Geometric positioning integrating optical satellite stereo imagery and a global database of ICESat-2 laser control points: A framework and key technologies

Figures & data

Table 1. Basic parameters of several laser altimeter satellites used for stereo mapping.

Satellite	ICESat	ICESat-2	ZY-3 03	GF-7
Satellite Type	specialized	specialized	stereo mapping	stereo mapping
Launch Country	the US	the US	China	China
Launch Time	2003	2018	2016	2019
Spot Diameter (m)	70	~17	75	~15 (Tang et al. 2020)
Beam Spacing (Across Track) (m)	one beam	Maximum: 3300 Minimum: 90	one beam	12,500
Beam Spacing (Along Track) (m)	170	0.7	3500	2330
Elevation Accuracy (m)	0.15	0.1	1.0	0.1 (plain terrain) (Tang et al. 2020)
Data Availability	freely available	freely available	unavailable	unavailable
Observation Missions	observation of ice, cloud, land elevation, etc.	observation of ice, cloud, land elevation, etc.	acquisition of global elevation control points and stereo mapping	acquisition of global elevation control points and stereo mapping

Figure 1. Framework of the geometric positioning model integrating OSSI and spaceborne laser altimeter data.

Figure 2. Acquisition and management of the global laser control points (LCPs).

Table 2. Classification rules of LCPs by elevation accuracy.

Elevation difference $\mathrm{\Delta }\mathrm{H}$ with reference DEM (Ref_Accur) (unit: meter)	$\mathrm{\Delta }\mathrm{H}$≤0.1	0.1<$\mathrm{\Delta }\mathrm{H}$≤0.2	0.2<$\mathrm{\Delta }\mathrm{H}$≤0.5	0.5<$\mathrm{\Delta }\mathrm{H}$≤1	1<$\mathrm{\Delta }\mathrm{H}$≤3	$\mathrm{\Delta }\mathrm{H}$>3
Elevation accuracy level (Lv_Accur) (unit: meter)	1	2	3	4	5	6

Table 3. Evaluation accuracy of laser control points with different elevation accuracy levels.

Elevation accuracy level of LCP (Lv_Accur)	Elevation mean error (m)	Root mean square error (m)	Proportion in total data
1	−0.09	0.51	4.97%
2	−0.10	0.52	4.81%
3	−0.11	0.54	15.43%
4	−0.11	0.56	23.81%
5	−0.14	0.70	40.47%
6	−0.30	1.94	10.51%

Figure 3. Automatic LCPs screening based on the LCP database and land cover (the left is before the process, and the right is after the process).

Figure 4. Automatic association of LCPs and OSSI based on topographic relief.

Figure 5. Experimental area and data (the left is the land cover map, and the right is ZY-3 optical stereo imagery).

Figure 6. Distribution of tie points (left) and ECPs generated from the association of LCPs and OSSI (right).

Table 4. Plane accuracy of the tie points (px).

Period	Mean		Root mean square		Root mean square error		Minimum deviation		Maximum deviation		Number of tie points
	X	Y	X	Y	X	Y	X	Y	X	Y
Before BA	−0.05	0.19	4.28	12.32	4.28	12.32	−24.70	−62.10	30.32	76.78	12,285
After the BA without control points	−0.01	−0.00	0.37	0.45	0.37	0.45	−3.58	−4.23	3.87	4.26	10,203
After the combined BA of LCPs and OSSI	−0.01	−0.00	0.30	0.25	0.30	0.25	−1.00	−1.12	1.32	1.55	10,050

Table 5. Elevation accuracy of the combined BA (m).

Period	Mean	Root mean square	Root mean square error	Minimum deviation	Maximum deviation
Before BA	13.20	13.74	3.88	7.33	21.07
After the BA without control points	0.43	2.91	2.87	−4.36	10.76
After the combined BA of LCPs and OSSI	0.06	1.20	1.18	−3.48	2.92

Figure 7. Elevation accuracy before and after the combined BA (the left is before BA, and the right is after the combined BA).

Tang, X., J. Xie, M. Fan, X. Dou, L. Xin, L. Shaoning, L. Song, et al. 2020. “GF-7 Dual-Beam Laser Altimeter On-Orbit Geometric Calibration.” Acta Geodaetica et Cartographica Sinica 50 (3): 384–395. doi:10.11947/j.AGCS.2021.20200397.

 Google Scholar

Data availability statement

The ZY-3 stereo imagery data that support the findings of this study are restricted in access and use, but can be queried and requested from the website of the China Centre for Resources Satellite Data and Application (CRESDA) (http://www.cresda.com/EN/) and Chinese Natural Resources Satellite Remote Sensing Cloud Service Platform (http://sasclouds.com/chinese/normal/). The ICESat-2 data are openly available and can be acquired from the National Snow & Ice Data Center (NSIDC) at https://nsidc.org/data/. The GlobalLand30 data can be downloaded at https://www.globallandcover.com/.