Table 3. The best fitted VI-LAI relationships and their statistics.
Study areas | VI | VI = VI ∞−(VI ∞−VI g)exp(−KVILAI) | STDV | (VI max−VI min) | R 2 | RMSE | Normalized RMSE |
Tiantongshan | NDVI | y = 1–0.354exp(−0.11x) | 0.025 | 0.090 | 0.3703 | 0.0205 | 0.2278 |
SAVI | y = 1–0.7837exp(−0.064x) | 0.048 | 0.180 | 0.2600 | 0.0431 | 0.2389 | |
OSAVI | y = 1–0.672exp(−0.0619x) | 0.035 | 0.128 | 0.3291 | 0.0305 | 0.2381 | |
MSAVI | y = 1–0.8693exp(−0.078x) | 0.061 | 0.231 | 0.2571 | 0.0549 | 0.2380 | |
RSR | y = 10.5–10.5exp(−0.237x) | 0.990 | 3.424 | 0.3648 | 0.8274 | 0.2417 | |
MNDVI | y = 0.7299–0.2589exp(−0.2271x) | 0.042 | 0.151 | 0.0879 | 0.0425 | 0.2806 | |
MAVI | y = 1–0.6268exp(−0.067x) | 0.024 | 0.091 | 0.6975 | 0.0137 | 0.1501 | |
Maoershan | NDVI | y = 1–0.4002exp(−0.1724x) | 0.068 | 0.224 | 0.5338 | 0.0487 | 0.2171 |
SAVI | y = 1–0.6835exp(−0.0703x) | 0.082 | 0.275 | 0.3902 | 0.0674 | 0.2454 | |
OSAVI | y = 1–0.6115exp(−0.0715x) | 0.070 | 0.225 | 0.4409 | 0.0546 | 0.2423 | |
MSAVI | y = 1–0.7391exp(−0.0901x) | 0.108 | 0.363 | 0.3802 | 0.0893 | 0.2459 | |
RSR | y = 11–11exp(−0.222x) | 2.022 | 7.143 | 0.7580 | 1.0435 | 0.1461 | |
MNDVI | y = 0.6052–0.6052exp(−0.5351x) | 0.101 | 0.360 | 0.6281 | 0.0644 | 0.1789 | |
MAVI | y = 0.6904–0.4266exp(−0.3107x) | 0.068 | 0.238 | 0.7417 | 0.0361 | 0.1517 | |
Hulunbeier | NDVI | y = 0.8482–0.4956exp(−0.5686x) | 0.086 | 0.398 | 0.6667 | 0.0505 | 0.1269 |
SAVI | y = 1–0.7754exp(−0.0978x) | 0.056 | 0.274 | 0.6496 | 0.0340 | 0.1239 | |
OSAVI | y = 0.776–0.5105exp(−0.196x) | 0.060 | 0.291 | 0.6622 | 0.0357 | 0.1228 | |
MSAVI | y = 1–0.8206exp(−0.1041x) | 0.063 | 0.309 | 0.6382 | 0.0389 | 0.1258 | |
RSR | y = 9–9exp(−0.1739x) | 1.234 | 5.927 | 0.6386 | 0.7569 | 0.1277 | |
MNDVI | y = 0.5713–0.5713exp(−0.3985x) | 0.100 | 0.424 | 0.6449 | 0.0607 | 0.1430 | |
MAVI | y = 0.7205–0.5394exp(−0.2354x) | 0.069 | 0.332 | 0.6924 | 0.0391 | 0.1176 | |
Xilinhaote | NDVI | y = 1–0.7552exp(−0.2631x) | 0.120 | 0.503 | 0.6647 | 0.0712 | 0.1415 |
SAVI | y = 1–0.8425exp(−0.0936x) | 0.078 | 0.348 | 0.5071 | 0.0562 | 0.1615 | |
OSAVI | y = 1–0.8181exp(−0.1163x) | 0.083 | 0.366 | 0.5923 | 0.0541 | 0.1479 | |
MSAVI | y = 1–0.8784exp(−0.0957x) | 0.086 | 0.386 | 0.4741 | 0.0640 | 0.1658 | |
RSR | y = 12.5–12.5exp(−0.1579x) | 1.995 | 9.297 | 0.6669 | 1.1749 | 0.1264 | |
MNDVI | y = 0.825–0.825exp(−0.4007x) | 0.186 | 0.691 | 0.6858 | 0.1065 | 0.1541 | |
MAVI | y = 1–0.8952exp(−0.1275x) | 0.092 | 0.384 | 0.6627 | 0.0544 | 0.1418 |
Note: STDV is the standard deviation of each VI corresponding to the whole range of measured LAI. (VI max–VI min) is the difference between the maximum and minimum value of each VI corresponding to the whole range of measured LAI. The last column gives the normalized RMSE (i.e., RMSE/(VI max–VI min)) for each VI. Values in bold font indicate high performance.