Calculation of the Intensity of C12 in covariance matrix [C3]

I am using the PolSARpro to process PolSAR datasets. The covariance matrix [C3] was extracted by the polsarpro, and I want to calculate the intensity of ShhShv* (C12). I am confused with the following two equations:

  1. Intensity_C12 = C12_real * C12_real + C12_imag * C12_imag.

  2. Intensity_C12 = sqrt(C12_real * C12_real + C12_imag * C12_imag).
    Would you please help me to figure out this problem?
    Thank you very much!