Performance evaluation of COATS-based multi-mode and multi-frequency iGNSS-R altimetry

doi:10.11947/j.AGCS.2026.20250218

Abstract

Abstract:

Spaceborne iGNSS-R technology demonstrates promising potential for high spatiotemporal-resolution sea surface change observation, yet related research and performance evaluation remain insufficient. This paper first systematically analyzes waveform characteristics of multi-constellation multi-frequency signals under different modulation schemes, investigates the correlation between waveform quality and environmental parameters, and quantifies signal-to-noise ratio (SNR) variations across different signals. Subsequently, the DER and HALF waveform retracking methods are employed to extract specular reflection delays, while a double delay differential altimetry model calculates sea surface height (SSH), enabling comprehensive evaluation of multi-constellation multi-frequency signal performance in altimetry and ranging. Furthermore, preliminary analysis is conducted on the global average altimetric performance for the COATS mission. Results indicate: BDS B1 and GPS L1/L5 signals exhibit superior SNR and normalized SNR magnitudes；wind speed demonstrates most significant SNR suppression effect within 0~10 m/s range, while increasing incidence angle degrades SNR for high-frequency signals (L1/B1/E1) and GPS L5. GPS L1 (STD 1.46 m), BDS B1 (1.38 m), and Galileo E1 (1.33 m) show significantly better precision compared with corresponding low-frequency signals (L5: 1.84 m, B2: 1.84 m, E5: 1.74 m). The SNR-precision correlation model derived from ranging residual conversion reveals that ranging accuracy improves markedly with SNR enhancement in medium-low SNR regions, while approaching performance bottleneck (1.4~1.5 m) gradually in high SNR regions. Gridded inversion results achieve 99.93%correlation coefficient with DTU 21 model (RMSE 1.156 m). The revisit count-accuracy curve indicates an asymptotic accuracy of 0.60 m when exceeding 2500 revisits.

Key words: iGNSS-R, spaceborne, sea surface height, accuracy evaluation

CLC Number:

P228

Dongliang CHENG, Lingqiu CHEN, Zhiyong HUANG, Shubo QIAO, Dandan WANG, Yaming YAN. Performance evaluation of COATS-based multi-mode and multi-frequency iGNSS-R altimetry[J]. Acta Geodaetica et Cartographica Sinica, 2026, 55(1): 73-89.

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入射角区间/（°）	高频			低频
入射角区间/（°）	GPS	BDS	Galileo	GPS	BDS	Galileo
[0，5）	46 645	117 140	70 423	51 688	108 523	61 755
[5，10）	152 584	332 181	211 687	176 372	309 532	187 398
[10，15）	209 434	541 860	347 660	296 410	508 678	310 369
[15，20）	256 598	734 784	465 352	348 407	690 941	418 939
[20，25）	292 772	867 898	541 226	374 824	814 360	494 755
[25，30）	230 314	749 134	460 987	301 905	690 430	427 891
[30，35）	139 750	458 096	288 224	186 406	390 899	278 385
[35，40）	4	2445	516	37	1011	512
总计	1 328 101	3 803 538	2 386 075	1 736 049	3 514 374	2 180 004

风速区间/（m/s）	高频			低频
风速区间/（m/s）	GPS	BDS	Galileo	GPS	BDS	Galileo
[0，2）	43 154	105 082	67 902	60 493	111 337	72 983
[2，4）	143 058	375 231	246 043	195 489	364 830	243 706
[4，6）	250 835	691 906	440 104	329 828	662 395	415 306
[6，8）	307 878	859 185	551 743	407 868	804 710	506 996
[8，10）	270 152	763 492	480 033	343 943	692 849	429 469
[10，12）	156 080	473 572	285 137	193 421	423 967	246 906
[12，14）	86 302	278 086	166 295	110 219	241 676	141 549
[14，16）	44 138	158 689	92 366	57 985	133 820	77 087
[16，18）	19 468	71 933	39 721	26 506	58 412	32 065
[18，20）	5752	20 125	12 681	8173	15 813	10 484
[20，22）	1066	4803	3244	1775	3418	2796
[22，24）	125	994	780	194	776	657
[24，26）	42	387	25	60	350	0
[26，28）	21	23	0	53	12	0
[28，30）	30	30	0	42	9	0
[30，32）	0	0	1	0	0	0
总计	1 328 101	3 803 538	2 386 075	1 736 049	3 514 374	2 180 004

评估指标	MAE	STD	RMSE	中位数	平均值
L1	1.164	1.463	1.477	－0.194	－0.198
L5	1.447	1.844	1.775	－0.165	－0.082
E1	1.080	1.329	1.375	－0.357	－0.351
E5	1.375	1.746	1.753	－0.188	－0.162
B1	1.111	1.387	1.426	－0.338	－0.334
B2	1.423	1.840	1.854	－0.233	－0.227

评估指标	改正前		改正后
评估指标	中位数	平均值	中位数	平均值
L1	－0.377	－0.428	0.273	0.222
L5	－0.361	－0.337	0.289	0.313
B1	－0.630	－0.622	0.020	0.028
B2	－0.434	－0.431	0.216	0.219
E1	－0.669	－0.670	－0.019	－0.020
E5	－0.364	－0.361	0.286	0.289