Question

The permissible error (E) for the Precise levelling type with distance (D) in kilometre is given by:
1. E = ± 0.025√D
2. E = ± 0.100√D 
3. E = ± 0.012√D
4. E = ± 0.006√D

Answer 1

Correct Answer - Option 4 : E = ± 0.006√D

Concept:

The precision of leveling is ascertained according to the error of closure. The permissible limit of closing error depends upon the nature of the work for which the leveling is to be done. The permissible closing error may be expressed as, \(\text{E} = \text{C}\times\sqrt{D}\)

Where,

E = the error in metres,

C = the constant, the value of which depends upon the type of instrument, nature of the country, atmospheric conditions and care and judgement of the level man  

D = distance in kilometre

• Rough levelling: \(\text{E} = \pm\text{0.100}\times\sqrt{D}\)
• Ordinary levelling: \(\text{E} = \pm\text{0.025}\times\sqrt{D}\)
• Accurate levelling: \(\text{E} = \pm\text{0.012}\times\sqrt{D}\)
• Precise levelling: \(\text{E} = \pm\text{0.006}\times\sqrt{D}\)