Table 3.

Performance comparison of factory and own calibrations for two-point calibration approach of ThetaProbe: R² values, average AD (vol %), and RMSE values (vol %).

Calibration Type	Tested Material	Packing	R2	Average AD (vol %)	RMSE (vol %)
Linear factory	Soil	Moderate	0.953	1.88	2.32
Polynomial factory	Soil	Moderate	0.949	1.89	2.45
Linear own	Soil	Moderate	0.953	2.05	2.42
Polynomial own	Soil	Moderate	0.949	2.03	2.36
Linear factory	Sand	Loose	0.982	4.51	4.73
Polynomial factory	Sand	Loose	0.991	3.40	3.61
Linear own	Sand	Loose	0.982	6.17	9.06
Polynomial own	Sand	Loose	0.991	4.98	7.08
Linear factory	Sand	Moderate	0.998	2.64	2.95
Polynomial factory	Sand	Moderate	0.999	1.77	1.91
Linear own	Sand	Moderate	0.998	3.64	4.89
Polynomial own	Sand	Moderate	0.999	2.34	3.14
Linear factory	Sand	Compact	0.990	2.35	2.17
Polynomial factory	Sand	Compact	0.995	1.21	1.16
Linear own	Sand	Compact	0.990	3.01	2.78
Polynomial own	Sand	Compact	0.995	1.36	1.36