Estimation of Footprint-Scale Across-Track Slopes Based on Elevation Frequency Histogram from Single-Track ICESat-2 Photon Data of Strong Beam
Topographic slope is a key parameter for characterizing landscape geomorphology. The Ice, Cloud, and Land Elevation Satellite-2 (ICESat-2) offers high-resolution along-track slopes based on the ground profiles generated by dense signal photons. However, the across-track slopes are typically derived...
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MDPI AG
2025-07-01
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| Series: | Remote Sensing |
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| author | Qianyin Zhang Hui Zhou Yue Ma Song Li Heng Wang |
| author_facet | Qianyin Zhang Hui Zhou Yue Ma Song Li Heng Wang |
| author_sort | Qianyin Zhang |
| collection | DOAJ |
| description | Topographic slope is a key parameter for characterizing landscape geomorphology. The Ice, Cloud, and Land Elevation Satellite-2 (ICESat-2) offers high-resolution along-track slopes based on the ground profiles generated by dense signal photons. However, the across-track slopes are typically derived using the ground photon geolocations from the weak-beam and strong-beam pair, limiting the retrieval accuracy and losing valid results over rugged terrains. The goal of this study is to propose a new method to derive the across-track slope merely using single-track photon data of a strong beam based on the theoretical formula of the received signal pulse width. Based on the ICESat-2 photon data over the Walker Lake area, the specific purposes are to (1) extract the along-track slope and surface roughness from the signal photon data on the ground; (2) generate an elevation frequency histogram (EFH) and calculate its root mean square (RMS) width; and (3) derive the across-track slope from the RMS width of the EFH and evaluate the retrieval accuracy against the across-track slope from the ICESat-2 product and plane fitting method. The results show that the mean absolute error (MAE) obtained by our method is 11.45°, which is comparable to the ICESat-2 method (11.61°) and the plane fitting method (12.51°). Our method produces the least invalid data proportion of ~2.5%, significantly outperforming both the plane fitting method (10.29%) and the ICESat-2 method (32.32%). Specifically, when the reference across-track slope exceeds 30°, our method can consistently yield the optimal across-track slopes, where the absolute median, inter quartile range, and whisker range of the across-track slope residuals have reductions greater than 4.44°, 1.31°, and 0.10°, respectively. Overall, our method is well-suited for the across-track slope estimation over rugged terrains and can provide higher-precision, higher-resolution, and more valid across-track slopes. |
| format | Article |
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| institution | Kabale University |
| issn | 2072-4292 |
| language | English |
| publishDate | 2025-07-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Remote Sensing |
| spelling | doaj-art-400b2dc3b8524a5092ca30d8ee6c52732025-08-20T04:00:53ZengMDPI AGRemote Sensing2072-42922025-07-011715261710.3390/rs17152617Estimation of Footprint-Scale Across-Track Slopes Based on Elevation Frequency Histogram from Single-Track ICESat-2 Photon Data of Strong BeamQianyin Zhang0Hui Zhou1Yue Ma2Song Li3Heng Wang4School of Electronic Information, Wuhan University, Wuhan 430072, ChinaSchool of Electronic Information, Wuhan University, Wuhan 430072, ChinaSchool of Electronic Information, Wuhan University, Wuhan 430072, ChinaSchool of Electronic Information, Wuhan University, Wuhan 430072, ChinaSchool of Electronic Information, Wuhan University, Wuhan 430072, ChinaTopographic slope is a key parameter for characterizing landscape geomorphology. The Ice, Cloud, and Land Elevation Satellite-2 (ICESat-2) offers high-resolution along-track slopes based on the ground profiles generated by dense signal photons. However, the across-track slopes are typically derived using the ground photon geolocations from the weak-beam and strong-beam pair, limiting the retrieval accuracy and losing valid results over rugged terrains. The goal of this study is to propose a new method to derive the across-track slope merely using single-track photon data of a strong beam based on the theoretical formula of the received signal pulse width. Based on the ICESat-2 photon data over the Walker Lake area, the specific purposes are to (1) extract the along-track slope and surface roughness from the signal photon data on the ground; (2) generate an elevation frequency histogram (EFH) and calculate its root mean square (RMS) width; and (3) derive the across-track slope from the RMS width of the EFH and evaluate the retrieval accuracy against the across-track slope from the ICESat-2 product and plane fitting method. The results show that the mean absolute error (MAE) obtained by our method is 11.45°, which is comparable to the ICESat-2 method (11.61°) and the plane fitting method (12.51°). Our method produces the least invalid data proportion of ~2.5%, significantly outperforming both the plane fitting method (10.29%) and the ICESat-2 method (32.32%). Specifically, when the reference across-track slope exceeds 30°, our method can consistently yield the optimal across-track slopes, where the absolute median, inter quartile range, and whisker range of the across-track slope residuals have reductions greater than 4.44°, 1.31°, and 0.10°, respectively. Overall, our method is well-suited for the across-track slope estimation over rugged terrains and can provide higher-precision, higher-resolution, and more valid across-track slopes.https://www.mdpi.com/2072-4292/17/15/2617ICESat-2photon dataElevation Frequency Histogrampulse widthacross-track slope |
| spellingShingle | Qianyin Zhang Hui Zhou Yue Ma Song Li Heng Wang Estimation of Footprint-Scale Across-Track Slopes Based on Elevation Frequency Histogram from Single-Track ICESat-2 Photon Data of Strong Beam Remote Sensing ICESat-2 photon data Elevation Frequency Histogram pulse width across-track slope |
| title | Estimation of Footprint-Scale Across-Track Slopes Based on Elevation Frequency Histogram from Single-Track ICESat-2 Photon Data of Strong Beam |
| title_full | Estimation of Footprint-Scale Across-Track Slopes Based on Elevation Frequency Histogram from Single-Track ICESat-2 Photon Data of Strong Beam |
| title_fullStr | Estimation of Footprint-Scale Across-Track Slopes Based on Elevation Frequency Histogram from Single-Track ICESat-2 Photon Data of Strong Beam |
| title_full_unstemmed | Estimation of Footprint-Scale Across-Track Slopes Based on Elevation Frequency Histogram from Single-Track ICESat-2 Photon Data of Strong Beam |
| title_short | Estimation of Footprint-Scale Across-Track Slopes Based on Elevation Frequency Histogram from Single-Track ICESat-2 Photon Data of Strong Beam |
| title_sort | estimation of footprint scale across track slopes based on elevation frequency histogram from single track icesat 2 photon data of strong beam |
| topic | ICESat-2 photon data Elevation Frequency Histogram pulse width across-track slope |
| url | https://www.mdpi.com/2072-4292/17/15/2617 |
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