Improving Estimates of Soil Salt Content by Using Two-Date Image Spectral Changes in Yinbei, China
Abstract
:1. Introduction
2. Materials and Methods
2.1. Study Area
2.2. Soil Sampling and Chemical Analysis
2.3. Time-Series Image Collection and Pre-Processing
2.4. Modelling Strategies
2.4.1. Detecting the Two-Date Images Spectral Changes
2.4.2. Two-Date-Based Spectral Index Construction
2.4.3. Random Forest Algorithm
2.5. Statistical Analysis
3. Results
3.1. Characteristics of Soil Properties and Reflectance Spectra
3.2. Optimal Two-Date Satellite Images
3.3. Sensitive Spectral Parameters
3.4. Performance Assessment of Prediction Models Built with Different Inputs
3.5. Map of Soil Salt Contents
4. Discussion
4.1. Characterizing Temporal Changes in Salt-Induced Spectral Information for Improving SSC Estimation
4.2. Robustness of the Model Built with Two-Date-Based Indices
4.3. Uncertainty Analysis
5. Conclusions
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Acknowledgments
Conflicts of Interest
References
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Band Acronym | B1 | B2 | B3 | B4 | B5 | B6 | B7 | B8 | B8a | B9 | B10 | B11 | B12 |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Band centre/nm | 443 | 490 | 560 | 665 | 705 | 740 | 775 | 842 | 865 | 940 | 1375 | 1610 | 2190 |
Band width/nm | 20 | 65 | 35 | 30 | 15 | 15 | 20 | 115 | 20 | 20 | 30 | 90 | 180 |
Number | Input Variables | Data Sources |
---|---|---|
1 | Sensitive spectral bands | The simultaneous image |
2 | Optimal two-date-based indices | The two-date images |
3 | Sensitive spectral bands and optimal two-date-based spectral indices | The two-date images |
Index Abbreviation | Calculation Image | Equation |
---|---|---|
Dij | t0, t1 | Bi − Bj |
Rij | t0, t1 | Bi/Bj |
NDij | t0, t1 | (Bi − Bj)/(Bi + Bj) |
tanimj | t0, t1 | (kim − kmj)/(1 + kim·kmj) |
Band Acronym | B2 | B3 | B4 | B5 | B6 | B7 | B8 | B8a | B11 | B12 |
---|---|---|---|---|---|---|---|---|---|---|
SSC | 0.49 * | 0.46 | 0.47 | 0.47 | 0.48 | 0.48 * | 0.49 ** | 0.49 ** | 0.50 ** | 0.41 * |
Number | Satellite Platform | Capture Time of Two-Date Images | Optimal Inputs | R2 | RPD |
---|---|---|---|---|---|
1 | Sentinel-2_MSI data | October 2017 and April 2018 | B2, B8, B8a, B11, B12, and ND8a8a | 0.79 | 1.45 |
2 | November 2017 and April 2018 | B2, B8, B8a, B11, B12, and D22 | 0.85 | 2.43 | |
3 | January 2018 and April 2018 | B2, B8, B8a, B11, B12, D22, and D28a | 0.87 | 2.72 | |
4 | February 2018 and April 2018 | B2, B8, B8a, B11, B12, D22, and D28a | 0.82 | 1.93 | |
5 | March 2018 and April 2018 | B2, B8, B8a, B11, B12, and tan28a11 | 0.82 | 1.82 | |
6 | Landsat-8_OLI data | April 2018 | B4, B5, B6, and B7 | 0.72 | 1.25 |
7 | December 2017 and April 2018 | B4, B5, B6, B7, and D55 | 0.81 | 1.91 |
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Xu, X.; Chen, Y.; Wang, M.; Wang, S.; Li, K.; Li, Y. Improving Estimates of Soil Salt Content by Using Two-Date Image Spectral Changes in Yinbei, China. Remote Sens. 2021, 13, 4165. https://doi.org/10.3390/rs13204165
Xu X, Chen Y, Wang M, Wang S, Li K, Li Y. Improving Estimates of Soil Salt Content by Using Two-Date Image Spectral Changes in Yinbei, China. Remote Sensing. 2021; 13(20):4165. https://doi.org/10.3390/rs13204165
Chicago/Turabian StyleXu, Xibo, Yunhao Chen, Mingguo Wang, Sijia Wang, Kangning Li, and Yongguang Li. 2021. "Improving Estimates of Soil Salt Content by Using Two-Date Image Spectral Changes in Yinbei, China" Remote Sensing 13, no. 20: 4165. https://doi.org/10.3390/rs13204165