def get_geometries(type='HB'):
    """
    Function to return typical geometries for different aquicistions.

    Parameters
    ----------
    type : {'HB', 'HF', 'VB', 'VF'}
        Backscatter type:
            * HB: Horizontal Back Scattering (90.0, 90.0, 0.0, 180.0, 0.0, 0.0).
            * HF: Horizontal Forward Scattering (90.0, 90.0, 0.0, 0.0, 0.0, 0.0).
            * VB: Vertical Back Scattering (0.0, 180.0, 0.0, 0.0, 0.0, 0.0).
            * VF: Vertical Forward Scattering (180.0, 180.0, 0.0, 0.0, 0.0, 0.0).

    Returns
    -------
    geometry : tuple
        A tuple with (iza, vza, iaa, vaa, alpha, beta) parameters.

    """
    if type is 'HB':
        return 90.0, 90.0, 0.0, 180.0, 0.0, 0.0
    elif type is 'HF':
        return 90.0, 90.0, 0.0, 0.0, 0.0, 0.0
    elif type is 'VB':
        return 0.0, 180.0, 0.0, 0.0, 0.0, 0.0
    elif type is 'VF':
        return 180.0, 180.0, 0.0, 0.0, 0.0, 0.0
    else:
        raise ValueError(
            "The parameter type should be 'HB', 'HF', 'VB', 'VF'. The actual parameter is: {0}"
            .format(str(type)))
