What is bench mark shifting in land surveying

This construction video tutorial presented by renowned engineer S.L. Khan, is very useful for land surveyor. The video briefly explains bench mark shifting in land surveying.

The term bench mark, or benchmark is derived from the chiseled horizontal marks that surveyors create in stone structures, into which an angle-iron is set to develop a "bench" for a leveling rod, thus making sure that a leveling rod should be properly repositioned in the equivalent place in the future. These marks are generally pointed with a chiseled arrow under the horizontal line.

The term is normally applicable to any item that is employed to demarcate a point as an elevation reference. Commonly, bronze or aluminum disks are arranged in stone or concrete, or on rods driven intensely into the earth to present a secure elevation point.

If an elevation is demarcated on a map, but there does not exist any physical mark on the ground, it belongs to a spot height.

In surveying, a "bench mark" stands for a post or other permanent mark that is set at a recognized elevation to be applied as the basis for working out the elevation of other topographical points.

Bench Mark Shifting means locating the level of a newly situated point with reference to an old acknowledged point.

To get more clear idea, go through the following video tutorial.

Video Source: SL Khan