Abstract
The root mean square error expressed by the formula
m=±√1/4n[dd/R]
has been generally used to estimate the accuracy of precise leveling. This formula is based on the assumption that forward and reverse levelings of a section should be independent each other and they should be of the same accuracy, and that a sum of differences between the two levelings along a route should be zero.
However, there are many cases in which survey results do not satisfy this assumption. The sum of the differences often deviates appreciably from zero.
In this paper, other methods of estimating the leveling accuracy are examined in which correlations between readings are taken into consideration. The methods are applied to the leveling results in the Tokai area . The results show that the correlation coefficient between forward and reverse measurements is practically zero whereas that between right and left graduation readings is about +0.4 and the total error of the precise leveling is estimated as about ±0.5 mm/km.
