Surveying is an art of making measurements on as will determine the relative position of different points on the surface of the earth.
It is essentially a process of finding position of different points
on the horizontal plane.
Levelling is the art of determining and representing the relative heights or elevations of different points on the surface of earth.
Surveying deals with the position of points in the horizontal plane whereas Levelling
includes relative position of points in a vertical plane.
Although Surveying and Levelling are two different distinct operations.
Whereas if we see in the broader sense Then the term Surveying also includes Levelling.