United States National Grid

The United States National Grid, officially known as the United States National Grid for Spatial Addressing (USNG), is a system of geographic grid references commonly used in United States, different from using latitude or longitude. It is similar in design to the national grid reference systems used throughout other nations. The USNG was developed by the Federal Geographic Data Committee.

Overview

The purpose of the USNG, as defined by the DHS, is to "create a more interoperable environment for developing location-based services within the United States and to increase the interoperability of location services appliances with printed map products by establishing a nationally consistent grid reference system as the preferred grid for NSDI applications. The U.S. National Grid is based on universally-defined coordinate and grid systems and can, therefore, be easily extended for use world-wide as a universal grid reference system." [http://www.fgdc.gov/usng/usng/20050701_ESRIUser_USNGintro.pdf]

It resembles the Military Grid Reference System (MGRS). When the WGS84 datum is used, USNG and MGRS coordinates are practically identical.

In addition, it has the advantage of being easily plotted on USGS topographic maps by using a simple "left to right and then up" method instead of having to plot "backwards" from right to left when using latitude and longitude in the Western Hemisphere. The coordinates are also easily translated to distance as they are actually in meters. Thus the distance between two coordinates can quickly be determined in the field.

You can download USNG 1 km² grid state-wide polygons for select states at http://mississippi.deltastate.edu. The site also gives more detailed information about the US National Grid.

See also

* British national grid reference system
* Irish national grid reference system

References

* FGDC, "United States National Grid (USNG)", December 2001, Reston, Virginia, [http://www.fgdc.gov/standards/projects/FGDC-standards-projects/usng/fgdc_std_011_2001_usng.pdf 1 megabyte PDF]

External links

* [http://www.fgdc.gov/usng USNG homepage]
* [http://www.fgdc.gov/usng/how-to-read-usng/index_html How to Read a United States National Grid (USNG) Spatial Address]
* [http://www.ngs.noaa.gov/cgi-bin/usng_getus.prl Utility to convert latitude and longitude to USNG]
* [http://www.fidnet.com/~jlmoore/usng Demonstration of USNG on a Google Map]