Abstract
The emergence of dual frequency global navigation satellite system (GNSS) chip actively promotes the progress of precise point positioning (PPP) technology in Android smartphones. However, some characteristics of GNSS signals on current smartphones still adversely affect the positioning accuracy of multi-GNSS PPP. In order to reduce the adverse effects on positioning, this paper takes Huawei Mate30 as the experimental object and presents the analysis of multi-GNSS observations from the aspects of carrier-to-noise ratio, cycle slip, gradual accumulation of phase error, and pseudorange residual. Accordingly, we establish a multi-GNSS PPP mathematical model that is more suitable for GNSS observations from a smartphone. The stochastic model is composed of GNSS step function variances depending on carrier-to-noise ratio, and the robust Kalman filter is applied to parameter estimation. The multi-GNSS experimental results show that the proposed PPP method can significantly reduce the effect of poor satellite signal quality on positioning accuracy. Compared with the conventional PPP model, the root mean square (RMS) of GPS/BeiDou (BDS)/GLONASS static PPP horizontal and vertical errors in the initial 10 min decreased by 23.71% and 62.06%, respectively, and the horizontal positioning accuracy reached 10 cm within 100 min. Meanwhile, the kinematic PPP maximum three-dimensional positioning error of GPS/BDS/GLONASS decreased from 16.543 to 10.317 m.
Highlights
At the May 2016 Google I/O developer conference, it was announced that general developers would be provided with the raw global navigation satellite system (GNSS) measurements of smartphones and tablets with Android N (“Nougat” = version 7) version operating system [1], which enables the raw GNSS observations of smartphone to output directly in RENIX format with application (APP)
The rate of GNSS carrier phase cycle slip on the Huawei Mate30 is inversely related to the carrier-to-noise ratio, and the most cycle slips are largely concentrated in the carrier-to-noise ratio below 30 dB-Hz
This means that the conventional stochastic model depending on elevation is difficult to accurately reflect the GNSS observation quality of the smartphone
Summary
The GPS/Galileo pseudorange and carrier phase observations L1/L5 and E1/E5 of Xiaomi Mi 8 were used in the ionosphere-free combined PPP mathematical model [11], and the experimental results showed that the dual frequency GNSS smartphone is capable of achieving decimeter-level positioning accuracy. Wu et al [12] recorded that Xiaomi Mi 8 received more than four satellites with L5/E5 band for about 13 h in 24-h collection This makes it difficult to meet the requirement of dual frequency PPP based on GPS/Galileo for a smartphone during the whole day. It intermittently puts the receiving device into a sleep state, especially in static mode the sleep period can be set to the maximum [15] This function will seriously affect the reception of GNSS carrier phase observations.
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