Tunnel convergence monitoring
During construction, tunnels are susceptible to a gradual deformation of the already built sections. In order to follow this process and to assess its magnitude for ensuring the optimal and nearly constant tunnel cross-section, specific wall markers can be posited along the dig. Sets of markers are positioned in the sectional plane of the growing tunnel and aligned with the vertical plane connecting them. In time, markers from one set tend to drift from their initial positions disrupting the pattern of internal distances which are repeatedly measured. Tunnel outline tool enables the most accurate possible reconstruction of tunnel cross-sectional shape on the basis of the current state of an inter-marker distance set with the aid of their previous states. Since markers could become unaccountable over time, our tool allows for reconstructions from three possible set states, when the number of measurements is too small to reconstruct initial marker positions, when this number is sufficient, and when it is too big due to some distances are measured multiple times.