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.
In Figure 1-19, the instrument would be set up at instrument position one (IP1); a backsight would be taken on benchmark one (BM1) and a foresight on the turning point (TP).
Backsight. A point to be used to determine the placing and/or elevation of the surveying instrument.
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.
Nevertheless, after adjusting the coordinates of the direction point (backsight point) of the baseline, the direction angle may change.
Note that when the instrument is set up halfway between the two stations, Figure 5-9, the error between the rod reading and horizontal is the same in the backsight as in the foresight.
Height of Instrument--The elevation of the line of sight of a surveying instrument, which is obtained by adding the backsight to the elevation of a known point.
Tenders are invited for Tender For Ic Ramp Backsight (Icr-1253)
Note that the true foresights are stations that are paired with backsights. The note keeper must remember that the first backsight and the last foresight are also a pair.
In surveying, the parts of an angle are called the backsight, the vertex, and the foresight.
Tenders are invited for Supply of Ic Ramp Backsight (Icr-1253)