No abstract

The concept of obtaining uniform and high-precision 3D models of large and complex engineering structures based on terrestrial laser scanning surveys highly depends on the accuracy of registering a series of adjacent scans. If it is not possible to place the required number of reference points in the observation scene, and there are no identifiable structural elements that could serve as such reference points, the issue can be solved by using the virtual reference points. The virtual reference points are not marked, but their position can be re-created in the post-processing of the scans on the basis of the geometrical features of the object. In the case of an industrial chimney, these can be the structural axis points determined at arbitrarily selected altitudes. In the solution presented herein, the coordinates of the reference points were independently determined twice: in the geodetic coordinate system using traditional method, in the local system of the scanner using the bisector of the chord of the circle, and by approximation of the circular arc shape of the chimney shell. Both procedures are preceded by the filtration of outliers. The concept of virtual reference points was verified by the measurement of the verticality of the axis and the structural geometry of a steel industrial chimney, which was accessible only on the foundation level.

Horizontal control networks established with monuments are functional if the conditions related to the number of control points, their density, condition and stability of coordinates are met. For functionality defined in those terms, deterministic accuracy characteristics are of little use. The subject matter discussed herein includes the two key features of geodetic control points, i.e., usability and stability. Due to the varying properties of those variables and the impact of the operating time of the system, there is no alternative to reliability-based approach in developing the functionality model. The measures of functionality and the procedures of data acquisition for developing the model of the control network destruction process have been defined. The solution presented herein is relevant for geodetic practice, providing a standard procedure for defining the time frame and the scope of the control network upgrading. The identified destruction process model optimizes this task assuming critical states expressed by the functionality probability. The applied approach is an example of the reliability theory-based approach typical for engineering. The issue of simulating the destruction process is illustrated with the results of the tests of class 3 control networks conducted in Kielce and Lodz regions in Poland. As a result of the tests, the characteristic properties of the control network destruction process have been identified. It was also shown how the patterns of usability and accuracy of the geodetic control points are relevant on the stage of implementing investment project tasks.

A key element of the system IACS is the verification of the parcel area covered by direct subsidies. Control measurements are made by FOTO method, and in a small part by the direct inspection. Statistical methods are used in estimating the significance of differences. The results of such analysis are correct only when the empirical distributions are consistent with the theoretical ones. The problem of distribution adequacy is presented in the paper on the examples of three objects. The hypotheses about the possibility of using the commonly used distributions, and the appropriateness of the modification of the density curves were verified. By questioning the effectiveness of current methods of analysis, the authors point to the advantages of robust statistics. The cognitive effect of the analysis is to indicate the Laplace distribution as a statistical model of the analyzed differences. Research is concluded by proposal of post-control report that sums up relevant properties of the survey results.