CIVIL ENGINEERING FORMULAS

180 CHAPTER SEVEN

For ordinary taping, a tape accurate to 0.01 ft (0.00305 m) should be used. The
tension of the tape should be about 15 lb (66.7 N). The temperature should be
determined within 10°F (5.56°C); and the slope of the ground, within 2 percent;
and the proper corrections, applied. The correction to be applied for tempera-
ture when using a steel tape is

(7.6)

The correction to be made to measurements on a slope is

(7.7)

or (7.8)

or (7.9)

whereCttemperature correction to measured length, ft (m)
Chcorrection to be subtracted from slope distance, ft (m)
smeasured length, ft (m)
Ttemperature at which measurements are made, F (C)
T 0 temperature at which tape is standardized, F (C)
hdifference in elevation at ends of measured length, ft (m)
slope angle, degree

In more accurate taping, using a tape standardized when fully supported through-
out, corrections should also be made for tension and for support conditions. The cor-
rection for tension is

(7.10)

The correction for sag when not fully supported is

(7.11)

whereCptension correction to measured length, ft (m)
Cssag correction to measured length for each section of unsupported
tape, ft (m)
Pmactual tension, lb (N)
Pstension at which tape is standardized, lb (N) (usually 10 lb) (44.4 N)
Scross-sectional area of tape, in^2 (mm^2 )
Emodulus of elasticity of tape, lb/in^2 (MPa) [29million lb/in^2 (MPa) for
steel] (199,955 MPa)
wweight of tape, lb/ft (kg/m)
Lunsupported length, ft (m)

Slope Corrections

In slope measurements, the horizontal distance HLcosx, where L
slope distance and xvertical angle, measured from the horizontal—a simple

Cs

w^2 L^3

24 Pm^2

Cp

(PmPs)s

SE

h^2 /2s approximate

0.00015s 2 approximate

Chs (1cos ) exact

Ct0.0000065s(TT 0 )