Geography Reference
In-Depth Information
General reference:
18SUJ23480647—precision 10 m
Special application:
18SUJ2348316806479498—precision 1 mm
The U.S. geographic area is divided into 6-degree longitudinal zones
designated by a number and 8-degree latitudinal bands designated by a let-
ter. Each area receives a unique alphanumeric Grid Zone Designator
(GZD)—for example, 18S. Each GZD 6
8 degree area is divided into a sys-
tematic scheme of 100,000-m squares where a two-letter pair identifies each
square—for example, UJ. A point position within the 100,000-m square shall
be given by the UTM grid coordinates in terms of its easting (E) and north-
ing (N). The number of digits specified the precision:
×
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 m
18SUJ23480647
Locates a point with a precision of 10 m
18SUJ2348306479
Locates a point with a precision of 1 m
Universal Transverse Mercator
The Universal Transverse Mercator (UTM) grid was developed in the 1940s
by the U.S. Army Corps of Engineers. In this coordinate system, the world is
divided into 60 north-south zones, each covering a strip 6
wide in longi-
tude. These zones are numbered consecutively beginning with Zone 1,
between 180
°
°
and 174
°
west longitude, and progressing eastward to Zone 60,
between 174
east longitude. The conterminous 48 United States
are covered by 10 zones, from Zone 10 on the West Coast through Zone 19
in New England. In each zone, coordinates are measured north and east in
meters. The northing values are measured continuously from zero at the
equator, in a northerly direction. To avoid negative numbers for locations
south of the equator, the equator has an arbitrary false northing value of
10,000,000 meters. A central meridian through the middle of each 6
°
and 180
°
zone is
assigned an easting value of 500,000 meters. Grid values to the west of this
central meridian are less than 500,000; to the east, more than 500,000.
°
Other National Grids
Most countries in the world have one or more national grids, analogous to
the U.S. system. In the world there are thousands of these systems. The fol-
lowing examples are exemplary for different approaches to organizing coor-
dinates. The United Kingdom, for example, has a hierarchical system that
begins with a grid of 100 100-km cells, identified by two letters. Each 100-km
cell is further divided into 100 10-km grid cells. A 10-km grid cell is further
divided into 100 1-km grid cells. Germany uses a system similar to UTM, but
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