GPS precise point positioning (GPS-PPP) technique solutions in GNSS networks

The importance and the usage percentage of PPP technique among GPS/GNSS based positioning techniques have increased rapidly. It becomes a significant alternative to the relative and differential positioning methods for precise point positioning studies with its developing potential. Especially in recent years, this technique provides a wide range application opportunity by the help of high precision ephemerides and clock products, standardized data formats and protocols such as RTCM/NTRIP supported by international organizations i.e. IGS. With this aspect, it becomes effectively used in geodetic studies either in post processing facilities or real time applications. In this study, since this developing process has been considered, it is aimed to test the performance and investigate the accuracy of PPP technique. Different combinations of observations in static and kinematic modes either in real time or post processing have been performed and analyzes have been examined. In the concept of surveying facilities, the test stations have been used as listed; the permanent GPS station located at the roof of the YTU Geomatics Engineering building namely YTUH, ANKR station involved in IGS network located in Ankara and PALA station involved in ISKI-UKBS local network located in Istanbul. Four different investigation scenarios have been performed with related test stations by using different products and software. The first two of these investigations have been performed by using YTUH permanent GPS station. In the first investigation, kinematic PPP solution has been done with approximately 2 hour observation data obtained from YTUH station for real time and post processing analyzes. In the second investigation, repetitive and real time kinematic PPP solutions have been performed for different 100-minute observation periods. In this studies, performance and accuracy of real time kinematic PPP have been analyzed for the 60-90-120 minutes observation periods. The third investigation scenario has been performed at ANKR station by using different software which uses relative and PPP solution algorithms. Here, especially the accuracy of PPP post process analyze solutions have been examined for different observation durations (24, 12, 8, 4,3,2,1 hours) with scientific and internet based software. The forth investigation scenario has been performed with the data obtained from PALA station to compare real-time PPP (RT-PPP), Network-RTK (VRS) and traditional RTK techniques. For Network-RTK VRS solutions, ISKI-UKBS and TUSAGA-Active CORS networks have been used. For traditional-RTK applications, BEYK and ISTN stations have been taken as references and solutions have been performed. In this investigation stage, real time kinematic solutions and analyzes have been realized for three different periods and three different observation durations. The differences obtained from the solutions of 30 and 60 minutes observations have been examined. By this way, performance and accuracy investigation of PPP technique have been performed by using different reference stations, observation durations, equipment and software, data and products. Especially when the geodetic applications have been taken into consideration, it is aimed to give support for regulation facilities to be prepared. The obtained results show that PPP technique may be used for several precise point positioning studies with cm-dm level accuracies.