The decimal system is easy to calculate with a standard electronic calculator. It's similar to the way a dollar bill is divided into tenths (dimes) and hundredths (pennies). The easiest system to understand is the decimal method in which each degree is divided into tenths, hundredths, thousandths, and so on. Two systems are commonly used to express a part, or fraction, of a degree. Notice that while longitude runs from 0 to 180° east or west, latitude lines run only from 0 to 90° north or south. This is the approximate location of the International Dateline. (The prime meridian was established in 1884 by the International Meridian Conference held in Washington, DC.) Longitude lines are positioned in degrees east and west of the prime meridian to the 180° point on the opposite side of the globe. They are similarly expressed in degrees relative to the famous reference prime meridian (0°) running through the Royal Observatory in Greenwich,Įngland.

Notice that they run from pole to pole perpendicular to the latitude lines. Longitude lines, sometimes called meridians, are shown in Figure 2. The north pole is +90° and the south pole is -90°. The Equator is defined as 0' latitude and each pole is at 90' latitude. They are defined by their position north or south of the Equator in degrees.

The latitude lines, sometimes called parallels, are the ones that run parallel to the Equator. Can you refresh my memory?Ī: Certainly - but first take a look at Figure 1. My apologies to Mr Conlin, an excellent teacher, but it really has been a few years for me. Q: I seem to recall this from my fifth-grade geography class. Any point on the globe can be defined by the intersection of two ordinate lines. These lines divide our entire planet into a system of coordinates. If not, just about any map will do.Īs you look at your globe or map, notice the lines that run north to south as well as east to west. How do I determine my own grid square?Ī: Before we get into grid squares, let's take a quick look at one of the more common methods used to define locations. They say that grid squares are usually exchanged during these contests, but I'm not sure what a grid square is. Q: I'm interested in trying my luck in an upcoming ARRL VHF/UHF or 10-GHz contest because I'm gunning for my VHF/ UHF Century Club award. Mike Gruber, WAISVF, ARRL Laboratory Engineer, walks you through this maze and helps you discover where you are - geographically, if not metaphysically! -WB8IMY An alternative title for this month's column might be: Everything You've Always Wanted to Know About Coordinates and Grid Squares But Were Afraid to Ask.Īs more hams explore the worlds of VHF, UHF, microwave and satellite operating, we receive an increasing number of questions about grid squares in particular and geographical coordinates in general.

Ham radio grid map