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Abstract:
In the classic Precise Point Positioning (PPP) approach, observations of Global Navigation Satellite System (GNSS) are processed in a GNSS-network and satellite clocks and positions are made available to the user to enable accurate positioning. In the PPP Real-Time-Kinematic (PPP-RTK) approach, satellite phase biases are considered as well so that ambiguity fixing of the network and user ambiguities is possible. In modernized GNSS a vast number of signals and channels exist, providing opportunities and challenges alike. Network processing of uncombined and undifferenced (UDUC) observations, sometimes referred to as the Raw-Method, has gained popularity to handle the increasing number of signals. Processing UDUC observations requires explicit handling of existing rank deficiencies, many of which are eliminated implicitly by the differenced and combined approaches. In the UDUC approach no parameters are pre-eliminated at an observational level and all relevant parameters, such as satellite phase biases must be handled properly.In this contribution a sequential UDUC processing approach is implemented in the form of a Kalman-Filter. Satellite orbits and reference receiver coordinates are fixed to precise apriori values. Satellite clocks, and biases are estimated with a regional GNSS-network. GPS, BeiDou-3, and Galileo Satellites are considered. Different constraints regarding time stabilities of the phase biases are implemented and evaluated. A flexible approach of introducing wide- and narrow-lane ambiguities in sequential processing is presented.The performance of the PPP-RTK enabling products is evaluated with the accuracy of the point position and the time to obtain a fixed solution of a user of the PPP-RTK products.
