A method for determining overbounds comprises the steps of determining conservative overbounds (qi) of at least one error (εi) in a first phase space, multiplying the conservative overbounds (qi) of errors (εi) in the first phase space by a first parameter (θ(−x)·2) and a second parameter (θ(x)·2), and determining an upper bound for the integrity risk at the alert limit (pw,int(AL)) in a second phase space using overbounds (qi) of errors (εi) in the first phase space by the first parameter (θ(−x)·2) and the second parameter (θ(x)·2).