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NOAA Photo Library Image - cgs01475

A heliotrope - an instrument used to reflect sunlight for signaling purposes and to extend range of visibility between points for survey purposes. The instrument required constant attention from an operator because of the continually changing azimuth of the sun. The longest line known to have been observed with this type of instrument was 192 statute miles.

Image ID: cgs01475, NOAA's Historic Coast & Geodetic Survey (C&GS) Collection
Location: Virginia, Corbin
Photo Date: 2009
Photographer: Commander George Leigh, NOAA Corps (ret.)

Category: Coast and Geodetic Survey/

High Resolution Photo Available

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Last Updated:
November 10, 2017