## 1 Introduction  
In recent years, the world of satellite-based positioning has experienced dramatic changes. A few decades ago, it was necessary to make carrier-phase based measurements with at least two geodetic-types of Global Navigation Satellite System (GNSS) receivers (one as a rover and at least one for the base) for achieving high accuracy positioning. However, nowadays, new methods and techniques using a single GNSS receiver have been developed to make it possible to determine the positions accurately without using data from any reference station. Precise Point Positioning (PPP), as one of the most common and successfully used methods, allows positioning with centimeter to decimeter (dm) level accuracy in static and kinematic applications by using a single GNSS receiver after convergence. Convergence (initialization time) is inevitable due to the phase ambiguity solution required to achieve a highly accurate position. However, convergence is a problem only in real-time PPP applications or where only one-way (forward or backward) post-processed PPP is applied. In the PPP technique, point positioning can be realized by using precise satellite position and clock data obtained from mainly International GNSS Service (IGS), Analysis Centers (ACs), and other organizations. As an alternative to relative GNSS positioning, PPP is widely used in many different scientific and practical applications that require cm-level accuracy. The attainable PPP accuracy meets the demands of various surveying applications that require high precision positioning [1; 2; 3; 4]. This technique has drawn attention to the GNSS community because it is practical and does not require any base station data; hence, it is cost-effective with simple field operations in accurate positioning. The accuracy levels, obtained from this technique, vary depending on a number of factors including accuracy of the precise products, used constellations, single or multi-frequency data used in the process, satellite geometry, receiver environment conditions, atmospheric conditions, proper modelling of the additional corrections, processing strategies, and so on. In 1997, the PPP technique was first applied using only GPS (Global Positioning System) observations; however, with the advent of precise satellite orbit and clock corrections for other satellite systems, besides the GPS-only, PPP using multi-constellation GNSS (or multi-GNSS) data has emerged [5]. In consequence of this progress, positioning accuracy has significantly improved, convergence time shortened since the measurement redundancy increased and satellite geometry enhanced when the multiple GNSS constellation was employed. This advantage is more evident especially in areas having blockages or limitations receiving GNSS signals [5]. Regarding the reported progress in GNSS PPP with multiple constellations, in this case study, the aim is to investigate the effect of different Multi-GNSS Experiment (MGEX) precise products on kinematic multi-GNSS PPP accuracy performance under different satellite constellation combinations in a dynamic environment. In all kinematic PPP processing in this study, classical ionosphere-free (IF) linear combination (L3) based float ambiguity solution was used. According to nine different solutions in the study, it is clearly seen that the obtained cm level of kinematic PPP accuracy is affected by not only the observed GNSS constellations but it is also highly dependent on the chosen precise orbit and satellite clock products in the solution. IGS MGEX ACs use different datasets, different strategies, and different software, while producing precise products; however, because of contained systematic errors, different products give different positioning accuracy. However, the accuracy of the precise orbit and clock information of different satellite systems in a product could be different.