Making Sense of a GPS Coordinate



A GPS coordinate system expresses all locations on earth using two of three coordinates found in a spherical coordinate system that's aligned with the spin axis of the earth. The simplest way to represent a point on a two-dimensional map is by using two lines that cross. One line goes up and down while another goes from side to side. Where they converge is now the point you're interested in. It could be a waterfall, a campsite or lake or wherever you're standing at any given point in time. People working with maps refer to such lines as global positioning system coordinate lines. These GPS coordinates are usually given as a set of numbers for one line and another set for another line. Positioning the two lines on a map equals a point.

GPS Coordinate 101

The earth is shaped like a sphere so any errors don't matter much. GPS coordinates can be used on spherical earth but it's a bit more difficult. This explains why there are different GPS coordinates systems that have been developed to pinpoint various locations on maps. GPS coordinates systems that show the standard degrees-minutes-seconds coordinates are considered the most popular. There are a total of 360 degrees but you can only go as far as 90 degrees north or south latitude. You can only reach just shy of the 180-degree mark east or west longitude. At the area of the equator, longitude degree stretches to over 69 miles wide, necessitating smaller divisions for accurate depiction of points.


This GPS coordinates system is like a clock. Think of each degree as equivalent to one hour. Degrees are broken up into 60 minutes and minutes into 60 seconds. One minute is still over one mile wide at the equator. A second at 0.0192 miles is a bit more manageable, but still above 100 feet. The longitude lines draw closer together till they reach the poles. Latitude lines on the other hand, remain at the same distance from each other all the way to the poles. Distances between latitude lines are easier to figure out as they're always the same figures given for the equator longitude numbers. To maintain accuracy, a degree=69.1722 miles, a minute=1.1528 miles and a second=101.45 feet.

Another system is the decimal form. This system is also frequently used for global positioning system receiver manufacturers for handling data within their GPS units. Whenever people wish to see a different GPS coordinates format, everything gets converted from decimal data in machines to one's requested GPS coordinates system and displayed on the global positioning system screen. In this system, the seconds appear absent. They are there, only they're indicated as decimal fractions of minutes.