display and compare any number of spatial attributes, producing an array of the-
matic maps. Technology has also increased the degree of accuracy of maps—
sophisticated Global Positioning Satellites (GPS) units are capable of locating fea-
tures to within centimeters of their actual position, resulting in maps that are the
most precise ever made. Maps are vital to our lives, as they help us find our way
to new places, fight the spread of diseases, produce more food, control damage
to the environment, and have thousands of other crucial applications. Most impor-
tantly, they provide a means of visualizing and understanding the world around us.
Map Projections
The basic problem in displaying the real world, which appears in three dimen-
sions, onto the two-dimensional surface of amapis addressed by the map projec-
tion. Because there is no way to accomplish this transformation without distorting
at least one of the basic elements indicated on the map (angles, areas, distance, and
direction), a means of projecting the information contained on the map must be
selected. Although no map can show all of these basic relationships in their true
dimensions, many projections are able to display at least one of them accurately
and truly. For this reason, it is quite important that when using a map for a specific
purpose, attention is paid to the projection of the map. Geographers and others
working with maps must be aware of the limitations of the projection they employ
to display their data, and how it may affect the spatial relationships they wish to
analyze. In theory, a limitless number ofmap projections might be constructed,
and with the development of computercartography, many options are readily
available. Today, with a click of the computer mouse the projection of a map and
the information it contains may be changed instantaneously, an option made avail-
able to geographers only in recent years. A number of projections have limited
application and are used only for highly specialized work. However, over the past
several centuries, some projections have become “standard” in the sense that they
are used more than others for certain purposes such as comparing relationships
between areas, navigating on the high seas or during transoceanic flights, or other
types of uses.
Most map projections feature a graticule, a grid of lines running in both a north-
south direction and in an east-west direction. The graticule may be based on lines
oflatitude and longitude, or can be based on some other coordinate system. The
purpose of the graticule is to provide a series of reference points and lines that may
be useful to those working with the map, but it must be remembered that the gra-
ticule typically contains the same problems with distortion and inaccuracy that
Map Projections 219