Mapping Hacks

Work with Multiple Lat/Long Formats #25

Chapter 3, Mapping Your World

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HACK

equator. Lines of longitude are referred to as meridians and extend 180

degrees west and east of the prime meridian, which passes through the site of

the Royal Observatory in Greenwich, England. Southern latitudes and west-

ern longitudes are often represented as negative numbers. Minutes are

shown with a single quote ('), and seconds are signified with a double quote

(").

In traditional notation, one particular spot in the O’Reilly parking lot is at

38° 24' 57.636" north latitude, 122° 50' 27.348" west longitude.

Each minute of change in latitude or longitude at the equa-

tor equals one nautical mile, or 6,076 feet. So one second of

latitude or longitude is approximately 100 feet. This means

that 57.636 seconds of North latitude implies a precision of

about an inch, which is well beyond the precision of the GPS

used to take this reading.

A Couple of Easy Ways to Convert

If you are working with your own waypoints, you can avoid conversion alto-

gether. Set your GPS to display coordinates in the format that matches your

map. On some Garmin units, for example, this is found under Menu

➝

Setup ➝ Position ➝ Position Format.

The easiest way to handle conversions is to let an online coordinate con-

verter do the work. The Federal Communications Commission (FCC) runs

one such site at http://www.fcc.gov/mb/audio/bickel/DDDMMSS-decimal.html ...