backsight


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backsight

[′bak‚sīt]
(engineering)
A sight on a previously established survey point or line.
Reading a leveling rod in its unchanged position after moving the leveling instrument to a different location.
(navigation)
A marine sextant observation of a celestial body made by facing 180° from the azimuth of the body and using the visible horizon in the direction in which the observer is facing.

backsight

In surveying, a sight on a previously established survey point or line.
References in periodicals archive ?
How to look backward and forward through backsight forethought.
Needless to say, for the practical purpose of laying a foundation, some sort of sightline on the ground would have to have been established, perhaps using a front and backsight of some kind, but as a means of gauging the location of the pole the kind of device I am positing could conceivably have been employed.
It had a heavier barrel that was exposed at the muzzle, a different front sight block, two-piece striker mechanism, longer stock, more robust backsight, etc.
In the laser rangefinder interface, backsight and foresight functions were added for enhanced data collection in obstructed situations.
Tenders are invited for Supply of Ic Ramp Backsight (Icr-1253)
Fundamental is that the exact position of the backsight structure must itself have been chosen, after careful observation of the celestial phenomenon concerned, in relation to the horizon mark.
A third hypothesis is that Maeshowe, unlike Newgrange, might in addition have had a useful working alignment with the capacity to detect midwinter's day itself; the tomb would then have been built in a spot where it could serve as the backsight for a long alignment towards some distant mountain peak or horizon notch.
A reassessment of the high precision megalithic lunar sightlines, 1: backsights, indicators and the archaeological status of the sightlines, Archaeoastronomy 4: S21-S40.