How are the latitude and longitude of a given place on earth determined?

Latitude and longitude, the basic tools of map making, are imaginary lines traced on the surface of the earth for the purpose of locating a specific place. 

The lines of latitude run east and west, and are parallel to each other. For convenience, the earth has been divided into 360 degrees of latitude. Measure of latitude starts at the equator and is measured as 90 degrees north to the North Pole and 90 degrees south to the South Pole. Each degree represents 60 nautical miles on the earth's surface. 

The lines of longitude run north and south and are not parallel to each other. Consecutive degrees of longitude are 60 miles apart at the equator, and all come together at the North Pole and the South Pole.These are 360 degrees of longitude _ 180 degrees lie east, and 180 degrees lie west of Greenwich, England, an arbitrary starting point used by all mapmakers.

Latitude is the measure of how far north or south a location is from the equator. 1 degree of latitude is equivalent to about 111 km and one minute is about 1.85 km. The latitude of an area is one factor in the kind of climate the area might have. If an area is located close to the equator, the climate will be very hot, or tropical.

Longitude is a measure of how far east or west a place is from the Prime Meridian. The longitude lines or meridians as they are sometimes called are imaginary lines every 20 degrees east or west of the Prime Meridian.While  

the latitude of a particular location affects its climate, the longitude can determine the time zone a particular location is in.When latitude and longitude lines are overlaid on each other on surface of earth , they form a grid. If you know the latitude and longitude of a place, it is possible to locate that place and vice versa, on a globe or map.Today, with the aid of satellites, Global positioning systems (GPS) uses the spherical trigonometry.Someone with the proper instruments(GPS receivers ) on even a small yacht can measure latitude and longitude of any place within an accuracy of 30 cm.

Source: The Hindu