Preliminary verification and analysis of positioning accuracy of the satellite laser altimetry products

doi:10.11947/j.AGCS.2025.20240132

Abstract

Abstract:

Effective evaluation of the geometric positioning accuracy of satellite laser altimetry products is the basis and prerequisite for safeguarding their subsequent applications. After the satellite is in orbit, the laser optical axis pointing and platform stability will change over time, leading to deviations in the positioning position of the laser spot on the ground. Aiming at the working mode of the laser altimetry system of the Gou Mang satellite, this paper first determines the spot position on the laser footprint camera and the optical axis pointing, and proposes an ellipse fitting method based on the maximum gradient of spot energy (MG-EFM) to analyze the stability of the laser emission pointing after the satellite is in orbit. Then, the position of the laser footprint point on the ground is calibrated using high-precision terrain data to analyze the geometric positioning accuracy of the laser. The experimental results show that: ①The MG-EFM method extracts the center of the laser spot with an accuracy of better than 0.1 pixel, which can be used for monitoring the stability of the laser optical axis pointing and effectively identifying the drift error of the laser optical axis in the short term. ②The laser geometric positioning of the Gou Mang in the Northeast Tiger and Leopard National Park area is relatively stable. However, it has been found that with variations in the satellite measurement environment and observation time, the laser spot positioning exhibits time-varying error distribution characteristics, especially there is an inconsistency of about 10 m in the ground positioning of the laser spots observed during day and night. To meet the operational application requirements of satellite laser altimetry products, ground control data should be added to enhance the geometric stability of the products.

Key words: laser altimetry, footprint camera, positioning accuracy analysis, stability monitoring, Gou Mang, terrestrial ecosystem carbon inventory satellite

CLC Number:

P236

Qifan YU, Anmin FU, Shaoning LI, Xiaotong LIU. Preliminary verification and analysis of positioning accuracy of the satellite laser altimetry products[J]. Acta Geodaetica et Cartographica Sinica, 2025, 54(2): 321-333.

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指标	设计值
轨道高度/km	506
激光波束数	5
波长/nm	1064
发射频率/Hz	40
采样频率/GHz	1.2
光斑直径/m	25
足印影像分辨率/m	8

方法	平均误差		标准差		均方根误差
方法	X	Y	X	Y	X	Y	整体
GFM	0.137	0.088	0.165	0.217	0.215	0.234	0.318
GCM	0.057	-0.035	0.035	0.193	0.067	0.196	0.207
MG-EFM	-0.003	0.001	0.052	0.068	0.053	0.068	0.086

时段	波束	极差/像素		标准差/像素
时段	波束	X	Y	X	Y	整体
白天	1	0.346	0.286	0.132	0.094	0.162
	2	0.227	0.742	0.076	0.243	0.255
	3	1.428	0.393	0.507	0.142	0.527
	4	0.547	0.730	0.197	0.263	0.329
	5	0.939	0.748	0.332	0.281	0.435
夜间	1	0.406	0.205	0.137	0.067	0.153
	2	0.377	0.732	0.123	0.275	0.301
	3	1.168	0.358	0.373	0.129	0.395
	4	0.363	0.610	0.155	0.243	0.288
	5	0.904	0.708	0.343	0.270	0.437

时段	激光波束	轨道数	激光点数	平面定位精度/m			高程精度（均方根误差）/m
时段	激光波束	轨道数	激光点数	平均误差	标准差	中误差	校正前	校正后
白天	波束1	21	970	14.28	2.79	14.54	2.45	1.33
	波束2	21	1122	17.21	3.18	17.49	2.94	1.38
	波束3	21	1183	14.31	2.53	14.52	2.87	1.31
	波束4	21	1122	13.47	3.14	13.81	2.54	1.48
	波束5	21	1061	12.86	2.44	13.08	2.78	1.61
	合计	105	5458	14.43	3.16	14.76	2.73	1.42
夜间	波束1	6	371	23.81	3.32	24.00	3.68	1.53
	波束2	6	455	24.74	4.18	25.03	3.87	1.39
	波束3	6	500	22.02	4.74	22.44	3.87	1.40
	波束4	6	423	22.37	4.76	22.79	3.19	1.45
	波束5	6	424	22.69	3.91	22.97	3.58	1.31
	合计	30	2173	23.12	4.05	23.46	3.66	1.41

对比标识号	激光波束	白天		夜间
对比标识号	激光波束	南北偏移/m	东西偏移/m	南北偏移/m	东西偏移/m
1	波束1	-1.56	13.26	19.20	13.26
2	波束2	-2.52	13.86	20.64	12.24
3	波束3	-1.32	17.82	17.52	8.94
4	波束4	1.50	14.64	16.86	12.84
5	波束5	2.04	13.50	19.44	12.12
6	波束1	-0.12	8.82	22.44	9.48
7	波束2	-4.92	7.32	26.10	10.20
8	波束3	-3.72	12.78	24.12	6.54
9	波束4	1.08	12.42	21.60	11.64
10	波束5	2.28	10.20	22.67	12.00
11	波束1	-3.42	13.74	26.70	8.58
12	波束2	-2.28	11.46	25.20	7.80
13	波束3	-1.68	15.42	26.40	4.50
14	波束4	-1.26	12.90	20.40	9.48
15	波束5	2.21	11.46	22.26	11.10
平均值		-0.91	12.64	22.10	10.05
标准差		2.32	2.59	3.15	2.49