A First Estimate of the Transformation Between the Global IGS and the Italian ETRF89-IGM95 Reference Frames for the Italian Peninsula

Abstract

Typically, the local permanent GNSS networks for positioning services are adjusted in the IGS realization of ITRS (at the present, IGb00): therefore, the positions estimated by their users are expressed in this reference frame; however, typically in surveys finalized to cartographic purposes within Europe, ETRS89 coordinates may be required. A time series of ETRS89 realizations is published by IERS and EPN: the present is ETRF2000; in Italy the official cartographic realization is materialized by the IGM95 network, originally constituted of about 1250 markers, surveyed in the ‘90 and adjusted in ETRF89. At the present epoch, the planimetric differences between current realizations of ITRS and ETRS89 are of some decimeters; due to the survey accuracy and the elapsed time, IGM95 exhibits both correlated, from the national to the local scale, deformations and sparse errors, up to one dm. The analysis of the relationships between the above reference frames is strategic for GNSS positioning services, in order to provide coordinates in the reference frame required by the users. At a national scale, the published IGb00 and ETRF2000 coordinates of the Italian permanent stations have been used to estimate a similarity transformation; at a local scale, for the Piemonte, and Lombardia regions, where data were available, the estimated IGb00 and the published ETRF89 coordinates of the IGM95 markers have been used to validate the transformation and to investigate in more detail the local deformations. The paper discusses the analysis approach, the developed software and the first results.