Sufficient conditions for accuratefestlmation of a nonlinear process

A local condition is discussed for complete observability of nonlinear continuous processes with smooth functions. For two specific estimation algorithms, conditions are studied which, with infinite decrease of the measurement noise level, help infinite increase of the estimating accuracy (conditions for accurate estimation). Use of time derivatives as well as of the quantity is shown to make the condition for accurate estimation practically coincide with that for complete observability.