How you go about finding your latitude and longitude depends to some extent on whether you want to know your 4-digit grid square or your 6-digit grid square. Finding a 6-digit grid square requires considerably more precision in latitude and longitude. The 4-digit grid squares covers a pretty big area, while the 6-digit grid square is fairly small. The actual size of a grid square depends on the particular location, as the 1° of longitude represents different distances at different latitudes; longitude lines are closer together at the Earth's poles than at the equator.

The first step, then, is finding your latitude and longitude as accurately and precisely as you can. There are several common methods for doing so:

• Use a topographic (or topo) map. These maps contain both elevation data, by means of countour lines, and location via coordinate systems. Topo maps of US areas are available from the US Geological Survey (USGS). The most useful series of maps for finding latitude and longitude are the 7.5-minute maps, each of which covers an area of 7.5 minutes of longitude by 7.5 minutes of latitude. Most of these are at a scale of 1:24,000 (1 inch = 24,000 inches, or 2,000 feet).

For a database of USGS New Mexico Map Products These maps usually include two coordinate systems to define location. One system uses latitude and longitude-- this is what we want. The other system is the universal transverse mercator (UTM) system that consists of squares 1 kilometer on a side. For finding your grid square, use only the latitude and longitude system.  See Grid Squar Calculator

To obtain the 7.5-minute map that covers your location, you need to determine the reference code, map name and state. You'll find this information in the map index for your area. Contact USGS for information about pricing and how to order topo maps.

Many outdoor, sporting-goods and camping stores also sell USGS 7.5-minute maps. Check your local Yellow Pages.

• Use a Global Positioning System (GPS) receiver.
  With the growing number of hams using GPS Receiver Systems this is perhaps the quickest and most accurate means of determining your latitude and longitude. Check in your area for hams using GPS SYSTEMS.

• Call the local library or town hall. They'll often know their own latitude and longitude. If you don't live too far away from the library or town hall, that may be sufficient.

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