levelling by rise and fall method

Rise and Fall method is a foundational technique in surveying, employed to ascertain variations in elevation across a construction site or plot of land. This method plays a pivotal role in establishing accurate levels, ensuring the stability and precision of construction projects. Below, we delve into the intricacies of this method.

Establishing a Benchmark

The initial step involves the establishment of a benchmark, a predefined point with a known elevation. This benchmark serves as the reference point for all subsequent level measurements, providing a reliable starting point for the survey.

Taking Measurements

Surveyors traverse the site, taking precise measurements of the height relative to the benchmark. These measurements are meticulously recorded, forming the basis for subsequent calculations.

Calculation of Rise and Fall

By computing the disparity in elevation between each point and the benchmark, surveyors classify the results into “rises” (higher than the benchmark) and “falls” (lower than the benchmark). These values are meticulously documented for further analysis.

Incorporating Corrections

To account for potential errors or discrepancies in the measurements, corrections are applied. These adjustments may encompass factors such as instrument inaccuracies, atmospheric conditions, and other variables influencing the readings.

Summation and Analysis

The culmination of the process involves aggregating all individual rises and falls. This aggregate value encapsulates the overall elevation change observed across the surveyed area, providing critical data for the construction project.

Closure Verification

Surveyors conduct a thorough assessment to validate the accuracy of the measurements, ensuring that the sum of all rises and falls approaches zero. This crucial step confirms the reliability of the gathered data.

Documentation and Record-Keeping

Comprehensive records are maintained, encompassing all measurements, calculations, and any applied corrections. This dataset serves as a vital foundation for crafting precise construction plans and serves as a reference point for future endeavors.

Advantages of the Rise and Fall Method

Precision

When executed with precision, the rise and fall method yields highly accurate elevation data.

Versatility

Its applicability extends across diverse terrains and construction sites, making it a versatile tool in the surveyor’s arsenal.

Cost-Effectiveness

In comparison to more advanced surveying techniques, the rise and fall method proves to be an economical choice.

Instrument Precision

The accuracy of measurements is contingent on the precision of the surveying instruments employed.

Terrain and Site Conditions

Particularly rugged or inaccessible terrains may pose challenges for the application of this method.

Conclusion

The Rise and Fall method remains a cornerstone of traditional surveying, finding continued relevance in contemporary construction projects where precise elevation measurements are paramount. In modern surveying practices, electronic instruments and advanced software may complement this technique, enhancing both accuracy and efficiency.

rise and fall levelling

Total stations” by OregonDOT is licensed under CC BY 2.0.

The Following readings was taken with a level staff of 4m, BM =100.

2.375, 1.73, 0.615, 3.45, 2.838, 2.070, 1.835, 0.985, 0.435, 1.630, 2.255 and 3.630 m.

The instrument was shifted after the 4th & 8th readings.

steps to find RL

  • write all the given data BS, IS and FS reading.

BS = first reading taken, (initial point/after changing instrument position)

IS = all the readings taken between BS and FS

FS = last reading taken before changing the instrument position.

  • calculate the difference between corresponding readings.

Difference = BS-IS, IS-FS, FS-BS

  • Differentiate the Rise and Fall value.

Rise= if difference value is positive

Fall = if difference value is negative

  • calculate the RL value

first RL = BM

RL = RL+difference

add the corresponding RL value with diffrence value to get new RL.

  • Check for errors by using arthmetic check formula –

Sum of BS – Sum of FS = Sum of Rise – Sum of Fall = Last RL – First RL

StationBSISFSDifferenceRise (+)Fall (-)RLRemarks
12.375100BM =100
21.730.6450.645100.645
30.6151.1151.115101.76
42.8383.45-2.8352.83598.925CP -1
52.070.7680.76899.693
61.8350.2350.23599.928
70.4350.9850.850.85100.778CP -2
81.63-1.1951.19599.583
92.255-0.6250.62598.958
103.63-1.3751.37597.583
Sum∑BS = 5.648∑FS = 8.065∑Rise = 3.613∑Fall = 6.03

Arithmetic Check

Sum of BS – Sum of FS = Sum of Rise – Sum of Fall = Last RL – First RL

Sum of BS – Sum of FS Sum of Rise – Sum of Fall Last RL – First RL
5.648 – 8.0653.613 – 6.0397.583-100
-2.417-2.417-2.417

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