Unstable Object Points during Measurements—Deformation Analysis Based on Pseudo Epoch Approach

Abstract

Deformation analysis or point movement checking is the basis for monitoring ground or engineering structures. There are several approaches to conducting deformation analysis, which differ from each other in measurement techniques or data processing. Usually, they are based on geodetic observables conducted in at least two epochs. As such measurements are not “immediate”, it might so happen that a point (or some points) displaces during measurement within one epoch. The point movements might be continuous or sudden. This study focuses on the latter case, where rockburst, mining damages, or newly formed construction faults might cause displacement. To study this, an observation set consisting of measurements performed before and after point displacements is needed. As the actual observation division stays unknown, this can be called pseudo epochs. Such a hypothetical observation set requires special estimation methods. In this work, we examined Msplit estimation and robust methods. The first approach’s advantage is that it provides two variants of the network point coordinates (before and after point movements), hence showing dynamic changes in the geodetic network. The presented empirical analyses confirm that Msplit estimation is a better choice that results in better and more realistic outcomes.

Keywords

• displacement analysis
• pseudo epochs
• M_split estimation
• robust estimation
• Monte Carlo simulations