Abstract:
The variations, along time, of the distances between object points on tunnel cross-sections
(convergences) may be used in real time continuous tunnel monitoring systems, as
decision tools, to activate signals of alert or alarm. Electronic tacheometers, especially the
motorized ones, are frequently used to measure convergences. To quantify the levels of alert
and alarm one should take into account the convergence measurement uncertainty. The paper
deals with modelling the uncertainty of the convergence as a function of the instrumental
uncertainty parameters, using the general formula for the propagation of variances. The model
is applied to a simulated tunnel, where the special case of motorized tacheometers with
automatic target recognition (ATR) systems is analysed.
