How to calculate the distance using dumpy level readings?

 

Dumpy Level/Auto Level

To calculate the distance using dumpy level readings, you primarily rely on the stadia method, which uses the crosshairs on the dumpy level's telescope. Here's how it's done:

Equipment Required:

• Dumpy level

• Levelling staff (graduated rod)

Steps for Calculation:

1. Set up the Dumpy Level:

• Place the dumpy level on a tripod and adjust it so it is level using the spirit bubble.

2. Take Staff Readings:

• Aim the dumpy level's telescope at the levelling staff held vertically at the point where you want to measure the distance.

• Through the telescope, you will see three crosshairs: top, middle, and bottom stadia lines.

3. Record the Readings:

• Note down the staff readings at the top and bottom stadia lines.

4. Find the Staff Intercept:

• The staff intercept (S) is calculated by subtracting the bottom reading from the top reading:

S=Top Reading−Bottom Reading

5. Apply the Stadia Formula:

• The horizontal distance (D) is calculated using the formula:

                       D=KxS 

Where:

• D = Horizontal distance

• S = Staff intercept

• K= Stadia constant, typically 100 for dumpy levels

Therefore:

D=100×S

Final Calculation:

• Multiply the staff intercept by 100 to get the distance between the dumpy level and the levelling staff.

Example:

• Top reading = 1.5 m

• Bottom reading = 1.1 m

S=1.5−1.1=0.4 m

S = 1.5 - 1.1 = 0.4 

S=1.5−1.1=0.4m 

D=100x0.4=40 m

D = 100 x 0.4 = 40 

D=100x0.4=40m

So, the distance is 40 meters.

Comments if you need more clarification!