Abstract
In the traditional raw Doppler (RD) velocity estimation method, the positioning error of the pseudorange-based global navigation satellite system (GNSS) single point positioning (SPP) solution affects the accuracy of the velocity estimation through the station-satellite unit cosine vector. To eliminate the effect of positioning errors, this paper proposes a carrier-phase-based second generation of the BeiDou navigation satellite system (BDS-2) precise point positioning (PPP) RD velocity estimation method. Compared with the SPP positioning accuracy of tens of meters, the BDS-2 kinematic PPP positioning accuracy is significantly improved to the dm level. In order to verify the reliability and applicability of the developed method, three dedicated tests, the vehicle-borne, ship-borne and air-borne platforms, were conducted. In the vehicle-borne experiment, the GNSS and inertial navigation system (INS)-integrated velocity solution was chosen as the reference. The velocity accuracy of the BDS-2 PPP RD method was better than that of SPP RD by 28.4%, 27.1% and 26.1% in the east, north and up directions, respectively. In the ship-borne and air-borne experiments, the BDS-2 PPP RD velocity accuracy was improved by 17.4%, 21.4%, 17.8%, and 38.1%, 17.6%, 17.5% in the same three directions, respectively, compared with the BDS-2 SPP RD solutions. The reference in these two tests is the real-time kinematic (RTK) Position Derivation (PD)-based velocity.
Highlights
The position derivation (PD), raw Doppler (RD), carrier-phase-derived Doppler (DD) and time-differenced carrier phase (TDCP) methods are four major velocity estimation approaches for satellite-based applications
The Position Derivation (PD) velocity estimation method makes use of the first-order derivation of consecutive positions; the RD velocity estimation method refers to the raw Doppler measurements for velocity determination; the DD method utilizes the Doppler measurements derived from carrier phase observations, rather than the Raw Doppler measurement in the RD method, at two consecutive epochs to calculate the velocity; and the TDCP method takes advantage of the pseudorange and carrier phase observations at two consecutive epochs to determine the velocity
Among the four velocity estimation methods, the RD method is more suitable for kinematic velocity estimation applications with complex movements
Summary
The position derivation (PD), raw Doppler (RD), carrier-phase-derived Doppler (DD) and time-differenced carrier phase (TDCP) methods are four major velocity estimation approaches for satellite-based applications. The RMS statistics of the RD and DD methods with respect to the inertial navigation system (INS) velocity solution were 13.9, 9.9, 6.8 cm/s and 14.4, 10.7, 8.1 cm/s, respectively, for the three directions. Liu et al [5] compared the BDS SPP RD and DD velocity estimation methods Their RMS values in the static experiment were 1.5, 2.0, 4.7 cm/s and 1.8, 2.6, 6.3 mm/s for the RD and DD method, respectively. Applied this method to GPS/INS integrated navigation, which improved the velocity estimation accuracy in the integrated system. Only the RD method estimates the instantaneous velocity of the moving object based on Doppler observations at the instantaneous epoch, is more suitable for real-time navigation applications with complex motions
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