GEODESY
Since ancient times, man has made measurements in an attempt to determine the exact size
and shape of the earth. Additionally, maps of the known world have been created
for use in navigation.
Today the need to determine the exact size, shape, and motions of the earth are
important nationally and internationally in planning, shipping and
transportation, and space exploration. The creation of map
projections is a subject of geodesy. To enable users to tie maps together,
monumented points with known coordinates are created. These points are used to
control projects in
aerial, boundary,
construction, and hydrographic
surveys.
Geodesy is the field that explores the exact size, shape, and
motions of the earth. In this process, geodesists create a network of monumented
points on the earth's surface with known coordinates. In the past these
coordinate systems have been locally derived, but with the advent of
international travel and space exploration, world-wide coordinate systems have
been created.
Part of the study of geodesy are the fluctuations in strength
the earth's gravitational and magnetic fields. These fluctuations affect several
areas of study as well as other branches of surveying. The two images below are
maps of the earth's gravitational and magnetic fields.
Gravitational map of earth. |
Map of the Earth's magnetic declination in 1995. |
Traditionally, these coordinate systems were
created by observing the stars. Today,
the Global Positioning System (GPS) is used to determine
precise positions of these monuments. This system of 24
satellites creates a network of precisely known positions orbiting the earth.
Using signals broadcast from these satellites, precise positioning, navigation,
and timing are possible.
Geodesist work closely with all branches of surveying, and
other professionals such as geophysicists. They require knowledge in upper-level
mathematics and physics to define and create models of the earth. In fact,
the mathematical fields of calculus and differential equations were created to
help model the Earth's gravitational field.
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