Robustness analysis of 3D networks

Traditionally, 3D geodetic networks are established as unions of horizontal and vertical control networks. However, over the last 10 years or so, GPS (Global Positioning System) networks have gained more and more importance. After geodetic networks are monumented, relevant measurements are taken, and point coordinates for the control points are estimated by the method of least squares. However, the method of least squares does not give any information about the robustness of networks. To measure robustness of a network, the deformation of individual points of the network is portrayed by strain. This technique is independent of adjustment constraints and reflects only the network geometry and accuracy of the observations. Furthermore, threshold values are needed to quantify the robustness of the network. If the displacements of some points of the network are worse than the threshold values, this suggests that we should redesign the network by changing the configuration or improving the measurements until we obtain a network of acceptable robustness. This paper describes how to obtain the displacements at the individual points of a 3D network, employs the specifications of Geodetic Survey Division to derive the acceptable values and shows the results on two different GPS networks.