Phase clock/bias estimation for GNSS all-frequency undifferenced ambiguity resolution

doi:10.11947/j.AGCS.2024.20230060

Abstract

Abstract:

Undifferenced ambiguity resolution is a crucial technology for GNSS precision point positioning (PPP). The conventional PPP method typically uses ionosphere-free combination observations on the specific baseline frequencies (e.g., GPS L1/L2). Therefore, the satellite clock and phase bias products required for ambiguity resolution (AR) are bounded to these specified observation models and signal frequencies, which significantly limits the user's choice. To meet the user's demand for high-precision positioning with free choice of signal frequencies, this paper proposes an estimation method of “all-frequency phase clock/bias”, which employs the undifferenced integer ambiguity constraints on the network processing to estimate phase clock and observable-specific signal bias (OSB) products. While ensuring their consistency with the datum of IGS (International GNSS Service) legacy clock and bias, these products enable the PPP ambiguity resolution applicable to arbitrary observation model and frequency choices. Both a 31-day test on 197 IGS MGEX (multi-GNSS experiment) stations and a kinematic test on car-borne data demonstrate that the GPS/Galileo/BDS all-frequency phase clock/bias product proposed by this paper maintains relatively consistent ambiguity resolution efficiency and static/kinematic positioning accuracy over any frequency combination in PPP-AR. In particular, we emphasize that the undifferenced integer ambiguity constraint applied to the network processing plays a vital role in guaranteeing the strict coupling of the satellite phase clock/bias products, which is essential to ensure the capability of all-frequency undifferenced ambiguity resolution. The all-frequency phase clock/bias products from Wuhan University (ftp://igs.gnsswhu.cn/pub/whu/phasebias/) have been released since 2023 as a rapid routine service.

Key words: all-frequency PPP-AR, undifferenced ambiguity resolution, phase clock, phase bias, multi-GNSS

CLC Number:

P228

Jianghui GENG, Jihang LIN, Qiyuan ZHANG, Qiang WEN, Jing ZENG, Biao JIN. Phase clock/bias estimation for GNSS all-frequency undifferenced ambiguity resolution[J]. Acta Geodaetica et Cartographica Sinica, 2024, 53(12): 2254-2267.

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可估参数	表达式	估计方法
名义几何项		逐历元参数
接收机钟差		逐历元参数
卫星钟差		逐历元参数
电离层延迟		逐历元参数
接收机伪距IFB		常数
卫星伪距IFB		常数
相位模糊度		常数
接收机相位偏差		常数
卫星相位偏差		常数
卫星相位IFCB		分段线性函数

波段	频率/MHz	信号名称
波段	频率/MHz	GPS	Galileo	BDS-2	BDS-3
上行波段	1 575.420	L1^*	E1^*	—	B1C
上行波段	1 561.098	—	—	B1I^*	B1I^*
	1 278.750	—	E6	—	—
	1 268.520	—	—	B3I^*	B3I^*
下行波段	1 227.600	L2^*	—	—	—
下行波段	1 207.140	—	E5b	B2I	B2b
	1 191.795	—	E5	—	—
	1 176.450	L5	E5a^*	—	B2a

频率组合	平均宽巷固定率/（%）	平均窄巷固定率/（%）	卫星数量	测站数量
L1+L2	91.36	95.97	31	197
L1+L5	81.94	93.16	18	197
E1+E5a	97.90	96.75	23	196
E1+E6	96.30	94.91	23	194
E1+E5b	98.00	96.33	23	197
E1+E5	98.77	96.40	23	194
BDS-2 B1I+B3I	85.98	82.74	10	126
BDS-2 B1I+B2I	79.36	84.20	10	127
BDS-3 B1I+B3I	92.80	92.42	27	197
B1I+B2a	88.25	94.21	27	197
B1I+B2b	85.42	94.25	27	126
B1C+B3I	94.90	92.48	27	196
B1C+B2a	94.07	92.21	27	196
B1C+B2b	89.98	94.01	27	126

频率组合	浮点解RMSE			固定解RMSE
频率组合	东	北	高	东	北	高
L1+L2	3.0	1.7	4.9	1.7	1.6	4.3
L1+L5	4.7	2.5	7.9	2.8	2.4	7.8
E1+E5a	3.1	2.1	6.9	2.1	2.1	6.2
E1+E6	3.8	2.8	8.6	2.6	2.6	7.8
E1+E5b	3.1	2.3	6.0	2.0	2.2	5.4
E1+E5	3.2	2.6	6.8	2.1	2.6	6.2
B1I+B3I	4.3	3.5	9.5	3.2	3.3	8.8
B1I+B2I/b	4.8	4.1	8.4	3.3	3.7	7.5
B1I+B2a	4.0	3.6	8.4	3.1	3.5	8.2
B1C+B3I	3.7	3.2	8.3	2.7	2.9	7.6
B1C+B2b	3.3	2.5	6.7	2.3	2.4	6.2
B1C+B2a	3.6	2.4	7.8	2.6	2.4	7.4

频率组合	浮点解STD			固定解STD
频率组合	东	北	高	东	北	高
L1+L2	9.0	8.4	21.8	6.3	7.4	19.9
L1+L5	36.5	27.1	57.8	31.9	25.1	56.2
E1+E5a	11.2	9.4	25.8	7.7	7.9	22.7
E1+E6	13.4	11.1	29.7	9.2	9.5	26.5
E1+E5b	11.7	9.8	26.7	8.0	8.3	23.4
E1+E5	11.3	9.4	26.1	7.7	8.0	23.0
B1I+B3I	12.9	10.3	27.5	10.2	9.4	26.3
B1I+B2I/b	11.1	8.8	24.0	8.8	8.0	23.2
B1I+B2a	12.9	10.3	27.5	10.2	9.4	26.3
B1C+B3I	11.1	8.8	24.0	8.8	8.0	23.2
B1C+B2b	11.8	9.0	24.9	9.0	8.2	23.7
B1C+B2a	12.4	9.7	26.3	9.7	8.8	25.2