Heliotrope (instrument)
Videos
The heliotrope is an instrument that uses a mirror to reflect sunlight over great distances to mark the positions of participants in a land survey. The heliotrope was invented in 1821 by the German ma
Heliotrope (c. 1878): B.A. Colonna collection (NOAA). This may be the very one Colonna surveyed from 192 miles away.
Gauss's Heliotrope (c. 1822)
Wurdemann's Heliotrope (1866)
Coast Survey, Steinheil, and simple heliotropes c. 1898
Retroreflector
Videos
A retroreflector is a device or surface that reflects light or other radiation back to its source with minimum scattering. This works at a wide range of angle of incidence, unlike a planar mirror, whi
Heliotrope (instrument)
…American military specification for heliotropes (MIL-H-20194E) was retired on 8 December 1995. Surveyors used the heliotrope as a specialized form of survey target; it was employed during large triangulation surveys where, because of the great distance between stations (usually twenty miles or more), a regular…
A gold corner-cube retroreflector (made with three orthogonally joined flat mirrors)
Eyeshine from retroreflectors of the transparent sphere type is clearly visible in this cat's eyes.
"Aura" around the shadow of a hot-air balloon, caused by retroreflection from dewdrops
Car with reflective stickers