How to Locate Longitude

Imaginary lines of longitude and latitude crisscross the globe making it possible to pinpoint any location on Earth.

Meridians are imaginary lines across the Earth that run from the North Pole to the South Pole and are used to help pinpoint a particular location. Meridians measure longitude and are often referred to as lines of longitude. Longitude is the degrees east (E) or west (W) of the Prime Meridian, the starting point for the meridian lines. When measuring longitude, the letters E or W follow the degree symbol. The Prime Meridian, which crosses through Greenwich, England, is at 0 degrees longitude. On the exact opposite side of the world is the International Date Line, which is at 180 degrees. It is neither east nor west of the Prime Meridian. Lines that go left on the map from the Prime Meridian to the International Date Line are measured in degrees west, while lines that go right are measured in degrees east.

Instructions

1. Put your finger on the spot on the map for which you want to find longitude.

2. Locate the nearest vertical line of longitude. Follow that line up or down on the map with your other finger until you reach the degree measurement, such as 30 degrees E.

3. Look at the nearest longitude line on the opposite side of your finger. Determine how many degrees are between the two lines. For instance, on world maps there are usually 10 degrees between each line shown.

4. Determine the approximate longitude of your spot on the map by figuring out about how far the line of longitude is from your location. For example, if the location is about halfway between 70 degrees W and 80 degrees W, then the longitude is approximately 75 degrees W. Maps of local areas can give more precise measurements than a map of an entire country or the world.

References

• "Geography: The World And Its People"; Richard Boehm et al.; 2002