Types of levelling:
1.Simple levelling:-When the difference between the two points is determined by setting the levelling instrument midway between the points the process is called simple levelling
2.Differential levelling:-Also known as compound levelling or continuous levelling.In this method,the level is sett up at several suitable positions and staff readings are taken at all if these.
This method is adopted when(i)when points are a great distance(ii)difference of elevation between points is large(iii)obstacles between the points.
There are other types like fly levelling,check levelling,profile levelling etc...
Levelling instruments:Level(Auto level,Dumpy level,Wye level etc...),Levelling staff