Figure 1.
The distribution map of the study area and the field survey points.
Figure 1.
The distribution map of the study area and the field survey points.
Figure 2.
Spectral response functions of Jilin-1 GP01/02 PMS and MODIS in visible to near-infrared bands.
Figure 2.
Spectral response functions of Jilin-1 GP01/02 PMS and MODIS in visible to near-infrared bands.
Figure 3.
Spectral response functions of Jilin-1 GP01/02 PMS and Landsat TM in visible to near-infrared bands.
Figure 3.
Spectral response functions of Jilin-1 GP01/02 PMS and Landsat TM in visible to near-infrared bands.
Figure 4.
VIs-based LAI, FVC, and chlorophyll (T850 nm/T720 nm) estimations. The X-axis is the vegetation index, the left Y-axis is the R2 value, and the right Y-axis is the RMSE value. (a) LAI, (b) FVC, and (c) chlorophyll (T850 nm/T720 nm).
Figure 4.
VIs-based LAI, FVC, and chlorophyll (T850 nm/T720 nm) estimations. The X-axis is the vegetation index, the left Y-axis is the R2 value, and the right Y-axis is the RMSE value. (a) LAI, (b) FVC, and (c) chlorophyll (T850 nm/T720 nm).
Figure 5.
Green band reflectance validation based on field measured data. The X-axis is the measured reflectance, the Y-axis is the corrected reflectance, the black solid line is the 1:1 line, and the different color scatter points represent the different observation geometry. (a) Original, (b) MODIS-based, (c) AFX, (d) VJB, (e) Fixed-Landsat, And (f) Fixed-Jilin-1.
Figure 5.
Green band reflectance validation based on field measured data. The X-axis is the measured reflectance, the Y-axis is the corrected reflectance, the black solid line is the 1:1 line, and the different color scatter points represent the different observation geometry. (a) Original, (b) MODIS-based, (c) AFX, (d) VJB, (e) Fixed-Landsat, And (f) Fixed-Jilin-1.
Figure 6.
Red band reflectance validation based on field measured data. The X-axis is the measured reflectance, the Y-axis is the corrected reflectance, the black solid line is the 1:1 line, and the different color scatter points represent the different observation geometry. (a) Original, (b) MODIS-based, (c) AFX, (d) VJB, (e) Fixed-Landsat, And (f) Fixed-Jilin-1.
Figure 6.
Red band reflectance validation based on field measured data. The X-axis is the measured reflectance, the Y-axis is the corrected reflectance, the black solid line is the 1:1 line, and the different color scatter points represent the different observation geometry. (a) Original, (b) MODIS-based, (c) AFX, (d) VJB, (e) Fixed-Landsat, And (f) Fixed-Jilin-1.
Figure 7.
NIR band reflectance validation based on field measured data. The X-axis is the measured reflectance, the Y-axis is the corrected reflectance, the black solid line is the 1:1 line, and the different color scatter points represent the different observation geometry. (a) Original, (b) MODIS-based, (c) AFX, (d) VJB, (e) Fixed-Landsat, And (f) Fixed-Jilin-1.
Figure 7.
NIR band reflectance validation based on field measured data. The X-axis is the measured reflectance, the Y-axis is the corrected reflectance, the black solid line is the 1:1 line, and the different color scatter points represent the different observation geometry. (a) Original, (b) MODIS-based, (c) AFX, (d) VJB, (e) Fixed-Landsat, And (f) Fixed-Jilin-1.
Figure 8.
LAI validation based on field measured data. The X-axis is the measured reflectance, the Y-axis is the corrected reflectance, and the black solid line is the 1:1 line. (a) Original, (b) MODIS-based, (c) AFX, (d) VJB, (e) Fixed-Landsat, and (f) Fixed-Jilin-1.
Figure 8.
LAI validation based on field measured data. The X-axis is the measured reflectance, the Y-axis is the corrected reflectance, and the black solid line is the 1:1 line. (a) Original, (b) MODIS-based, (c) AFX, (d) VJB, (e) Fixed-Landsat, and (f) Fixed-Jilin-1.
Figure 9.
FVC validation based on field-measured data. The X-axis is the measured reflectance, the Y-axis is the corrected reflectance, and the black solid line is the 1:1 line. (a) Original, (b) MODIS-based, (c) AFX, (d) VJB, (e) Fixed-Landsat, and (f) Fixed-Jilin-1.
Figure 9.
FVC validation based on field-measured data. The X-axis is the measured reflectance, the Y-axis is the corrected reflectance, and the black solid line is the 1:1 line. (a) Original, (b) MODIS-based, (c) AFX, (d) VJB, (e) Fixed-Landsat, and (f) Fixed-Jilin-1.
Figure 10.
Chlorophyll (T850 nm/T720 nm) validation based on field measured data. The X-axis is the measured reflectance, the Y-axis is the corrected reflectance, and the black solid line is the 1:1 line. (a) Original, (b) MODIS-based, (c) AFX, (d) VJB, (e) Fixed-Landsat, and (f) Fixed-Jilin-1.
Figure 10.
Chlorophyll (T850 nm/T720 nm) validation based on field measured data. The X-axis is the measured reflectance, the Y-axis is the corrected reflectance, and the black solid line is the 1:1 line. (a) Original, (b) MODIS-based, (c) AFX, (d) VJB, (e) Fixed-Landsat, and (f) Fixed-Jilin-1.
Table 1.
Sites, time, crop type, and growing season information for field survey.
Table 1.
Sites, time, crop type, and growing season information for field survey.
Sites | Crop Type | Time | Crop Growing Season | Number of Survey Points |
---|
Hangjin Rear Banner | Corn, Sunflower | 17 July 2021–18 July 2021 | Flowering Period | 22 |
Urat Front Banner | Corn, Sunflower | 19 July 2021–20 July 2021 20 August 2021–22 August 2021 | Flowering Period Grouting Period | 10 15 |
Zhenglan Banner | Corn, Sunflower | 09 September 2021–11 September 2021 | Grouting Period | 22 |
Horqin Right Front Banner | Corn, Rice | 15 September 2021–18 September 2021 | Ripe Period | 56 |
Table 2.
Technical specifications of Jilin-1 GP01/02 PMS.
Table 2.
Technical specifications of Jilin-1 GP01/02 PMS.
Band | Spectral Range (nm) | Spatial Resolution (m) |
---|
B0 | 450–800 | 5 |
B1 | 403–423 | 5 |
B2 | 433–453 | 5 |
B3 | 450–515 | 5 |
B4 | 525–600 | 5 |
B5 | 630–680 | 5 |
B6 | 784.5–899.5 | 5 |
B7 | 485–495 | 10 |
B8 | 615–625 | 10 |
B9 | 650–680 | 10 |
B10 | 698.75–718.75 | 10 |
B11 | 732.5–747.5 | 10 |
B12 | 773–793 | 10 |
B13 | 855–875 | 20 |
B14 | 660–670 | 20 |
B15 | 677.5–685 | 20 |
B16 | 750–757.5 | 20 |
B17 | 758.75–762.75 | 20 |
B18 | 935–955 | 20 |
B19 | 1000–1040 | 20 |
Table 3.
A list of Jilin-1 GP01/02 PMS data quasi-synchronized with the field survey.
Table 3.
A list of Jilin-1 GP01/02 PMS data quasi-synchronized with the field survey.
Date | Sensors | Solar Zenith Angle | View Zenith Angle | Relative Azimuth Angle |
---|
18/07/2021 | Jilin-1 GP01 PMS2 | 20.33° | 7.93° | 19.73° |
19/07/2021 | Jilin-1 GP01 PMS1 | 20.06° | 16.12° | 56.17° |
19/08/2021 | Jilin-1 GP02 PMS2 | 28.31° | 17.49° | 57.41° |
08/09/2021 | Jilin-1 GP02 PMS1 | 36.53° | 23.85° | 66.24° |
11/09/2021 | Jilin-1 GP01 PMS1 | 37.73° | 8.27° | 21.20° |
17/09/2021 | Jilin-1 GP02 PMS2 | 44.58° | 10.16° | 43.51° |
Table 4.
AFX ranges of six BRDF archetypes in normalized (, , and ) forms in the MODIS green, red, and NIR bands.
Table 4.
AFX ranges of six BRDF archetypes in normalized (, , and ) forms in the MODIS green, red, and NIR bands.
Band | Archetype Number | AFX Range | | | |
---|
Green | 1 | (0.381, 0.714) | 0.5 | 0.0519 | 0.1384 |
2 | (0.714, 0.834) | 0.5 | 0.1906 | 0.1055 |
3 | (0.834, 0.920) | 0.5 | 0.2700 | 0.0806 |
4 | (0.920, 1.012) | 0.5 | 0.3240 | 0.0587 |
5 | (1.012, 1.160) | 0.5 | 0.4337 | 0.0329 |
6 | (1.160, 1.717) | 0.5 | 0.7446 | 0.0072 |
Red | 1 | (0.382, 0.680) | 0.5 | 0.0288 | 0.1426 |
2 | (0.680, 0.795) | 0.5 | 0.1282 | 0.1134 |
3 | (0.795, 0.899) | 0.5 | 0.2029 | 0.0845 |
4 | (0.899, 1.026) | 0.5 | 0.3082 | 0.0585 |
5 | (1.026, 1.240) | 0.5 | 0.4826 | 0.0274 |
6 | (1.240, 1.946) | 0.5 | 1.0859 | 0.0088 |
NIR | 1 | (0.541, 0.804) | 0.5 | 0.1218 | 0.1096 |
2 | (0.804, 0.896) | 0.5 | 0.2377 | 0.0860 |
3 | (0.896, 0.966) | 0.5 | 0.3135 | 0.0679 |
4 | (0.966, 1.042) | 0.5 | 0.3521 | 0.0477 |
5 | (1.042, 1.142) | 0.5 | 0.4321 | 0.0262 |
6 | (1.142, 1.361) | 0.5 | 0.5657 | 0.0040 |
Table 5.
The fixed BRDF parameters for Landsat TM green, red, and NIR bands.
Table 5.
The fixed BRDF parameters for Landsat TM green, red, and NIR bands.
Landsat Band | | | |
---|
2 Green | 0.1306 | 0.0580 | 0.0178 |
3 Red | 0.1690 | 0.0574 | 0.0227 |
4 NIR | 0.3093 | 0.1535 | 0.0330 |
Table 6.
AFXs and normalized BRDF parameters for green, red, and NIR bands of Jilin-1 GP01/02 PMS.
Table 6.
AFXs and normalized BRDF parameters for green, red, and NIR bands of Jilin-1 GP01/02 PMS.
Jilin-1 GP01/02 PMS Band | AFX | | | |
---|
4 Green | 0.8963 | 0.5 | 0.2700 | 0.0806 |
5 Red | 0.8792 | 0.5 | 0.2029 | 0.0845 |
6 NIR | 0.9469 | 0.5 | 0.3135 | 0.0679 |
Table 7.
Vegetation indices used in this research (NIR, red, and green correspond to Jilin-1 GP01/02 PMS band 4, band 3, and band 2, respectively).
Table 7.
Vegetation indices used in this research (NIR, red, and green correspond to Jilin-1 GP01/02 PMS band 4, band 3, and band 2, respectively).
Vegetation Index | Equation |
---|
Ratio Vegetation Index (RVI) | |
Normalized Difference Vegetation Index (NDVI) | |
Green NDVI (GNDVI) | |
Green Chlorophyll Vegetation Index (GCVI) | |
Enhanced Vegetation Index 2 (EVI2) | |
Modified Soil-Adjusted Vegetation Index (MSAVI) | |
Modified Triangular Vegetation Index 2 (MTVI2) | |
Table 8.
Regression analysis between VIs and the LAI, FVC, chlorophyll (T850 nm/T720 nm).
Table 8.
Regression analysis between VIs and the LAI, FVC, chlorophyll (T850 nm/T720 nm).
Crop Parameters | Regression | R2 | RMSE |
---|
LAI | | 0.84 | 0.73 |
FVC | | 0.81 | 6.9% |
chlorophyll (T850 nm/T720 nm) | | 0.85 | 0.15 |
Table 9.
Correction coefficient () of the Jilin-1 GP01/02 PMS in the green, red, and NIR bands under five methods.
Table 9.
Correction coefficient () of the Jilin-1 GP01/02 PMS in the green, red, and NIR bands under five methods.
| MODIS-Based | AFX | VJB | Fixed-Landsat | Fixed-Jilin-1 |
---|
Mean | Std | Mean | Std | Mean | Std | Mean | Std | Mean | Std |
---|
| Green | 0.960 | 0.008 | 0.958 | 0.006 | 0.855 | 0.042 | 0.964 | 0.003 | 0.957 | 0.004 |
Red | 0.961 | 0.010 | 0.957 | 0.007 | 0.848 | 0.056 | 1.031 | 0.002 | 0.959 | 0.003 |
NIR | 0.973 | 0.006 | 0.964 | 0.006 | 0.915 | 0.030 | 0.968 | 0.003 | 0.959 | 0.003 |
| Green | 0.977 | 0.003 | 0.972 | 0.001 | 0.848 | 0.034 | 0.977 | 0.000 | 0.972 | 0.000 |
Red | 0.980 | 0.005 | 0.974 | 0.001 | 0.836 | 0.046 | 1.044 | 0.000 | 0.975 | 0.000 |
NIR | 0.978 | 0.004 | 0.973 | 0.001 | 0.913 | 0.035 | 0.978 | 0.000 | 0.972 | 0.000 |
| Green | 0.955 | 0.012 | 0.949 | 0.010 | 0.909 | 0.033 | 0.964 | 0.000 | 0.956 | 0.000 |
Red | 0.954 | 0.015 | 0.943 | 0.022 | 0.901 | 0.045 | 1.061 | 0.001 | 0.961 | 0.000 |
NIR | 0.974 | 0.007 | 0.957 | 0.002 | 0.947 | 0.017 | 0.966 | 0.000 | 0.956 | 0.000 |
| Green | 0.956 | 0.008 | 0.959 | 0.007 | 0.901 | 0.017 | 0.965 | 0.000 | 0.957 | 0.000 |
Red | 0.962 | 0.013 | 0.964 | 0.009 | 0.905 | 0.022 | 1.102 | 0.000 | 0.964 | 0.000 |
NIR | 0.952 | 0.006 | 0.951 | 0.008 | 0.924 | 0.017 | 0.965 | 0.000 | 0.955 | 0.001 |
| Green | 0.940 | 0.010 | 0.942 | 0.007 | 0.915 | 0.015 | 0.950 | 0.002 | 0.939 | 0.003 |
Red | 0.938 | 0.013 | 0.935 | 0.018 | 0.913 | 0.019 | 1.091 | 0.003 | 0.944 | 0.003 |
NIR | 0.961 | 0.007 | 0.945 | 0.006 | 0.942 | 0.019 | 0.955 | 0.002 | 0.941 | 0.003 |
| Green | 0.928 | 0.015 | 0.940 | 0.009 | 0.925 | 0.015 | 0.951 | 0.006 | 0.939 | 0.007 |
Red | 0.923 | 0.016 | 0.942 | 0.009 | 0.921 | 0.016 | 1.124 | 0.006 | 0.945 | 0.006 |
NIR | 0.961 | 0.011 | 0.944 | 0.007 | 0.960 | 0.011 | 0.955 | 0.005 | 0.941 | 0.007 |