Generate DBH Inversion Model

Function Overview

Generate DBH Inversion Model builds a DBH inversion model from tree height, crown width, and measured DBH in an individual tree attribute file. The tool supports multiple empirical formulas and nonlinear fitting methods, solves model parameters by least squares, and saves the model as a .dbhim file for DBH Inversion.

Usage

Click User Plugins > Generate DBH Inversion Model to open the tool.

Steps

  1. Select a .treedb file that contains tree height, crown width, and DBH fields in Individual Tree Attribute File.
  2. Select the DBH inversion formula in Formula Selection.
  3. Set Output Path to save the generated DBH inversion model file and log file.
  4. Click OK to start fitting. The tool reads valid samples, extracts tree height, crown width, and DBH, and solves model parameters according to the selected formula.
  5. After fitting, a .dbhim model file and fitting log are generated in the output path.

Parameter Settings

  • Individual Tree Attribute File: .treedb file used to train the model. The file must contain tree height, crown width, and DBH fields.

  • Formula Selection: Formula used to build the DBH inversion model. Linear, logarithmic, exponential, power function, Logistic, and NLME forms are supported.

  • Output Path: Save location of the model file and log file. The model file is named in the format DBHInversion_model_formulaID_timestamp.dbhim.

Supported Formulas

The following formulas are supported. D represents DBH, H represents tree height, and CW represents crown width.

  1. D = a * CW + b * H + c
  2. ln(D) = a + b * ln(H)
  3. ln(D) = a + b * ln(CW)
  4. ln(D) = a + b * ln(H * CW)
  5. ln(D) = a + b * ln(H) + c * ln(CW)
  6. ln(D) = a + b * CW
  7. D = a + b * CW
  8. D = a + CW^b
  9. D = a * ln(CW) + b
  10. D = a + b*CW + c*CW*CW
  11. D = a*CW*CW + b*CW + c*H + d*H*H + e*CW*H + f
  12. D = a / (1 + b*exp(-(c*H + d*CW)))
  13. D = a * exp(b*H + c*CW)
  14. D = a * H^b * CW^c
  15. D = a * H^b * CW^c + d
  16. D = a * H^b * CW^c + u_i

Output

  • DBH Inversion Model File: .dbhim file that stores the model formula, fitted coefficients, sample count, and accuracy statistics.

  • Log File: Records input data, selected formula, sample statistics, fitted coefficients, complete formula, and model accuracy.

Accuracy Metrics

The generated model records the following statistics:

  • R-squared: Coefficient of determination used to evaluate goodness of fit.
  • RMSE: Root mean square error.
  • MAE: Mean absolute error.
  • n_samples: Number of valid samples used for fitting.

Notes

  • Tree height, crown width, and DBH in the individual tree attribute file must be valid positive values. Non-positive or invalid values are not used for fitting.
  • Different formulas are suitable for different stand and sample conditions. Select a model according to sample size, tree species, and fitting accuracy.
  • The generated .dbhim file can be used directly by the DBH Inversion tool.

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