  Surface roughness and dielectric properties are crucial in characterizing
radar backscattering from bare soil surfaces. However, their estimation depends
on the surface size of the sampling profile, and the complex relative
permittivity is disturbed by different dielectric spectrum models. Hence, it is
desirable to know how the uncertainty associated with roughness and complex
relative permittivity propagates to radar backscattering coefficients. To
identify the extent to which the uncertainty propagates, we examined the
roughness sample variance and bias of complex relative permittivity. Then, we
evaluated the error of radar backscattering coefficients as a function of
incident angle, frequency, and polarization induced by each of the two
uncertainty sources and their coupling. The results help interpret the
discrepancy among model predictions and in-situ measurements and suggest a
minimum surface size to estimate the RMS height and correlation length to
confine the radar backscattering coefficients' error.
