Geography Reference
In-Depth Information
While maps have been used for a very long time, accurate maps of loca-
tion have only been around for some 400 years, since a way of determining
longitude was determined. Cartographers until then could only accurately
determine the latitude of places. This means that while the equator could
commonsensically be calculated as the halfway place between the north and
south poles, the 0
starting measure for longitude was only agreed to inter-
nationally in the late 19th century and placed in Greenwich, England. Up
until then, 0
°
longitudes started from different locations including Paris and
the Faro Islands. Knowing where the starting measure of longitude is located
is crucial for accurate navigation. Before there was widespread agreement
about where the starting (0
°
) longitude is for all people and countries, an
arbitrary starting longitude was fine so long as it was used systematically.
°
Roles of Projections
One of the key roles of projections has been in the production of maps for
ocean navigation, which are called “charts.” The development of accurate
ways to determine location went hand-in-hand with the growth of European
naval powers. However, because these are spherical coordinates, and mari-
ners needed f lat maps to take with them, projections became crucial. The
Mercator projection is perhaps so commonplace because a straight line in
this projection shows a constant compass bearing. You should remember
that there are many other projections, but the Mercator projection possesses
the quality that lines of a constant direction are straight lines.
Because of this character, the Mercator projection was very important
for navigation on water by compass, but other modes of transportation can
better use other projections. More recently, since airplanes began to fly regu-
larly across and between continents, another type of projection was needed
for their navigation. A line of a constant compass direction may be straight
in the Mercator projection, but this line does not show the shortest distance.
Great circle path between Minneapolis, USA, and Frankfurt, Germany. The great cir-
cle distance is 4,392 miles.
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