tion networks, to illustrate tourist destinations, and to serve other popular
forms of communication. The third exception, globes, is the only non-
projected way of showing things, events, and relationships without the distor-
tion of projections.
A Brief History of Projections
The reasons for using projections go back to desires to accurately represent
the spherical surface of the earth on f lat maps. For geographic information
and a map to be useful, the locations and relationships must be accurate. A
nonprojected map using latitude and longitude coordinates, or an advertis-
ing map showing simple directions, is limited by its inaccuracy. You can use a
map to the new amusement park to find your way, even if you're not from
the area, but you can't use it to discover and understand the relationship of
the amusement park to things and events not shown on the maps. Impor-
tantly, because of the curved surface of the earth, surveys of larger areas
showing locations and sizes of things and events would be inaccurate. The
Euclidean geometrical measure of the earth, which is the most common
geometry—already practiced by the ancient Egyptians—cannot take curvature
into account, but must be performed in a Cartesian coordinate system that
has already taken the spherical shape of the earth into account. Further,
using projections makes it easier to compare geographic information and
maps of the same area because they provide a framework for people and
organizations to systematically locate things and events.
As you can probably already imagine, it is no surprise that the first maps
were based on work by geographers who were locating things. Ptolemy
(c. 100-168) wrote the topic Geography with the location of cities, coasts, and
other important places of the world known to the ancient Greeks. The
Romans used this topic for making a map that was ultimately lost, but it was
re-created in the 15th century.
Latitude and longitude lines.