Adjustment and transformation strategies of ItalPoS Permanent GNSS Network

Abstract

A private network of 133 GNSS (Global Navigation Satellite Systems) permanent sites, named ItalPoS (Italian Positioning Service) and covering quite uniformly the entire Italian territory, was established since April 2006 by the Italian Division of Leica Geosystems S.p.A. This network involves also several GPS stations of the INGV (Italian National Institute of Geophysics and Volcanology) RING (Real-time Integrated National Gps) network and GPS stations from other public and private administrations. The purpose of ItalPoS network is mainly the GNSS data distribution in terms of real time corrections and RINEX (Receiver INdependent EXchange) files for the post-processing. In order to compute and distribute to private and scientific users a set of adjusted coordinates of the ItalPoS network in the IGS05 and ETRF89-ETRF2000 (European Terrestrial Reference Frame) reference frames, a dataset of RINEX of 133 GPS permanent sites was created and processed, using the distributed sessions approach, by means of Gamit/Globk 10.3 GPS data processor, using also some SOPAC (Scripps Orbit and Permanent Array Center) and EUREF (Reference Frame Sub Commission for Europe) solutions to improve the reference frame definition and the internal constraint. All the strategies adopted to estimate coordinates and velocities of the ItalPoS Network in IGS05 will be described together with the investigated approaches to provide coordinates in ETRF89-ETRF2000 reference frames: in this case both Helmert and Boucher-Altamimi transformations were taken into account, the whole Italian territory was divided into three parts in order to optimize transformation residuals. Particular attention was paid to transition areas.