List three methods that can be used when carrying out basic levelling?

1. Spirit levelling: This method involves using a spirit level to determine the difference in height between two points. The instrument is placed on a horizontal surface and the bubble in the level is used to ensure that the surface is level. The difference in height between the two points can then be calculated based on the position of the bubble.

2. Differential levelling: This method involves using a levelling instrument, such as a dumpy level or a digital level, to measure the difference in height between two points. The instrument is set up at one point and a staff is held at the other point. The instrument is then used to measure the height difference between the two points.

3. Trigonometric levelling: This method involves using trigonometry to calculate the difference in height between two points. This method is often used when it is not possible to physically measure the height difference between the two points, such as when there are obstacles in the way. Trigonometric levelling involves measuring the horizontal distance between the two points and the vertical angle between them, and then using trigonometry to calculate the height difference.

1. Single Leveling
2. Rise and Fall Leveling
3. Differential Leveling