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Geodetic Toolkit: USNG |
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The national grid will improve public safety, commerce, and aid the casual GPS user with an easy to use
geoaddress system for identifying and determining location with the help of a USNG gridded map and/or a USNG
enabled GPS system. Although the USNG can provide for what ever level of precision desired, users may prefer to
use the UTM format for applications requiring precision greater than 1 meter.
How to read USNG coordinates.
Grid Zone Designation. The U.S. geographic area is divided into 6-degree longitudinal zones designated by a number and 8-degree latitudinal bands designated by a letter. Each area is given a unique alpha-numeric Grid Zone Designator (GZD) (i.e. 18S).
100,000-meter Square Identification. Each GZD 6x8 degree area is covered by a specific scheme of 100,000-meter squares where each square is identified by two unique letters. (i.e. 18SUJ - Identifies a specific 100,000-meter square in the specified GZD).
Grid Coordinates A point position within the 100,000-meter square shall be given by the UTM grid coordinates in
terms of its Easting (E) and Northing (N). An equal number of digits shall be used for E and N where the number
of digits depends on the precision desired in position referencing. In this convention, the reading shall be from
left with Easting first and then Northing.
Examples:
18SUJ20 - Locates a point with a precision of 10 km
18SUJ2306 - Locates a point with a precision of 1 km
18SUJ234064 - Locates a point with a precision of 100 meters
18SUJ23480647 - Locates a point with a precision of 10 meters
18SUJ2348306479 - Locates a point with a precision of 1 meter
The number of digits in Easting and Northing can be varied, depending on specific requirements or
application.