An Assessment of the Precise Products on Static Precise Point Positioning using Multi-Constellation GNSS
Jareer Mohammed, College of Engineering, University of Wasit, Iraq; Terry Moore, Chris Hill, Richard M. Bingley, University of Nottingham, UK
Alternate Number 2
Precise point positioning (PPP) is highly dependent on the precise ephemerides and satellite clock products that are used. Different ephemeris and clock products are available from a variety of different organisations. The aim of this paper is to assess the achievable accuracy and precision when using different precise ephemerides from three analysis centres EMX, ESA and GFZ, using GPS only (PPP GPS) GLONASS only (PPP GLO) and GPS plus GLONASS (PPP GPS+GLO), for static positioning. It will be shown that the precise products are affected by the reference station time-base that is propagated to all the estimated satellite clocks. This needs to be handled with an appropriate variation in the estimated receiver clock, in the PPP processing, to overcome the combined biases in the estimated satellite clock. It will also be shown that the precise coordinates of the satellites differ between the analysis centres, and this affects the PPP position estimation at the millimetre level. However, and from a PPP point of view, all those products will be shown to result in the same level of precision for all coordinate components and are equivalent to the horizontal precision from a Global Double Difference (GDD) solution. For the horizontal PPP component, the level of agreement is at the millimetre level. There is a notable, but small, bias in the north coordinate components of the PPP solutions from the corresponding north component of the GDD solutions. This difference is due to the different strategy adopted for the GDD and PPP solutions, with PPP being more affected by the constellation type. The precision of the determined heights will be shown to be almost the same for all PPP scenarios with all three products. Finally, it will be concluded that accuracy of the height component is system dependent and related to the behaviour of antenna phase centre with the different constellation type.