Auto Level :
leveling instrument Used to take the surface Levels to find out the level difference of a particular area.
There are various, Levelling Instruments available -
Dumpy level - British introduced this with a telescope on a Horizontal Plate to measure levels in the same line of collimation. Used to measure levels inversely.Later Dumpy level introuduced with erect image and the size of telescope size, also reduced.
Then there introduced Quick setting Level, Tilting Level, and Automatic Levels.
Now all other models are Outdated and Only Automatic Levels are in use.
Automatic Levels: Are advanced Version of Dumpy Levels An Automatic Level has a compensator built inside to withstand wind and vehicle vibrations in the construction site. Despite of disturbance the levelling instrument comes back to its line of
collimation to some extent instead of setting the instrument time and again. Its also
more accurate while compared to Dumpy Levels. its accuracy depends on each
model of the instruments from +- 2.5mm to +-0.5mm.
There are Auto Levels from 20X magnification to 32X magnification. The 32 X
magnification can accommodate PPM ( parallel Plate Micrometer) used to measure
accuracy in 0.1mm . Usually for more precession work or Machinery Work.
Brands that are dealing Auto Levels are: 
Leica
BOSCH 
Sokkia