What is inverted staff reading?

 

What is inverted staff reading?

To obtain the reduced levels of these points, the staff is held upside down in an inverted position with its base on the elevated points. 

When booking an inverted staff reading, it is entered into the levelling table with a minus sign, the calculation proceeding in the normal way taking this sign into account.

It may be necessary to determine the heights of points such as a ceiling or the soffit of a bridge, underpass or canopy. Usually, these points will be above the plane of collimation of the level.

Example:

Find the height of the points in Figure

 

Solution:

Station	Staff Reading		H.I	R.L	Notes
	B.S	F.S
A	0.174		33.724	33.550	B.M
B	0.738	2.111	32.351	31.613	C.P
C	-1.603	-3.890	34.638	36.241	C.P
D	1.505	1.440	34.703	33.198	C.P
E		-2.192		36.895
	∑=0.814	∑=-2. 531

                ∑𝑩𝑺 −∑𝑭𝑺 = 𝑹𝑳𝒍𝒂𝒔𝒕 – 𝑹𝑳𝒇𝒊𝒓𝒔𝒕

                    𝟎. 𝟖𝟏𝟒 − (−𝟐. 𝟓𝟑𝟏) = 𝟑𝟔. 𝟖𝟗𝟓 − 𝟑𝟑. 𝟓𝟓𝟎

                        𝟑. 𝟑𝟒𝟓 = 𝟑. 𝟑𝟒𝟓