Experimental evaluation of the accuracy parameters of former surveying networks

Surveying field measurements performed during the development and updating of land registry were based directly on measuring networks. Accuracy parameters of these networks are lower in comparison with modern measurement networks. The main reasons for the lower accuracy relate mainly to the lower precision of measurements, two orders of network and approximate techniques for determining the coordinates of the points of these networks. Currently, archival materials of the State Geodetic and Cartographic Resource are used during surveying of real estate (division, separation, modernization of land registry). The paper presents the results of experimental evaluation of the accuracy parameters of former networks. The purpose of the performed evaluation to was to analyze the possibilities of use archival materials of the State Geodetic and Cartographic Resource during surveying works related to real estate. The study was carried out on the basis of three test objects located in the Małopolskie voivodship. Points of the analyzed networks found on the ground were measured (approx. 34% of all points), and then their coordinates were determined. The representative research sample was constituted by sets of deviations Z - the length of the displacement vector of the point in the research sample in relation to its position considered as error free. The basic estimator of the accuracy of analyzed networks was the root mean square error RMSE. This estimator was determined on the basis of a vector Z* originating from the set, from which the outlying observations were removed. Values of calculated RMSE show, that for the analyz ed objects the required accuracy is met by no more than 16% of the points of the networks (RMSE ≤ 0.20 m). Therefore, it may be concluded, that for more than 80% of the border points the average position errors exceed the threshold size: 0.30 m relative to the 1st class geodetic network. Hence the conclusion that during surveying real estate, archival materials of the State Geodetic and Cartographic Resource should be used in a limited scope.