The
Triangulation Collection contains over 150 photos depicting Coast
and Geodetic Survey activities in determining distances, latitude
and longitude, state plane coordinates, and directions between points
by the method of triangulation. The Triangulation Collection shows
observers and a variety of instruments used for observing angles of
triangles and other polygons; heliotropes used to reflect sunlight
or electric lamps for showing lights at night; the various apparatus
used to measure distances prior to the development of electronic distance
measuring devices; early electronic distance measuring instruments;
and the great towers that were part of the American landscape for
close to 150 years that allowed the geodetic surveyors to measure
angles between points tens of miles apart.
