Different methods for adjustment levelling and gravity net work

Every measured quantity, however carefully the observation may be made, contains errors which are due to a variety of causes. Experience shows that repea te d measures of the same quantity, wh en made under the same conditions and with the same care,do not give the same result.The difference between a measurement and the true value of the quantity measured is the true error 6f that measurement. The true value of a quantity measured is never known, and hence the true error Can never be known.The degree of precision of a measurement depends upon the method and instruments employed, and upon other conditions surrounding the survey. It isdesirable that all measurements be made with high precision, but the increase in precision is usually ace ompa nrl e d by more than a directly proportionateincrease in the cost of a survey and the time and labour of the surveyor~ therefore, one of the important functions of a surveyor is to securemeasurements which are correct within certain limits of error prescribed by the nature and purpose of