A vertical integrity monitoring method and system are described. The vertical integrity monitoring method includes determining a noise sigma ratio parameter. The method also includes determining two vertical protection limit slopes and an associated covariance matrix. The method further includes determining a vertical integrity limit and set of weights based on the VPL slopes, covariance and the parameter; and applying the set of weights based on the parameter to calculate a vertical solution. An integrity monitoring system may have hardware and/or software embodying the one or more methods described.