Control network analysis of the dam "Wióry"

The obtained results of the test measurements in the control network of the dam Wióry show that combined usage of length measurements and GPS observations enables to obtain high accuracy and reliability in defining point coordinates. The real determination accuracy of checkpoint displacements in this type of networks is at the level of (plus minus) 2-3mm. However, it should be added that in small networks covering an area up to 1 km in radius, classical measurements (most of all, length measurements) enable to obtain higher accuracies in determining point coordinates, obviously on condition that the net structure is well-designed and length measurement is possible. Having analyzed the obtained results, one can also formulate the following conclusions: - the assumed structure of a modified test network shows effective accuracy both for EDM measurements and GPS observations, - satellite measurements enable combined and direct observation of points between which there is no sight line. It is especially important in the case of reference points which are usually located around the monitored object, and it is rarely possible to link them by means of classical measurements; - GPS measurements make it possible to check the monitored network independently, at least limiting the incidence of major and systematic errors in processing the results and defining displacement values; so GPS observations may, in the case of small control networks, be treated as control measurements made periodically (e.g. every year); - accuracy assessment made for TDA5005 tachymeter observations even in the case of considerable target inclinations, made by means of standard reflectors, attested reflexive foil and CCR fulfills monitoring requirements of specific point (targets), enabling to obtain an accuracy of the (plus minus) 0.5 mm range in relation to reference points; - linear measurements in the test network of Wiory, made by means of a TDA5005 tachymeter and high precision reflectors can be accomplished within 2-3 days.