Height Definition: Reduced Level Explained
The question asks for the specific term used to describe the height of any point measured relative to the mean sea level.
Understanding Reduced Level
The correct term for the height of a point with respect to a reference datum, typically mean sea level, is the Reduced Level (RL).
- Reduced Level (RL): This represents the vertical elevation of a specific point above a chosen horizontal datum. Mean sea level is commonly used as the standard datum in many surveying and mapping applications. Therefore, the height of a point with respect to mean sea level is its Reduced Level.
Analyzing Other Options
Let's look at why the other options are not the correct answer:
- Bench mark: A bench mark is a physical marker or point established at a known elevation, used as a reference for surveying measurements. It is not the height measurement itself.
- Datum: A datum is the zero reference surface or point from which heights or depths are measured. Mean sea level can serve as a datum, but 'datum' itself is not the height measurement.
- Level surface: A level surface is an equipotential surface of the Earth's gravity field. It is perpendicular to the direction of gravity at all points. It's a conceptual surface, not a point's height measurement.
Therefore, the height of any point with respect to mean sea level is specifically termed the Reduced Level.
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 ______.
