Conformal and empirical transformation between the PL-ETRF89 and PL-ETRF2000 reference frames using the new adjustment of the former Polish I class triangulation network

: The European reference frame ETRF2000 was introduced on the territory of Poland on 1 July 2013, named PL-ETRF2000, as a result of the appropriate measurement campaign 2008-2011. The new PL-ETRF2000 reference frame has replaced the previously used PL-ETRF89 frame, which had more than 10 years of history in Poland until 2013, implemented in almost all geodetic and cartographic “products”, in geodetic networks, economic map systems and databases. The relationship of the new reference frame with the previously used PL-ETRF89 frame has become an important practical issue. Currently, all position services of the ASG-EUPOS (Active Geodetic Network – EUPOS) system use only the PL-ETRF2000 reference frame, which also results from the relevant legal and technical regulations. The relationships between the frames was considered in two aspects: “theoretical”, expressed by conformal (Helmert, 7-parameter) transformation, and “empirical”, based on an interpolation grid that allows to take into account local distortions of the PL-ETRF89 frame. The estimation of the parameters of the conformal transformation model was based on 330 points of the POLREF network, while to create an interpolation grid approximately 6500 points of the old triangulation network were additionally used, after new adjustment in PL-ETRF200 reference frame. Basic algorithms for the transformation between two frames and mapping systems are implemented in the