In surveying, the term 'levelling' refers to what process?

Levelling in surveying is fundamentally concerned with establishing elevations, which involves determining the height of points in relation to a reference point, typically referred to as a benchmark. This process is crucial in creating a level surface and ensuring that other measurements, such as distances and angles, are accurately understood in the context of their vertical position. By establishing elevations, surveyors can create topographic maps, assess land drainage patterns, and set construction layouts, among other tasks.

Calculating distances, determining angles, and measuring areas are essential survey practices, but they pertain to different aspects of the surveying process. These tasks deal with the horizontal aspects of the terrain rather than focusing on vertical height and its implications. Hence, the primary definition of levelling directly aligns with the process of establishing elevations in surveying.