A Highland Barley Crop Extraction Method Based on Optimized Feature Combination of Multiple Phenological Sentinel-2 Images
Abstract
:1. Introduction
2. Materials and Methods
2.1. Study Area
2.2. Data Source and Preprocessing
2.3. Sample Data
2.4. Methods
2.4.1. Feature Set Construction
2.4.2. Principal Component Analysis (PCA)
2.4.3. GrayScale Covariance Matrix
2.4.4. Random Forest Algorithm
- (1)
- Construction, calibration, and variables of the random forest model
- (2)
- Crop information extraction and classification
- (3)
- Importance discrimination of characteristic variables
2.4.5. Accuracy Assessment
3. Results
3.1. Importance Ranking of Characteristic Variables
3.2. The Optimal Combination of Crop Classification Characteristics in Different Phenological Periods
3.3. Analysis of Spatial Distribution of Highland Barley in Different Time Phases
4. Discussion
5. Conclusion
- (1)
- The overall classification accuracy of information extraction was better after feature optimization and the combination of multitemporal image data. The optimal phenological periods for highland barley extraction were the jointing stage and the milk ripening stage. For highland barley crops, the overall accuracy at the jointing stage was 92.56%, with a kappa coefficient of 0.86. The overall accuracy at the milk ripening stage was 91.55%, with a kappa coefficient of 0.84.
- (2)
- The importance score of the red edge index based on the Sentinel-2 image data was higher in the feature selection combination. The red edge index had a higher contribution rate in the process of crop information extraction and classification.
- (3)
- The five characteristic variables—GLCM_Mean, RVI, homogeneity, MAX, and GLCM_Correlation—were applicable to the information extraction of crops in Chengbei District and played a very important role in the classification of different phenological periods. These five characteristic variables were stable and universal throughout the process of crop extraction.
Author Contributions
Funding
Institutional Review Board Statement
Data Availability Statement
Acknowledgments
Conflicts of Interest
References
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Bands | Central Wavelength (nm) | Bandwidth (nm) | Resolution (m) |
---|---|---|---|
B1: Coast/aerosol band | 443 | 20 | 60 |
B2: Blue band | 490 | 65 | 10 |
B3: Green band | 560 | 35 | 10 |
B4: Red band | 665 | 30 | 10 |
B5: Vegetation red edge (band 1) | 705 | 15 | 20 |
B6: Vegetation red edge (band 2) | 740 | 15 | 20 |
B7: Vegetation red edge (band 3) | 783 | 20 | 20 |
B8: Near-infrared band (wide) | 842 | 115 | 10 |
B8A: Near-infrared band (narrow) | 865 | 20 | 20 |
B9: Water vapor band | 945 | 20 | 60 |
B10: Cirrus band | 1375 | 20 | 60 |
B11: Short-wave infrared (band 1) | 1610 | 90 | 20 |
B12: Short-wave infrared (band 2) | 2190 | 180 | 20 |
Image Date | 0616 | 0706 | 0726 | 0811 | 0825 |
---|---|---|---|---|---|
Phenological period of highland barley | Jointing stage | Heading stage | Flowering stage | Milk ripening stage | Maturity stage |
Characteristic Variable Set | Characteristic Variable | Explanation/Calculation Formula | Main References |
---|---|---|---|
Spectral Signature | Band | B2, B3, B4, B5, B6, B7, B8, B8A, B11, B12 | -- |
Texture Features | Angular Second Moment (ASM) | -- | |
Contrast | -- | ||
Dissimilarity | -- | ||
Energy | -- | ||
Entropy | -- | ||
Homogeneity | -- | ||
MAX | -- | ||
GLCM_Correlation | -- | ||
GLCM_Mean | -- | ||
GLCM_Variance | -- | ||
Vegetation Index | Normalized Difference Vegetation Index (NDVI) | [15,16,17] | |
Ratio Vegetation Index (RVI) | |||
Difference Vegetation Index (DVI) | |||
Modified Soil-Adjusted Vegetation Index (MSAVI) | |||
Soil-Adjusted Vegetation Index (SAVI) | |||
Water Index | Normalized Difference Water Index (NDWI) | ||
Modified Normalized Difference Water Index (MNDWI) | |||
Red Edge Index | Red Edge Normalized Difference Vegetation Index (RNDVI) | [18] | |
Red Edge Chlorophyll Index (CIre) | |||
Modified Simple Ratio Red Edge Index (MSRre) | |||
Red Edge Normalized Difference Vegetation Index 1 (NDVIre1) | |||
Red Edge Normalized Difference Vegetation Index 2 (NDVIre2) | |||
Red Edge Normalized Difference Vegetation Index 3 (NDVIre3) | |||
Red Edge Normalized Difference 1 (NDre1) | |||
Red Edge Normalized Difference 2 (NDre2) |
Principal Component Analysis | Contribution Rate |
---|---|
PCA_1 | 83.5% |
PCA_2 | 9.8% |
PCA_3 | 4.5% |
Phenophase | Optimal Combination of Features |
---|---|
Jointing Stage | PCA_1, PCA_2, PCA_3, NDVIre1, GLCM_Variance, NDVIre3, SAVI, NDre1, Energy, MSRre, Homogeneity, GLCM_Correlation, NDVI, Dissimilarity, MAX, NDWI, MNDWI, DVI, RVI, MSAVI |
Heading Stage | PCA_1, PCA_2, PCA_3, NDVIre1, GLCM_Mean, GLCM_Variance, NDVIre3, SAVI, NDre1, Energy, MSRre, Homogeneity, GLCM_Correlation, NDVI, Dissimilarity, MAX, NDWI, MNDWI, DVI, RVI, MSAVI |
Flowering Stage | PCA_1, PCA_2, PCA_3, GLCM_Mean, NDVIre1, GLCM_Correlation, CIre, MSRre, GLCM_Variance, Homogeneity, Contrast, RVI, NDWI, MNDWI, ASM, MAX, SAVI, Dissimilarity |
Milk Ripening Stage | PCA_1, PCA_2, PCA_3, RNDVI, GLCM_Mean, GLCM_Variance, NDre1, GLCM_Correlation, Entropy, NDVIre3, RVI, Homogeneity, MAX, Energy, ASM, NDVIre2, NDre2, DVI, NDVI, NDVIre1 |
Maturity Stage | PCA_1, PCA_2, PCA_3, NDre1, RNDVI, GLCM_Mean, MNDWI, GLCM_Correlation, NDWI, RVI, NDVIre3, MAX, Entropy, CIre, Energy, Homogeneity, MSAVI, SAVI, DVI |
Phenophase | Jointing Stage | Heading Stage | Flowering Stage | Milk Ripening Stage | Maturity Stage | |||||
---|---|---|---|---|---|---|---|---|---|---|
Evaluation Index | PA (%) | UA (%) | PA (%) | UA (%) | PA (%) | UA (%) | PA (%) | UA (%) | PA (%) | UA (%) |
Highland Barley | 89.65 | 88.53 | 90.24 | 82.51 | 91.86 | 82.80 | 95.87 | 86.39 | 93.85 | 87.51 |
Other Crops | 48.36 | 77.18 | 30.77 | 50.16 | 37.68 | 45.61 | 40.77 | 45.21 | 30.14 | 67.46 |
Mountainous Areas | 96.07 | 95.64 | 95.42 | 94.87 | 93.69 | 95.94 | 93.92 | 96.59 | 93.61 | 94.14 |
Urban Areas | 99.09 | 84.47 | 95.70 | 91.95 | 98.79 | 91.06 | 98.48 | 91.17 | 99.61 | 79.31 |
Water Bodies | 94.96 | 100.00 | 98.05 | 100.00 | 98.70 | 100.00 | 91.38 | 100.00 | 90.73 | 100.00 |
OA (%) | 92.56 | 90.90 | 90.74 | 91.55 | 90.51 | |||||
Kappa | 0.86 | 0.82 | 0.82 | 0.84 | 0.82 |
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Wu, X.; Pan, K.; Zhang, L.; He, X.; Wang, L.; Guo, B. A Highland Barley Crop Extraction Method Based on Optimized Feature Combination of Multiple Phenological Sentinel-2 Images. Agriculture 2024, 14, 1466. https://doi.org/10.3390/agriculture14091466
Wu X, Pan K, Zhang L, He X, Wang L, Guo B. A Highland Barley Crop Extraction Method Based on Optimized Feature Combination of Multiple Phenological Sentinel-2 Images. Agriculture. 2024; 14(9):1466. https://doi.org/10.3390/agriculture14091466
Chicago/Turabian StyleWu, Xiaogang, Kaiwen Pan, Lin Zhang, Xiulin He, Longhao Wang, and Bing Guo. 2024. "A Highland Barley Crop Extraction Method Based on Optimized Feature Combination of Multiple Phenological Sentinel-2 Images" Agriculture 14, no. 9: 1466. https://doi.org/10.3390/agriculture14091466