The initial measurement taken after setting up an instrument over a point. By sighting back to a previously established point with known coordinates, the surveyor orientates the instrument, setting the horizontal angle to zero or a known azimuth. In leveling, it is a rod reading taken on a point of known elevation to determine the height of the instrument.
Heard on the job
I'm set up on hub 14. Give me a backsight on hub 13 so I can zero out the gun.
Insider tip
Always check your backsight before breaking down the setup to ensure the instrument has not drifted.
Also heard as
- BS
Do not mix it up with
- Foresight: A backsight establishes the baseline from a known point, while a foresight measures a new, unknown point.