Random or Accidental Errors:

Random or Accidental errors could occur because of lack of perfection of human eye and or human behaviour. Even the best and well-organized surveyor could have fatigue effect after working for long duration in strenuous environment causing observational errors. A random error cannot be eliminated entirely, whatever precautions are undertaken. These might, therefore, occur in either direction and thus, tend to compensate and, thus, are not serious in nature. These generally follow the law of chance and, therefore, could be analysed with the help of probability theory. Using suitable probability distribution functions, these errors can then be adjusted, distributed between several measurements and accounted for.  Each surveying method or procedure could be assigned a reliability factor (or risk factor) for accuracy depending on the analysis of probability behaviour.