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same between corners and that seconds are usually not shown if they are 00.

Notice also that each edge of the map covers 7-l/2 minutes of longitude or
latitude.
Remember, because the United States is west of the prime meridian and
north of the equator, all longitude coordinates are west (W) and all latitude
coordinates are north (N). Notice that the longitude numbers increase from right

to left and that the latitude numbers increase from bottom to top.
The longitude and latitude grid is very useful for locating a map on the globe
and for designating quadrants on a map. However, for specifying the location of a

particular point on a topographic quadrangle map, longitude and latitude can be
cumbersome because the 7 l/2- minute map shows only four marked lines each of
longitude and latitude. It is difficult to quickly and accurately estimate the
longitude and latitude of points that lie between the marked lines.

UNIVERSAL METRIC GRID (UTM)
An easier-to-use grid system for specifying a point on a topographic
quadrangle map is the Universal Metric Grid or UTM. The Universal metric grid

system is based on the Universal Transverse Mercator map projection (hence the
name ‘UTM’) between 80˚ N and 80˚ S, and on the Universal Polar Stereoscopic
projection between 80˚ and each pole. This grid system subdivides the map region
into one-kilometer squares. Each marked UTM line on the map is exactly 1000

meters (1 kilometer) to the north or east of the last UTM line. Each UTM line has
a number designation based on its distance from a reference point. One does not
need to know where these reference points are to use the UTM grid. It is sufficient
to specify the name of the map being used and the UTM coordinates read from

the map to locate a particular point. Points that fall between the marked UTM grid
lines can be accurately located by using the 1000-meter scale bar found at the
bottom of the map.

READING UTM COORDINATES ON A TOPOGRAPHIC MAP
UTM lines are marked on the margins of USGS topographic quadrangle
maps as small, blue tick marks with numbers beside them (Figure 2.3). Newer
versions of these maps also include black gridlines drawn across the face of the

map.
The upper-left and lower-right corners of the map show the full UTM
coordinates. These numbers are read simply as numbers of meters east or north of

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