@abc.abstractmethod<EOL><INDENT>def get_uncertainty_minus(self):<DEDENT>
return<EOL>
Gets the uncertainty in the negtive direction for each value of this heading.

        The size of the returned array is typically one less than
        ``getDimensions()``.

        :return: the negative uncertainty values
        :rtype: ``decimal``


        *compliance: mandatory -- This method must be implemented.*