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Coordinate formats (or How do I get from Dº M' S"
to hdddº mm' ss.s'?)

Adapted from GPS Mapping: Make Your Own Maps.

Using degrees, minutes and seconds, the Golden Gate Bridge is located at 37º 49' 10" north and 122º 29' 2" west. You'll sometimes see this format abbreviated as Dº M' S".

To further complicate matters, coordinates can also be expressed as decimals. For example, we could say that the Golden Gate Bridge is located at 37º 49.167'N and 122º 29.033'W. This notation is referred to as decimal minutes, which can be abbreviated as Dº M.M'.

To carry this convention even further, we can use decimal degrees and give the location as 37.81944ºN and 122.48389ºW. This format can be abbreviated as D.Dº.

The above table shows four common ways to abbreviate coordinate formats.

Now for the good news. You should never have to manually convert from one format to the other; your GPS and most software programs will do it for you. If you've been using Dº M' S" and your hiking buddy gives you a coordinate in D.Dº, simply go into the preferences or configuration section of the GPS or software, and change to D.Dº. Once you enter the coordinates, you can change back to Dº M' S". If for any reason you do want to convert coordinates manually, several Web sites offer converters. One is found at http://www.wherearewe.co.nz/dms2dmm.html.

Negative Numbers

Sometimes coordinates are given without cardinal directions (N, S, E, and W), relying
on positive and negative numbers instead. Using this format, anything south of the
equator or west of the prime meridian is negative. For example, our Golden Gate
Bridge coordinates can be expressed as 37.81944º, -122.48389º. Keep this in mind, for
any U.S. location will be west longitude and, if expressed in this manner, must therefore
bear a negative number for longitude.

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