Propagation of refraction errors in trigonometric height traversing and geodetic levelling

Description

The use of trigonometric height traversing as an alternative to geodetic levelling has recently been given considerable attention. A replacement for geodetic levelling is sought to reduce the cost and to reduce the uncertainty due to the refraction and other systematic errors. As in geodetic levelling, the atmospheric refraction can be the main source of error in the trigonometric method. This thesis investigates the propagation of refraction errors in trigonometric height traversing. Three new models for the temperature profile up to 4 m above the ground are proposed and compared with the widely accepted Kukkamäki’s temperature model. The results have shown that the new models give better precision of fit and are easier to utilize. A computer simulation of the influence of refraction in trigonometric height traversing suggests that the accumulation of the refraction effect becomes randomized to a large extent over long traverses. It is concluded that the accumulation of the refraction effect in short-range trigonometric height traversing is within the limits of Canadian specifications for first order levelling.