Table 4.
Own linear and third-order polynomial calibration equations for ThetaProbe (direct regression approach).
| Tested Material | Packing | Regression Type | Equation |
|---|---|---|---|
| Soil | Moderate | Linear | y = 49.734x − 5.672 |
| Soil | Moderate | Third-order polynomial | y = 360.14x3 − 596.55x2 + 355.24x − 52.53 |
| Sand | Loose | Linear | y = 41.925x + 1.329 |
| Sand | Loose | Third-order polynomial | y = 63.827x3 − 101.39x2 + 86.101x − 3.236 |
| Sand | Moderate | Linear | y = 43.703x − 0.421 |
| Sand | Moderate | Third-order polynomial | y = 43.165x3 − 59.145x2 + 66.790x − 2.788 |
| Sand | Compact | Linear | y = 45.577x − 1.886 |
| Sand | Compact | Third-order polynomial | y = 115.52x3 − 155.39x2 + 105.12x − 8.1418 |