latitude/longitude coordinates for assessing Tropical Storm Gaston rainfall (August 2004)
showing the Eastern Shore of Virginia is more than 75 degrees west of Greenwich, England
Source: NASA
If you're the map reader in the family, you may already remember the basics of latitude and longitude. For the rest of us, remember that latitude measures the distance north or south of the Equator, while longitude measures the distance east or west of a line ("prime meridian") drawn between the North and South poles.
Each degree of latitude north of the Equator is equivalent to 69 miles, so the 36 degree line of latitude is about 2,500 miles (69 x 36 = 2,484) north of the Equator. There are 360 degrees (°) in a circle, and 60 minutes (') in a degree, and 60 seconds (") in a minute.
Latitude is defined in relationship to the poles and the equator. The latitude of the North Pole is 90° north of the equator, while the South Pole is 90° south of the equator. Moving the colonial boundary north half of a degree meant moving it north 30 minutes from 36° to 36° 30' latitude. Longitude, the other line on the map that allows us to define where we are in relation to other places, is the distance from the zero degree meridian. That zero degree "prime meridian" is the line that runs between the North and South poles and crosses through Greenwich, a suburb of London.
The prime meridian could have been defined by any line that connected the poles. Thomas Jefferson tried to establish a prime meridian that ran through Washington DC rather than London. Jefferson was both a scientist and a leader of a revolution against Great Britain's leadership. In the early 1800's, however, England was clearly dominant in science and the English navy ruled the seas. Modern maps with lines of longitude still reflect the primary role that England played in science during previous centuries. In 1884, the International Meridian Conference adopted a common Prime Meridian... but despite this, England still resisted adoption of the metric system for another century.
(There's a online conversion tool that converts between coordinate units.)
Terraserver provides an online tool for finding latitude. If you use it to find a spot several blocks north of where the Virginia Beach Toll Road ends at the Atlantic Ocean, you will be at 36N 51' 43" latitude. That's 36° north of the Equator, plus a few extra miles as indicated by the 51 "minutes" and 43 "seconds" of latitude. In decimal degrees, that location is 36.86198 degrees latitude north of the Equator. Another 8 minutes and 17 seconds of latitude will put you at 37° North, in the mouth of the Chesapeake Bay between Cape Charles and Cape Henry.
In longitude, the spot on Virginia Beach north of the toll road road is located at 75W 58' 41" In decimal decrees, that's -75.97817, with the minus sign to show it is west of the Prime Meridian running through Greenwich.
Now test your skills - use Terraserver to discover the latitude of southeast corner of Virginia, including the latitude in decimal degrees. Go to Terraserver, search for "Virginia Beach," then click on the arrows to move south and east until it displays the edge of Virginia/North Carolina:
| Click on the "info" button: |  |
and you'll be able to see the coordinates. Note that the southeast corner of Virginia is not exactly 36 degrees, 30 minutes...
Go back to the previous page without the coordinate information, and you can switch from topo map to aerial photo:
Once again you can use the "Info" button to see the coordinate data:
