Latitude and longitude comprises a grid system of lines encircling the globe and are used to determine the locations of points on the earth. Lines of latitude, also called parallels, run east - west. Latitude lines always run parallel to each other, and hence, they are always an equal distance apart. Latitude lines never converge or cross. The equator is referred to as 0o latitude, and the North and South Poles are located at 90o north and 90o south latitude respectively. In other words, values for latitude range from a minimum of 0o to a maximum of 90o.
Lines
of latitude measure distance north or south of the equator. The
latitude of a particular location is the distance, measured in degrees,
between that place and the equator. This distance is measured along a
meridian, or line of longitude. If the earth were a perfect sphere
(which it isn’t), the distance, or the length, of 1o of latitude would be constant everywhere. In reality, the earth is slightly flattened at the poles, so the length of 1o of latitude at the poles is slightly more than at the equator. At the equator, the length of 1o of latitude is equal to 110.6 km (68.7 mi.) and at the poles, the length of 1o of latitude is equal to 111.7 km (69.4 mi.). For our purposes, we will assume the length of one degree of latitude is 111 km.
Lines of longitude, also called meridians, run north - south. Meridians are farthest apart at the equator, and converge at the North and South Poles. The prime meridian, which runs through Greenwich, England, is referred to as 0o
longitude. Points are measured east or west of the prime meridian until
one reaches the opposite side of the prime meridian, which is referred
to as the International Date Line. This is considered 180o longitude, and is the highest value which longitude can take. In other words, values for longitude range from a minimum of 0o to a maximum of 180ofor more Link : http://www.digitalmobilemap.com/latitude-and-longitude-getting-started
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