def calc_relative_density_boulanger_et_al_2014_cpt_values(q_c1n, c_dq=0.9):
    """
    Table 4.1 in PM4Sand v3.1 manual

    Parameters
    ----------
    q_c1n: array_like
        Normalised cone penetration resistance
    c_dq: float, default=0.9 (from :cite:`Idriss:2008ua`)
        Correlation factor, (range 0.64-155 from Salgado (1997)

    Returns
    -------
    array_like
    """
    return 0.465 * (q_c1n / c_dq) ** 0.264 - 1.063
