96 THe geOgRaPHiC anD CaRTOgRaPHiC FRaMeWORK
Universal Transverse Mercator Coordinate system
The Universal Transverse Mercator Coordinate System (UTM), like latitude and lon-
gitude, is used to pinpoint locations on the earth. The UTM grid was developed by
the U.S. Army in the 1940s and is based on the transverse Mercator projection. The
system divides the earth into 60 zones that are 6° of longitude wide. Each zone is
centered on a meridian. The zones are numbered from 1 to 60 beginning at 180° and
going eastward. Thus, Zone 1 goes from 180° to 174°W and is centered on 177°W
(Figure 6.5).
Each longitude zone is divided into 20 latitude zones. Each of these zones is 8°
from north to south. Latitude zones begin at 80°S and extend to 84°N. The last zone
is extended 4° so that the northern-most lands are covered. The latitude zones are
given letters beginning with “C” in the south and continuing to “X” in the north.
The letters “I” and “O” are not used because they can be confused with the num-
bers one and zero. “A,” “B,” “Y,” and “Z” are used for portions of the Antarctic
and Arctic areas. The grids formed are referred to by the longitude number and the
latitude letter with longitude first. Thus, Los Angeles is in Zone 11S and New York
is in Zone 18T.
A place on earth is pinpointed by the longitude zone and an
easting and
northing
coordinate pair. Easting is the distance of the point from the central meridian of the
longitude zone and northing is the distance of the point from the equator. Distances
are in meters.
state Plane Coordinate system
The State Plane Coordinate System (SPS or SPCS) shown in Figure 6.6 is widely used
by state and local governments and is considered more accurate than the UTM sys-
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11
12
13
14
15
16
17
18
19
126°W 120° 114° 108° 102° 96° 90°
84°
78°
72°
66°W
T
S
R
