Modeling of Optimal Distances of Surveying Stations for Monitoring Astable Engineering Structures Using Geodetic Methods

Large and astable engineering structures are the great importance and the behavior of such structures is usually made in Geotechnical and Geodetic methods (engineering geodesy). In the geodetic methods, the selection of appropriate surveying stations, in terms of distribution, locations, and distant of the target points to stations the control network, have a significant role in determining the accuracy of the coordinates. The optimal distance is obtained when the best accuracy is obtained to estimate the coordinates of the target points on the structure. In this research, modeling of optimal distances of surveying stations has been conducted for monitoring susceptible and unstable structures using geodetic methods. In order to determine the optimal distances, considering the maximum accuracy in determining the 3D coordinates, the accuracy of coordinate is analyzed and investigated based on the dependent variables. Then, the modeling was performed with a multivariate equation by evaluating the changes in the accuracy of the coordinate relation to the variations of the distance in different modes. The results of evaluation and validation of the proposed model using ground truth showed that the accuracy of the 3D coordinates is increased, as the distance of the target point to the structure of the body is less than the control stations. Also, the higher the subject's point height, the accuracy of 3D coordinates decreases. In addition, the proposed model show that the estimating the optimal distance, accuracy were calculated a maximum error 2.5 m in term of root-mean-square error (RMSE), which conventional adjustment results have a maximum error of 2.53 meters. Therefore, the average optimum distances using the proposed model were about 38 and 12 meters to determine the height and planimetric coordinates, respectively. If these optimal distances are observed, the best possible coordinate accuracy can be achieved in determining the coordinates of target points of engineering structures. Finally, obtained models in this research, can be used to determine the optimal distance between the mapping tools –such as total stations- to the construction, especially for monitoring the construction of high building or monitoring the Building facades with the best accuracy.