The main use of the Abney Level in surveying is to determine the

The Abney level (also called a clinometer or Abney clinometer) is a surveying instrument primarily used to measure the angle of inclination (slope angle) of a surface or the angle of elevation/depression between two points.

It consists of a sighting tube, a bubble level, and a graduated arc. The surveyor looks through the tube at a target point, adjusts the bubble level until it is centred (visible in the tube), and then reads the angle from the graduated scale. This gives the vertical angle between the line of sight and the horizontal.

The Abney level is particularly useful for:

• Measuring the gradient (steepness) of slopes in the field.
• Estimating heights of hills or buildings when combined with distance measurement.
• Preliminary surveys where a rough measurement of slope is sufficient.

It does not directly measure area coverage (which requires planimeters or chain/offset methods), spot heights (which need levelling instruments such as the dumpy level), or relative location (which requires compass bearings or GPS).