Methods of revaluation of former geodetic measurement networks

Abstract

Geodetic field measurements carried out in the past when establishing and updating the land registers were based directly on geodetic measurement networks. The accuracy parameters of these networks are lower compared to modern geodetic measurement networks. Currently, archival materials of the National Geodetic and Cartographic Resources are used in surveying works on real estate. The following paper presents and evaluates three methods of improving the accuracy parameters of former registry and measurement networks. The first method (I) involves transforming the coordinates of former network points into a current coordinate system based on the coordinates of the adjustment points. The second method (II) is based on a strict alignment of a geodetic network together with additional measurement of selected points to strengthen the network. The third method (III) consists of an inventory and measurement of all existing points of former geodetic networks and a strict alignment of the network to determine the coordinates of destroyed points. The effectiveness of the revaluation methods of former networks was assessed on the basis of experimental studies using data from test objects. Satisfactory results of the improvement of accuracy parameters of the network were achieved by the method (I) in those cases in which the ratio of the number of adjustment points to the total number of tested points was approx. 1/3. Similarly, for the method (III), satisfactory results can be achieved if approx. 30% of network points are used as additional control points. However, in the method (II), good results can be achieved if the percentage of searched-out points used as control points is only about 10% of all network points. Examining the complex surveying works (fieldwork and inhouse studies) has shown that both the method (I) and the method (II) of revaluation of geodetic networks have similar efficiency.