The research and development project GOCA (GNSS/GPS/LPS based Online Control and Alarm System) applies GNSS/GPS as well as classical local positioning sensors (LPS) such as e.g. total stations for a real-time deformation monitoring. The GOCA system may be set up as an early-warning-system for natural hazards, such as landslides, mining and tunneling activities, volcano monitoring, and also for the monitoring of geotechnical structures and buildings. The GOCA system consists of GNSS/GPS/LPS sensors, which are set up in the monitoring area as a permanent array or as a mobile monitoring system. The GOCA hardware-control and communication software modules collect in different kind of communication modes the GNSS/GPS/LPS data in a user defined sampling rate. The GOCA deformation-analysis software is responsible for a further processing of that data in a three steps sequential adjustment procedure. The 1(st) step initializes the monitoring reference frame - the coordinates and covariance matrix - consisting of stable reference points. The 2(nd) and 3(rd) step comprise the georeferencing of the three-dimensional object-point coordinates in the reference frame, and the simultaneous deformation analysis respectively. Both least squares and robust estimation techniques (L1-norm and other so-called bounded influence M-estimators) are applied. The mathematical models of the above three adjustment steps are presented. A first focus is set on the robust online displacement estimation, statistical testing and alarm setting. Further the algorithmic scheme of a L2- and a robust L1-norm Kalman filter are treated, which are related to the object-point state vector of displacements, velocities and accelerations. With respect to the deformation monitoring in geotechnics and of constructions, one of the further developments of the deformation algorithms will be set on the integration both of further parameters (e.g. material parameters, damage models), as well as of additional geotechnical sensors (e.g. strain-meters) by means of so-called system analysis, which is based on deformation FEM-approaches for static and dynamics processes. Typical project applications are shown as examples for the GOCA-system.
