An Enhanced Real-Time Regional Ionospheric Model Using IGS Real-Time Service (IGS-RTS) Products Mohamed Abdelazeem 1,2 , Rahmi N. Çelik 1 and Ahmed El-Rabbany 2 1 (Geomatics Engineering Department, Istanbul Technical University, Turkey) 2 (Civil Engineering Department, Ryerson University, Canada) (E-mail: moh.azm84@gmail.com) Recently, the International Global Navigation Satellite System (GNSS) Service (IGS) has launched the Real-Time Service (IGS-RTS). The RTS products enable real-time precise positioning applications. For single-frequency Real-Time Precise Point Positioning (RT-PPP), ionospheric delay mitigation is a major challenge. To overcome this challenge, we developed a Real-Time Regional Ionospheric Model (RT-RIM) over Europe using the RTS satellite orbits and clock products. The model has spatial and temporal resolution of 1° × 1° and 15 minutes, re- spectively. Global Positioning System (GPS) observations from 60 IGS and EUREF reference stations are processed using the Bernese 5·2 PPP module in order to extract the Real-Time Vertical Electron Content (RT-VTEC). The PPP convergence time and positioning accuracy using the RTS products is estimated and compared with dual frequency PPP and single-frequency PPP obtained through the combined rapid IGS Global Ionospheric Maps (IGS-GIM) over three consecutive days under high solar activity and one of them under active geomagnetic activity. The results show that the proposed model improves PPP accuracy and convergence time under the mid-latitude region about 40%, 55% and 40% for the horizontal, height and three-dimensional (3D) components respectively in comparison with the IGS-GIM. KEYWORDS 1. IGS-RTS Products. 2. PPP. 3. Ionospheric model. Submitted: 19 March 2015. Accepted: 12 September 2015. First published online: 6 October 2015. 1. INTRODUCTION. The estimation of the ionosphere Total Electron Content (TEC) and its change is an important issue for precise positioning and space weather applications. Ionospheric delay is the dominant error source in single- frequency Precise Point Positioning (PPP). Therefore, mitigation of ionospheric delay in real-time is a major challenge for single-frequency PPP users. In order to provide real-time PPP users with more precise products, the International Global Navigation Satellite System (GNSS) Service (IGS) has launched its Real-Time Service (IGS-RTS). The RTS has become available through the collaboration of THE JOURNAL OF NAVIGATION (2016), 69, 521–530. © The Royal Institute of Navigation 2015 doi:10.1017/S0373463315000740 https://doi.org/10.1017/S0373463315000740 Published online by Cambridge University Press