MEASUREMENT, cilt.145, ss.361-369, 2019 (SCI İndekslerine Giren Dergi)
In recent years, the precise products generated by the International GNSS Service (IGS) as a part of the Multi-GNSS Experiment (MGEX) project have been increasingly used for multi-GNSS applications. Nowadays, six IGS Analysis Centers (ACs) have been providing GNSS products with different features. However, there is still neither a combined solution nor a standard accuracy definition for MGEX products, unlike the standard IGS products. For the GNSS techniques that are directly dependent on precise products, such as Precise Point Positioning (PPP), the quality of these products is a very crucial point in positioning performance. In this context, this study aims to investigate the impact of MGEX products provided by different IGS ACs on post-processing PPP performance in terms of accuracy, availability, and consistency. For this purpose, an experimental test was performed including all possible multi-GNSS combinations of GPS, GLONASS, Galileo, and BeiDou. 24-hour observation datasets collected at ten IGS stations during the 1-month period of May 1-31 were processed with twelve PPP modes using all available precise products. As a first step, an analysis of product availability was carried out for the related MGEX precise products within the test period to be able to assess the impact of the availability on the test results. PPPH software was used to perform the test and the results were statistically assessed as regards positioning error, RMS error and convergence time. The results indicate that the PPP performance may considerably differ depending on the precise products utilized in the PPP process. For the test period, PPP solutions utilizing the precise products generated by GFZ (GeoForschungsZentrum Potsdam) and WU (Wuhan University) agencies have relatively better positioning performance for nearly all processing modes compared to other solutions. The quality and availability of precise products are significant factors which lay behind the better PPP performance. On the other hand, while the integration of two or more systems significantly strength the PPP performance, GPS is still the dominant system for PPP and the solutions that do not include GPS constellation have very poor performance. The results also show that MGEX products have different impacts on the PPP performance as varying with the constellation involved in PPP solution and the geographical location of the station. (C) 2019 Elsevier Ltd. All rights reserved.