CivilForge

Tape Temperature Correction

C_{T} = α L (T - T_{0}) L_{true} = L (1 + α Δ T)

Steel tape expansion coefficient α = 6.45×10⁻⁶ /°F (11.6×10⁻⁶ /°C). T0 is the standardization temperature (often 68°F). If the tape is warmer it is too long, so add C_T to the recorded length. Other taping corrections: sag, tension, and slope.

α

(1/°F)

Coefficient of thermal expansion

L

Measured (nominal) length

T

Field temperature

T_{0}

Standardization temperature

C_{T}

Temperature correction

Step-by-step solved example

A 100.000 ft steel tape is standard at 68°F and used at 88°F. Find C_T and the true length of one tape length.

A steel tape expands: length correction like a temperature slope.

1. ΔT
ΔT = 88 − 68 = 20°F.
$Δ T = 2 0^{\circ} F$
2. Correction
C_T = 6.45e−6 × 100 × 20 = 0.0129 ft.
$C_{T} = 0.0129 ft$
3. True
Tape is long: L_true = 100.013 ft (add to measured).
$L_{true} = 100.013 ft$

Answer: C_T = +0.0129 ft, L_true = 100.013 ft

10 practice questions

0/10 correct

1.Steel tape α in US customary units is

2.If T < T0 the tape is short, so you

3.L = 200.000 ft, ΔT = +15°F, α = 6.45e−6. C_T =

4.Invar tapes are used for precise baselines because α is

5.α in SI for steel is about

6.A distance recorded as 5 tape lengths of a long tape (each +0.01 ft) is too

7.Tension correction is needed when field pull differs from

8.Sag correction is always

9.T = T0 ⇒ C_T =

10.30 m steel tape, ΔT = +10°C, α = 11.6×10⁻⁶ /°C. C_T =