change. Maps were vital instruments in determiningboundariesbetween new col-
onies and countries, in displaying and tracking demographic and economic expan-
sion, and even in promoting national andcultural identity. Maps on occasion
became tools of political propaganda, sometimes employed to illustrate an alleged
threat, or promote a territorial claim. At the same time, advances in surveying
meant that every piece of property was legally defined via a survey map, so that
accurate cartography became a crucial element of property ownership. At the
beginning of the 20th century the invention of the airplane led to the new disci-
pline ofremote sensing, adding yet another tool to assist the cartographer in mak-
ing increasingly detailed maps. Maps could be both verified and composed using
aerial photography, and the launching of data-gathering satellites after 1960 only
enlarged the universe of spatial information that cartography could express.
The modern cartographer has at his or her disposal many tools and techniques
that were unavailable to the pioneers of the field. But today’s cartographer also
has new challenges—the vast array of cartographic data produced on a daily
basis means that cartographic design is a major consideration in making maps,
and what information to leave off the map is as vital to the map’s success as what
details to include. Many different considerations must go into designing a
modern map. It is essential to base design on the potential uses of the map. This
will often determine themap projectionthat the cartographer employs. This is
important because no map is a perfect representation of reality; all maps contain
some elements of distortion. This is the case because the map, a two-dimensional
surface, cannot fully represent the three-dimensional space of the world without
presenting some degree of error. Not only must the cartographer select an appro-
priate projection for the spatial information to be conveyed, the properscale
must also be chosen. Some of these decisions will be obvious, depending on
the purpose of the proposed map. For example, a Mercator projection shows true
direction; thus, it is ideal for use when making navigational charts and maps.
But the Mercator projection distorts areas as distance increases from the equator,
meaning that if the intent of the map is toshow areal relationships in true propor-
tion, the Mercator projection is a poor choice and will convey information that is
inaccurate.
Cartographers typically must generalize the spatial data they intend to present
on a map. Exactly how this process is achieved depends on the type of information
the map should illustrate, the scale at which the information will be displayed, and
which data are the most relevant to the purpose of the map. Those designing maps
follow four steps when preparing data for presentation on a map. The first step is
simplificationof the data. In previous centuries, when accurate cartographic data
were scarce, this process was unnecessary, but with modern information-
gathering techniques, simplification is usually required to avoid cluttering the50 Cartography