powdsfsdfer buses. dsfdsdsf these sfdsmeasurements artretree so-calleretretd retretertvirtual msdfsddfsdeasurements, as mentiretertretreteroneretd earlier. Thfe idea is to ufdsse this very dsretretretfaccurate information in order to enhance the accurfdsfdsfacy of the estimatefsdfsds. Aschmoneit treated fthose measurementsdf sfdfeparately from tfsdhefsdfdsf telemetered measdsfdsfurements and itmretreposed fthem as f consdsfdsftraidsfned minimization problretreterem was then sdsfoertlvedfsd by the method of Lagrange multipliers. The sf multipliers. The firdsfsdfdsfst order necessary conditionsdsf for the optifdsfmum states that derivatives of the Lagrangian with resdsfdsfpecertretret to x and λ musretretertert vanrtretish ∂L(x, fsdfsdfλ) ∂xdsfsd =fdsdfsdfsfsddfsf dsfdsdsfdsf−HT Rsdfsdf −1 [z − h(x)] + C T sdfds = 0 ∂L(x, λ) ∂λ gftghtr= cgdsgfx) = 0 By applying fNfdston’s metterthod to the above tretsystterem of retertretretnonlinear equtreteratio