Fig. 1. Structure of tandem 3D-2D-CNN
Fig. 2. Schematic of standard convolution and dilated convolution. (a) 2D standard convolution; (b) 2D dilated convolution (r=2,2); (c) 3D standard convolution; (d) 3D dilated convolution (r=2,2,2)
Fig. 3. Multi-scale feature fusion structure. (a) Multi-scale spatial-spectral feature fusion module; (b) multi-scale spatial feature fusion module
Fig. 4. Structure diagram of attention module. (a) Spatial-spectral attention module; (b) spatial attention module
Fig. 5. Overall structure of proposed network
Fig. 6. False color image and ground truth of data sets. (a) PU data set; (b) SA data set
Fig. 7. Comparison of accuracy for different spatial sizes. (a) PU data set; (b) SA data set
Fig. 8. Classification maps and partial enlarged maps with different algorithms on PU data set. (a) Ground truth image; (b) 2D-CNN-MLP; (c) 3D-CNN-CRF; (d) Hybrid-CNN; (e) Dilated-3D-CNN; (f) 3D-2D-ADCNN
Fig. 9. Classification maps with different algorithms on SA data set. (a) Ground truth image; (b) 2D-CNN-MLP; (c) 3D-CNN-CRF; (d) Hybrid-CNN; (e) Dilated-3D-CNN; (f) 3D-2D-ADCNN
Fig. 10. Overall accuracy with different numbers of training samples. (a) PU data set; (b) SA data set
Kernel number | Pavia University | Salinas |
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OA /% | Training time /s | Test time /s | OA /% | Training time /s | Test time /s |
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16 | 97.78 | 118.03 | 29.71 | 96.48 | 243.42 | 66.38 | 20 | 96.87 | 130.56 | 34.19 | 97.28 | 324.71 | 76.93 | 24 | 97.17 | 149.93 | 38.34 | 96.26 | 373.57 | 88.24 | 28 | 96.25 | 185.74 | 43.35 | 95.88 | 383.83 | 98.84 | 32 | 97.05 | 165.58 | 46.76 | 96.12 | 416.47 | 107.36 |
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Table 1. Comparison of overall accuracy, training time, and test time for different convolution kernel numbers
Architecture | Pavia University | Salinas |
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Parameter | OA /% | Parameter | OA /% |
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3D-2D-CNN (baseline) | 75596 | 98.11 | 139644 | 98.03 | 3D-2D-CNN+dilated convolution | 56783 | 98.47 | 110402 | 98.42 | 3D-2D-CNN+attention | 75643 | 98.51 | 139718 | 98.38 | 3D-2D-CNN+dilated convolution+attention | 56857 | 98.73 | 110476 | 98.61 |
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Table 2. Comparison of parameters and overall accuracy for different model architectures
Category name | 2D-CNN-MLP | 3D-CNN-CRF | Hybrid-CNN | Dilated-3D-CNN | 3D-2D-ADCNN |
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Asphalt | 87.33 | 86.78 | 90.89 | 84.86 | 96.82 | Meadows | 90.46 | 86.51 | 96.31 | 87.67 | 99.47 | Gravels | 84.91 | 85.76 | 94.45 | 87.73 | 99.35 | Trees | 93.00 | 96.27 | 92.39 | 97.71 | 97.77 | Painted-Metal-Sheets | 99.72 | 99.90 | 99.78 | 99.75 | 99.92 | Bare-Soil | 88.46 | 85.18 | 99.06 | 85.94 | 100.00 | Bitumen | 94.67 | 93.23 | 99.24 | 89.33 | 99.84 | Self-Blocking-Bricks | 85.04 | 86.74 | 87.81 | 83.76 | 98.91 | Shadows | 98.94 | 99.11 | 96.87 | 99.82 | 98.57 | OA | 89.76 | 87.92 | 94.89 | 89.48 | 98.75 | AA | 91.39 | 91.05 | 95.20 | 89.89 | 98.96 | Kappa | 96.54 | 84.22 | 93.26 | 86.04 | 98.60 |
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Table 3. Comparison of classification accuracy for different algorithms on PU data setunit: %
Category name | 2D-CNN-MLP | 3D-CNN-CRF | Hybrid-CNN | Dilated-3D-CNN | 3D-2D-ADCNN |
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Brocoli_green_weeds_1 | 99.98 | 99.39 | 99.99 | 99.97 | 100.00 | Brocoli_green_weeds_2 | 99.48 | 98.92 | 99.96 | 99.70 | 100.00 | Fallow | 99.27 | 99.59 | 98.57 | 99.08 | 100.00 | Fallow_rough_plow | 99.30 | 99.16 | 99.47 | 99.47 | 99.61 | Fallow_smooth | 98.44 | 97.44 | 98.65 | 96.86 | 99.80 | Stubble | 99.76 | 99.94 | 99.79 | 99.76 | 100.00 | Celery | 99.61 | 99.60 | 99.84 | 99.60 | 100.00 | Grapes_untrained | 79.40 | 76.09 | 88.90 | 70.83 | 94.17 | Soil_vinyard_develop | 99.92 | 99.73 | 98.61 | 99.05 | 100.00 | Corn_senesced_green_weeds | 95.61 | 94.52 | 99.18 | 92.72 | 100.00 | Lettuce_romaine_4wk | 99.02 | 99.29 | 99.82 | 98.78 | 100.00 | Lettuce_romaine_5wk | 99.99 | 99.88 | 99.01 | 99.92 | 100.00 | Lettuce_romaine_6wk | 99.98 | 99.78 | 99.52 | 99.33 | 100.00 | Lettuce_romaine_7wk | 98.86 | 99.01 | 99.41 | 99.38 | 99.89 | Vinyard_untrained | 81.90 | 79.83 | 94.71 | 81.40 | 99.09 | Vinyard_vertical_trellis | 98.05 | 97.14 | 99.81 | 98.36 | 100.00 | OA | 92.57 | 91.38 | 96.48 | 90.25 | 98.61 | AA | 96.79 | 96.21 | 98.45 | 95.82 | 99.53 | Kappa | 91.73 | 90.40 | 96.09 | 89.17 | 98.45 |
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Table 4. Comparison of classification accuracy for different algorithms on SA data setunit: %
Item | 2D-CNN-MLP | 3D-CNN-CRF | Hybrid-CNN | Dilated-3D-CNN | 3D-2D-ADCNN |
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Parameter | 33129 | 155017 | 4844793 | 413801 | 56857 | Training time /s | 8.91 | 103.30 | 63.75 | 671.89 | 122.22 | Test time /s | 2.17 | 13.04 | 7.85 | 72.36 | 51.93 |
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Table 5. Comparison of parameters, training time, and test time for different algorithms on PU data set
Item | 2D-CNN-MLP | 3D-CNN-CRF | Hybrid-CNN | Dilated-3D-CNN | 3D-2D-ADCNN |
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Parameter | 33556 | 192144 | 4845696 | 498912 | 110476 | Training time /s | 16.94 | 276.08 | 97.08 | 2122.97 | 327.33 | Test time /s | 2.70 | 27.69 | 9.70 | 170.50 | 122.61 |
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Table 6. Comparison of parameters, training time, and test time for different algorithms on SA data set