A high-quality global elevation control point dataset from ICESat-2 altimeter data

Figures & data

Figure 1. Validation areas for the elevation control points. (a) The geolocation (red points) of nine validation areas within the global land areas. (b) – (j) The distributions of the high-resolution DEMs (white line areas) and the elevation control points (blue points) within each validation area. I-X indicate the number of the study areas.

Table 1. The Characteristics of the DEMs.

Area	Survey year	Resolution (m)	Elevation RMSE (m)
I	2020–2021	0.5	∼0.1
II	2017	0.5	∼0.05
III	2016–2017	1	∼0.05
IV	2018	1	∼0.07
V	2018	0.5	∼0.07
VI	2018–2020	1	∼0.1
VII	2020	1	∼0.1
VIII	2020–2021	1	∼0.1
X	2020	1	∼0.06

Figure 2. Schematic diagram for the construction of the dataset.

Table 2. Data Dictionary of the Dataset.

No.	Type	Label	Description
1	Double	Time	Survey time: the time in seconds relative to the GPS epoch (19800106T00:00:00.000000Z UTC)
2	Single	Lon	Latitude of the elevation control points (WGS84)
3	Single	Lat	Longitude of the elevation control points (WGS84)
4	Single	Elevation	Elevation of the elevation control points (WGS84)
5	Uint8	Beam	The values of the labels are 1, 2, 3, 4, 5, and 6. 1–3 and 4–6 indicate that the elevation was sourced from the strong beam and weak beam, respectively.
6	Uint8	Level	The levels of elevation quality are 1, 2, and 3. These values indicate that the RMSE of the elevation is less than 0.5 , 0.7 , and 1.5 m, respectively.

Figure 3. Distribution of elevation control points in the dataset

Table 3. Accuracy Analysis of the Elevation Control Points Within Each Validation Region.

No.		I	II	III	IV	V	VI	VII	VII	VIII
Proportion of samples (%)	Level 1	98.94	83.26	98.61	93.32	81.67	34.21	92.77	86.97	66.88
	Level 2	1.01	15.25	1.24	6.60	15.20	51.31	4.78	10.84	20.51
	Level 3	0.05	1.49	0.15	0.08	3.13	14.48	2.44	2.18	12.61
Elevation RMSE (m)	Level 1	0.25	0.41	0.28	0.23	0.37	0.48	0.20	0.31	0.28
	Level 2	0.49	0.47	0.57	0.25	0.55	0.48	0.43	0.45	0.40
	Level 3	0.51	0.59	0.70	0.35	0.85	0.55	0.64	0.64	0.49
	All	0.25	0.42	0.28	0.23	0.43	0.49	0.23	0.34	0.34

Figure 4. Histogram statistics for the elevation control points within the validation areas. (a) – (c) Statistics of the elevation control points with levels 1 - 3, corresponding to flat, hilly and mountainous areas along track, respectively.

Table 4. Accuracy Comparison of the Strong and Weak Beams’ Elevation Control Points.

Beam	Level	Original elevation RMSE (m)	Dataset elevation RMSE (m)
Strong	1	1.46	0.26
	2	3.46	0.40
	3	4.62	0.69
	All	2.19	0.28
Weak	1	1.28	0.31
	2	2.95	0.46
	3	5.04	0.58
	All	2.07	0.32

Table 5. Accuracy Comparison of the Elevation Control Points Within Urban and Non-Urban Areas.

Land cover	Original elevation RMSE (m)	Dataset elevation RMSE (m)
Urban	1.74	0.33
Non-urban	2.16	0.30

Figure 5. Distribution of the dataset within the different vegetation cover indices.

Figure 6. Proportions of the dataset within the different vegetation cover indices.

Figure 7. Accuracy analysis of the elevation control points within the different vegetation cover indices. (a) – (c) The sample number, RMSE, and elevation error of the original elevations and the dataset elevations, respectively.

Figure 8. Statistics for the elevation control points within the global 0.25°×0.25° grid.

Figure 9. Statistics for the original elevation points within the global 0.25°×0.25° grid.

Data availability statement

The data that support the findings of this study are openly available in National Tibetan Plateau / Third Pole Environment Data Center at https://doi.org/10.11888/Terre.tpdc.300508

 Google Scholar

(Xie et al. 2023).