A NEW METHOD FOR DEFORMATION MONITORING USING SURVEY CONTROL NETWORKS

Abstract

The use of survey control networks is one of the most important techniques applied in deformation monitoring field. The differences in coordinates of stations (displacements) obtained from least squares adjustments are compared in order to assess if a deformation of a specified magnitude exists.

In this research the well known methods of deformation detection are reviewed. Traditionally, the global congruency test is carried out to detect if the area of the network have undergone any change in shape and, as a next step, localization methods are applied to determine deformations at specific points.

However, the localization procedures developed are rather complicated and tedious. A new method is developed to detect deformations at specific points directly without the need for further localization techniques. The procedure is used both directly and sequentially using fixed and free networks.

The results obtained from the direct application of the method are identical up to 75% when compared with those obtained from the old techniques. The sequential procedure gave results that are 100% identical to those obtained from the old methods.

Results, also, indicate that the variation of an observation more than twice its standard error leads to a detectable deformation at a level of significance greater than 0.05.

Vertical deformations can be represented graphically using contour lines. This idea is applied to detect the vertical deformations and to define the stable area using the statistical results of the new procedure.