map with irrelevant detail. Second, the cartographer mustclassifythe data, espe-
cially if a thematic map is the goal (see theMapentry for a discussion of map
types). The type of classification system employed must be chosen with care, as
the type and number of classes may affect the appearance, and thus the interpreta-
tion, of the information on the map. The classification scheme used is usually
shown using a map legend, a separate component of the map that also illustrates
the next phase of design,symbolization. The various classes of data shown on
the map must be represented in some way. This may be accomplished using differ-
ent colors, patterns, or depending on the nature of the classification system and the
data, lines or areas. Finally, the process ofinductionmay be used to fill in gaps on
the map where data are lacking. This must be done carefully, as the cartographer is
using known data points to interpolate new data points, a process that may lead to
inaccuracies if not performed with deliberation and caution.
Technology has become enormously important to cartography. Cartographers
in the 21st century produce maps using computers, which greatly enhance both
the appearance and functionality of modern maps. Data-gathering techniques have
also become increasingly sophisticated, complex, and accurate. For example, a
Global Positioning System (GPS) can be employed to gather incredibly detailed
and positionally accurate information—some GPS receivers can record locations
of features to within centimeters of their actual location on the earth’s surface
(or above the surface, in some instances). Such detailed data, gathered so readily,
have never before been available to cartographers, and make the process of map
design and presentation even more crucial. Computer cartography also allows
much greater flexibility in the production of maps, in that a map’s classification
scheme, symbols or even scale and projection may be changed with a simple click
of a button. Previously, once a map was produced, it represented a static presenta-
tion of reality because the characteristics of the map were fixed, and could be
altered only by making and printing a completely new map. The advent of com-
puter cartography software packages, which store cartographic information digi-
tally for easy and rapid retrieval, permits the production of a host of maps from
the same data set, and makes possible the manipulation of any or all of the map’s
basic characteristics.
In fact, many maps available today arenot even produced and disseminated
using paper, but rather appear as cybermaps, which are stored in a cyberatlas,
available only on the Internet. Moreover, the appearance ofGeographic Informa-
tion Systems (GIS)has revolutionized cartography. A GIS is a database, often
containing many different types of spatial information, which may be displayed,
analyzed, and published in any combination. A large GIS may be capable of pro-
ducing thousands of different maps based on various data, or of displaying the
same data set in many different ways by changing the scale, projection,52 Cartography