How to Read GPS Coordinates

This is perhaps one of the most common questions asked by all GPS owners. Without a doubt, many people find it difficult to read and understand GPS coordinates. This is not surprising because GPS coordinates come in many forms and formats.

Some use notations represented as pure decimal numbers while others are using notations such as minutes, seconds and degrees. The main purpose of a GPS device is to allow you to mark and determine the location of a particular place or waypoint. Hence, understanding the symbols and meaning of the coordinate is important in fully enjoying the navigation utilities of this device.

First, let's talk about formats. Let us review some of the salient points of your geography class. The earth is divided by the equator into hemispheres; the northern hemisphere and the southern hemisphere. Also, the world is divided into west and eastern regions by the prime meridian. These imaginary lines are used by the GPS to give the coordinates of a location.

Some GPS devices would give you coordinates in this format: N 25° 07.450', which refers to a location that is more than 25 degrees north of the equator. With coordinates like S 25° 07.450', this refers to a location that is a little more than 25 degrees south. The same trick applies to the values of west (W) and east (E) portion of the prime meridian.

GPS coordinates use latitude and longitude, which are often recorded as degrees, minutes and seconds. 60 degrees equate to 1 minute and 60 minutes equate to one degree. By general standards, 1 degree latitude equals 69 miles, 1 degree longitude equals 42 miles. 1 minute latitude is equivalent to 6072 feet and 1 minute longitude equates to 3696 feet. 1 second equates to 101.2 feet, 1 second longitude equals 61.6 feet.

Here is a sample conversion from degrees, minutes, seconds to decimal degrees:

• In a given coordinate of 118 degrees 8 minutes 26.2353 seconds West, let's do a conversion from degrees, minutes and seconds to decimal degrees.
• 118 degrees 8 minutes 26.2353 seconds West = -118.1406209154
• 118 + 8/60 + 26.2353/3600 = 118.1406209154
• Units are negated to indicate direction (West latitude or South longitude)

To give another coordinate format, consider 25.124167 as a given coordinate, which basically is just degrees, a pure decimal number. Again, don't ignore the fraction.

• Take it and multiply it by the number of minutes in a degree (0.124167x60=7.450 minutes). This gives you a coordinate of 25 degrees and 7.450 minutes.

• With actual numbers, a given latitude of N 25 07.450 is the same as N 25° 07' 27", or simply 25.124167. If you are calculating distances using coordinates, never ignore the decimal points as they represent a fraction of minutes. Observe:
• N 25 07.450 is the same as 25 degrees and 7.450 minutes North of the Equator
• To calculate for the fraction portion of the minutes, multiply the decimal portion to the number of seconds in a minute (.450 x 60 = 27). Hence, 7.450 minutes is equivalent this coordinate: 7 minutes and 27 seconds (7' 27").

Now, refer to your map, find the location indicated by the given coordinates. Use the degrees-minutes-seconds format and find out where they intersect to establish GPS location. Some GPS devices have conversion features to make it easier for you to spot map locations.

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