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Height of Light Google Images41 locationsPioneer
Feb 27 2016
Picture Mountain and Picture
Featured Detail Photo mini map Featured Full Photo.: FLYING_FLIVER :.
Nov 22 2014
Margies Peak - Skull 2493
FamilyPioneer/Modern Tool
AKA "Surveyor's Wooden Staff" with wire supports
(see feature pics for representative examples)

Surveyor's Purpose / Use:
Lights were frequently used as targets for surveying observations at night. Alot of survey work was done at night to avoid the effects of heat wave distortion over long distances, which made observations taken during the day less accurate.

In order to help pinpoint a particular station, a light was suspended directly over the triangulation station, from a few feet up, to over a hundred feet in some cases, with the use of a tower. It was necessary to know the 'Height of Light', to accurately determine the correct vertical position as well as the horizontal position of the station. The hIgh towers were necessary only in relatively flat areas, in order to be visible above trees, buildings and other obstacles.

In hilly or mountainous areas, the highest possible locations for the markers themselves were selected, in order to avoid the need for towers. In many remote places, where little or no development of the land has occurred, the remains of the old wooden “Height of Light” structures are still there to be seen. The structures are either still erect with their supporting wires in place, or more likely on the ground, with the wood and wire strewn around the triangulation station sight.

Later on, collapsible modular metal towers came into use, which were assembled and disassembled on site, then transported and reused.
Since NGS (National Geodedic Survey) abandoned this 'Height of Light' technique in favor of GPS in 1984, 'Height of Light' is now just a part of surveying history.

The triangulation station's PID (Permanent IDentifier) Datasheet will note the 'Height of Light' if the surveyors used one.

Sources: NOAA (National Oceanic and Atmospheric Administration)/NGS (National Geodedic Survey) plus various benchmark forums
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