Tag: branches of surveying

What is levelling?

In the context of surveying and construction, leveling refers to the process of determining the height or elevation of points on the Earth’s surface relative to a reference point or benchmark. It is a technique used to establish and measure height differences, slopes, and contours of the land.




The leveling process involves the use of a leveling instrument, typically a level or a theodolite, along with a leveling rod or staff. Here is a general overview of how leveling is performed:

  1. Setting up the Instrument: The leveling instrument is set up on a stable tripod at a known reference point or benchmark. This point has a known elevation, usually determined through previous surveying work or government-provided benchmarks.
  2. Establishing a Sightline: The leveling instrument is adjusted and leveled so that it is perfectly horizontal. A sightline is then established by aligning the crosshairs of the instrument with a specific point on the leveling rod held at the reference point.
  3. Moving to Target Points: The leveling rod is then moved to the desired points where the elevation needs to be determined. The person holding the rod ensures it is held vertically and the instrument is focused on the rod.
  4. Reading the Elevations: The instrument’s crosshairs are aligned with the point on the rod, and the instrument’s leveling staff or a digital readout displays the difference in height between the reference point and the target point. This difference is known as the vertical distance or the height of collimation.
  5. Recording the Data: The elevations or height differences are recorded in a field book or digitally for further analysis and documentation.

By repeating this process at various points across a survey area, leveling allows for the creation of accurate topographic maps, determination of slopes and grades, and establishment of reference points for construction projects. It is an essential technique in civil engineering, construction, and land surveying for ensuring precise and reliable measurements of elevation.

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CSEE NECTA 2015 QN 6(B) ON SURVEYING

Give one reason for each of the following:
(i) Ranging pole has a pointed metal end.
(ii) Note book is important during field study.
(iii) Back bearings are taken during compass survey.
(iv) During surveying, measurements are called back by the booker

ANSWER

(i) Ranging pole has a pointed metal end: The pointed metal end of a ranging pole is used to precisely mark a specific point on the ground. This helps in accurately establishing control points or reference points during surveying. The pointed end allows for precise placement and ensures that the pole is firmly planted in the ground, reducing errors in measurements.

(ii) Note book is important during field study: A notebook is essential during field study as it serves as a record-keeping tool. Researchers and surveyors can document their observations, measurements, sketches, and other relevant information in the notebook. It helps in maintaining a systematic record of data and ensures that important details are not forgotten or lost. The notebook also serves as a reference for future analysis, interpretation, and reporting of the field study findings.

(iii) Back bearings are taken during compass survey: Back bearings are taken during compass survey to verify the accuracy of the initial bearings and to check for any errors or discrepancies in measurements. By taking back bearings, the surveyor can compare the observed bearings with the calculated or expected bearings. If there is a significant difference between the two, it indicates the presence of angular errors or magnetic disturbances that may affect the accuracy of the survey.

(iv) During surveying, measurements are called back by the booker: Calling back measurements by the booker is an important practice in surveying to ensure accuracy and prevent errors. It involves the surveyor or booker repeating the recorded measurements aloud, allowing for cross-checking and verification. This process helps in identifying any mistakes, transposition errors, or misreadings that may have occurred during the initial measurement. It acts as a quality control measure and enhances the reliability and validity of the survey data.

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