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Understanding Latitude and Longitude

Understanding Latitude and Longitude

The map grid system of coordinates, latitude and longitude, can pinpoint any location on earth. The system was developed back in the middle ages and is still in use today. When looking at a map, latitude lines (also referred to as parallels) run parallel to the equator while longitude lines (also referred to as meridians) run perpendicular. If you find yourself forgetting which is which, think of latitude as the rungs of a ladder (“ladder-tude”). To precisely locate points on the earth’s surface, latitude and longitude are divided into degrees (°). Degrees are further divided into minutes (‘) and seconds (“). There are 60 minutes in each degree; 60 seconds in each minute, and seconds can be further divided into tenths, hundredths, or even thousandths

The equator is located exactly halfway between the north and south poles, dividing the earth into the northern and southern hemispheres, and thus is the baseline for latitude, denoted as 0° Latitude. Latitudes are imaginary lines that circle the earth horizontally and are stacked on top of one another, each one having a smaller diameter until finally reaching the north and south poles at 90°N and 90°S. Latitudes north of the equator are also written as positive values, while latitudes south of the equator are written as negative values (North Pole = 90°; South Pole = -90°).

The baseline for longitude is located along the prime meridian, an imaginary line that runs atop the British Royal Observatory in Greenwich, England from the North Pole to the South Pole, and is denoted as 0° Longitude. Unlike latitude, longitude lines are only half circles, running vertically between the two poles, each being equal in length. Longitudes east of the prime meridian are written as 0 to 180°E or as positive values, while latitudes west of the prime meridian are written as 0 to 180°W or as negative values.

So why then are the degrees further divided into minutes and seconds, besides providing the ability to precisely pinpoint a location? Well, longitude is also an important tool in measuring time. The earth makes one complete rotation on its axis approximately every 24 hours. The earth turns about 15° of longitude, or 1/24th of 360°, every hour. The world’s time zones are generally divided into 15° of longitude and the time in each zone is based on its distance from the prime meridian.