual size is not a perfect sphere. Thus the North Pole is valued as 90° N and South Pole is measured as 90° S. When the directional designators are omitted, northern latitudes are given positive values and southern latitudes are given negative values. It is denoted as Greek letter phi (φ).
Longitude Lines:
Longitudinal lines are perpendicular to the latitude lines sketched vertically on the entire earth’s surface. As the earth is not symmetrical, there is no mid longitudinal line on the earth and like latitude lines, longitude lines are not parallel. However, the geographers through the international agreement have given the value of zero to Greenwich, England and it is considered the Prime Meridian line. There are 360 longitudinal lines – 180 lines on the west side and 180 lines on the east side – sketched vertically on the earth’s surface passing through the poles. The difference between each two longitudinal lines is 69 miles (111 k.m.) that slightly varies on the far east and west area of the earth, due to earth’s asymmetrical structure. The measurement of the west direction is measured with W and East zone is measured with E. If the directional designator is omitted these longitudes are given positive values or negative value respectively. It is denoted as Greek letter Lamda (λ).
