bn	Ratio of volumetric heat capacity of the cable with volumetric heat capacity of the soil (–)
c	Specific heat capacity of the soil (J kg−1 K−1)
cs	Soil solid specific heat capacity (J kg−1 K−1)
cw	Specific heat capacity of water (J kg−1 K−1)
Cs	Volumetric heat capacity of the soil (J m−3 K−1)
C 1	Heat capacity of the heating cable (J m−3 K−1)
C 2	Heat capacity of the sensing cable (J m−3 K−1)
p	Transform variable of the Laplace transform
vf	Transfer function
K 0	Modified Bessel function of the second kind of order 0
K 1	Modified Bessel function of the second kind of order 1
L	Distance between the two centers of the cables (m)
Lapp	Apparent spacing between the two centers of the cables (m)
q	Power released per unit length cable (W m−1)
r 1	Cable radius of the heating cable (m)
r 2	Cable radius of the sensing cable (m)
t 0	Heating time (s)
teval	Evaluation time for regression approach (s)
Tmax	Temperature amplitude at the sensor cable (K)
tmax	Time of tmax after heating has started (s)
Γ1(t)	Heating function at the heater cable
Γ2(t)	Heating function at the sensor cable
ϴ	Volumetric water content (m3 m−3)
κ	Thermal diffusivity (m2 s−1)
λs	Thermal conductivity of the soil (W m−1 K−1)
ρd	Soil bulk density (kg m−3)