Question

Reduce from the datum provided.​

Answer 1

Datum

Datum is an imaginary level surface or level line from which the vertical distances of different points are measured. In India the datum adopted for the great trigonometrical survey is the mean sea level at Mumbai. Before it, it was at Karachi.

Reduced level can also be defined as:

The vertical distance of a point above or below the datum line is known as the reduced level of that point. The RL of a point May be positive or the negative according as the point is above or below the detum

The elevation of point A relative to the Mean Sea Level is called the reduced level (RL) of A.