Recent advances and perspectives in GNSS PPP-RTK

Abstract Precise point positioning-real-time kinematic (PPP-RTK), otherwise known as integer ambiguity resolution-enabled precise pointing positioning, has attracted much attention in recent years and has become state-of-the-art in the global navigation satellite system (GNSS) high-precision positioning community. This work reviews several PPP-RTK methods, outlines a set of PPP-RTK applications, and presents possible future developments. According to the parameterization considered, we clarify the PPP-RTK models into a distinct-clock category and two common-clock categories (common-clock-1 and common-clock-2), in which several ionosphere-free PPP-RTK models can be cast. Compared with the ionosphere-free PPP-RTK model, we emphasize the advantages of the undifferenced and uncombined (UDUC) formulation and recommend the common-clock-1 UDUC PPP-RTK model since it is optimal, flexible, and widely applicable. Based on what kinds of parameters can be estimated by PPP-RTK models, we outline the PPP-RTK applications in several aspects, including position-based applications, time transfer, atmospheric retrieval, and GNSS bias estimation. Despite the huge advances in GNSS PPP-RTK, future research should improve PPP-RTK performances in harsh environments and apply PPP-RTK to mass markets.