We experimentally research linear polarization characteristics of various terrains at millimeter wave band for image interpretation. We measure and discuss the polarization phenomena, and consider as well the incident angle which also affects terrain radiometric temperature. An economic single-channel radiometer is used in measurements, and changes to the linear polarization are produced by manually rotating its waveguide. We demonstrate that the characteristic in polarization is a decisive advantage of terrain identification in ways beyond that which can be achieved using an intensity radiometer alone.