def _ivc_to_model_input(ivc, actual_yield, burst_height):
    """This function converts an International Visibility Code [1-9] into the numbers used in the Soviet thermal impulse model."""
    if ivc == 9:
        return 1
    else:
        groundburst = 10 - ivc
        if ivc == 3 or ivc == 2:
            groundburst = groundburst + 1
        if burst_height == 0 or actual_yield <= 100:
            return groundburst
        else:
            return groundburst - 1