Methods of reliability engineering allow to anticipate an efficiency both geodetic network and single control points throughout the period of its operating. A reliability assessment of a predicted survey object behaviour produces data useful in optimisation of survey scope. timetable and accuracy. The essentials of reliability approach and procedures of finding of operational reliability characteristics have been presented in the paper. The presented characteristics include: the failure rate function ,i(/), the reliability function R(I) and the random object life F(1). Methods applied in reliability engineering viz. method of complete probability and method of evaluation of raw and parallel reliable structures have been adopted for survey purposes. Besides the standard ones original methods are also presented in the paper. Their concept lies on finding of stability functions and reliability characteristics indicated by means of statistical tests referring to density probability of predicted displacements. Although the presented theory is of general character the main application is focused on levelling networks.