Short Answer:

The process for height measurement in surveying is called leveling. It helps in finding the elevation or height difference between two or more points on the ground. Surveyors commonly use instruments like a dumpy level, leveling staff, or a digital level to perform this task accurately. The height of a point is measured with reference to a known point called the benchmark.

In this process, readings are taken on a staff held vertically at the desired points. By comparing these readings, the difference in height is calculated. This is useful in construction, road design, and land development to ensure level surfaces or proper slopes.

Detailed Explanation:

Process for height measurement in surveying

Height measurement, or determining the relative elevation between points, is a very important task in civil engineering and surveying. It helps engineers understand the topography of land, plan drainage, design roads, and construct buildings properly. The process is known as leveling, and it provides vertical distances of points either above or below a fixed reference level.

The process for height measurement involves a sequence of careful observations and calculations using leveling instruments and staff. The goal is to find out the elevation difference between points and determine the actual height of unknown points using known references.

Instruments Used

• Leveling Instrument: This could be a dumpy level, tilting level, auto level, or digital level. It is used to establish a horizontal line of sight.
• Leveling Staff: A graduated rod held vertically at the point where height is to be measured. It is read through the level to record the height.

Steps Involved

1. Set up the Instrument:
   The leveling instrument is mounted on a tripod and set up on firm ground between the two points. The instrument must be properly leveled using its foot screws and bubble level.
2. Take Back Sight (BS):
   A staff reading is taken on a known point or benchmark. This reading is known as the Back Sight and is the starting point for calculation.
3. Take Intermediate Sight (IS) if Needed:
   If there are multiple points between the known and unknown points, staff readings are taken at these points to know their heights.
4. Take Fore Sight (FS):
   A final staff reading is taken at the new point whose height is to be found. This is called the Fore Sight.
5. Calculate Height Difference:
   The difference in elevation is calculated as:

Elevation of New Point = Elevation of Known Point + BS – FS

If multiple points are involved, the rise and fall method or height of instrument method is used to calculate elevations step-by-step.

6. Shift Instrument (if required):
   If the distance between points is large, the level is moved, and a new BS is taken on a point with a known height. The process continues until the final point is reached.

Methods of Leveling

• Differential Leveling: Used when the points are far apart and have large height differences.
• Profile Leveling: Done along a straight line, such as a road or canal.
• Fly Leveling: Quick leveling done to connect benchmarks.
• Reciprocal Leveling: Used when obstacles like rivers lie between the points.

Conclusion

The process for height measurement in surveying ensures accurate elevation data, which is essential for designing safe and functional structures. By using leveling instruments and techniques like back sight and fore sight readings, surveyors can determine the height differences between any number of ground points. This helps in achieving correct slopes and levels for construction work.