# The Implementation of Precise Point Positioning (PPP): A Comprehensive Review
###### Abstract  
High-precision positioning from Global Navigation Satellite Systems (GNSS) has garnered increased interest due to growing demand in various applications, like autonomous car navigation and precision agriculture. Precise Point Positioning (PPP) offers a distinct advantage over differential techniques by enabling precise position determination of a GNSS over receiver through the use of external corrections sourced from either the Internet or dedicated correction satellites. However, PPP's implementation has been challenging due to the need to mitigate numerous GNSS error sources, many of which are eliminated in differential techniques such as Real-Time Kinematics (RTK) or overlooked in Standard Point Positioning (SPP). This paper extensively reviews PPP's error sources, such as ionospheric delays, tropospheric delays, satellite orbit and clock errors, phase and code biases, and site displacement effects. Additionally, this article examines various PPP models and correction sources that can be employed to address these errors. A detailed discussion is provided on implementing the standard dual-frequency (DF)-PPP to achieve centimeter- or millimeter-level positioning accuracy. This paper includes experimental examples of PPP implementation results using static data from the International GNSS Service (IGS) station network and a kinematic road test based on the actual trajectory to showcase DF-PPP development for practical applications. By providing a fusion of theoretical insights with practical demonstrations, this comprehensive review offers readers a pragmatic perspective on the evolving field of Precise Point Positioning. GNSS; precise positioning; PPP; PPP errors; PPP corrections; IGS 22 August 202316 October 20232 October 20232 October 20232 October 20232 October 202  
positioned reference stations [5]. The core principle of DGNSS is that when the baseline length--defined as the distance between the rover receiver and the reference station--is adequately short (e.g., less than 40 km), certain errors, including atmospheric delays, satellite orbit, and satellite clock errors, become spatially correlated. These correlated errors can then be effectively eliminated using differencing techniques. The Real-Time Kinematics (RTK) is a carrier-phase-based DGNSS technology that provides centimeter-level real-time positioning accuracy [4]. Nonetheless, the overheads associated with reference station setup and the inherent baseline length constraints underscore the limitations of DGNSS. Introduced in 1997, Precise Point Positioning (PPP) is a technique that facilitates the precise and accurate estimation of a user's global position using a single GNSS receiver [6]. PPP determines the absolute receiver position, relying exclusively on the rover receiver's GNSS measurements and a global spectrum of precision correction data. Since PPP must consider all error sources neglected in DGNSS, its pivotal challenge remains the convergence time required for resolving IA to achieve centimeter-level precision [7]. However, the ability of PPP to provide a globally applicable solution via a single receiver has gained significant interest within the research community, leading to ongoing efforts to overcome its limitations [8]. PPP can be applied in many aspects of our daily life. For example, in [9], PPP was integrated with high-end inertial sensors for lane-level autonomous land vehicle navigation on highways. Other papers investigated the integration of PPP with low-cost inertial sensors for land vehicle navigation in GNSS-challenging environments [10; 11]. PPP was also applied for precision agriculture [12] and atmospheric monitoring [13]. In [14], PPP with the BeilDou B2b products was used for earthquake monitoring. Several open-source software tools can be used for PPP, such as RTKLIB [15], GAMP [16], PPPH [17], PPPLib [18], raPPPiot [19], and PPP-ARISEN [20].