Model/phase

RMSE (ppt)

MAE (ppt)

CC

BPNN/training

3.88

2.79

0.76

RBFNN/training

3.76

2.72

0.77

Three-dimensional model/calibration

4.49

3.80

0.79

BPNN/verification

3.81

2.96

0.71

RBFNN/verification

3.63

2.90

0.75

Three-dimensional model/verification

5.09

4.25

0.75