def get_longitudinal_extent(lon1, lon2):
    """
    Return the distance between two longitude values as an angular measure.
    Parameters represent two longitude values in degrees.

    :return:
        Float, the angle between ``lon1`` and ``lon2`` in degrees. Value
        is positive if ``lon2`` is on the east from ``lon1`` and negative
        otherwise. Absolute value of the result doesn't exceed 180 for
        valid parameters values.
    """
    return (lon2 - lon1 + 180) % 360 - 180