Leveling Method for Distant Points
The choice of leveling method depends on the distance between points and accuracy needs.
Reciprocal Leveling for Significant Distances
Reciprocal leveling is specifically used to determine the elevation difference between two points that are quite apart. This method is crucial because it helps minimize errors caused by instrumental collimation inaccuracies and atmospheric refraction, both of which are significant over long distances.
By performing readings from both ends of the long sight, these systematic errors are counteracted, yielding a more reliable elevation difference.
Comparison with Other Methods
- Simple Leveling: Suitable only for short distances where Earth's curvature and refraction effects are minimal. It is not appropriate for points quite apart.
- Check Leveling: This is a verification process to confirm the accuracy of previously recorded level readings, not a primary method for long-distance measurements.
- Fly Leveling: Often used for preliminary or reconnaissance surveys covering moderate distances. It might lack the precision required for very distant points compared to reciprocal leveling.
For measuring elevation differences between points that are quite apart, reciprocal leveling is the most accurate and appropriate technique.
Important Questions from Levelling
The expression for sensitivity of the bubble tube (α) can be taken as, ______
Where n = No. of divisions, s = Net staff reading, D = Distance, R = Radius of curvature, l = Length of one division
A vertical line which is perpendicular to the level line is called:
In levelling between two points A and B on the opposite sides of a river, the level was first set up near A and the staff readings on A and B were 2.645 m and 2.30 m respectively. The level was then moved near B and set up; the respective staff readings then were 1.085 m and 1.665 m on A and B respectively. What is the true difference of level between A and B?
A level, when set up $20$ m from peg A and $70$ m from peg B, reads $0.750$ m on a staff held on A and $2.065$ m on a staff held on B, keeping the bubble at its centre while reading. If the reduced levels of A and B are $100.500$ m and $101.800$ m respectively, what is the collimation error per $100.0$ m?
In levelling back, sight is also called as ______.
