Aiming at the incomplete metrical information of target under special condition of battlefield,a novel processing idea with the elevation-only parameter is proposed,and a filtering algorithm of parametric trajectory of special target with projection rules is designed.By using Stewart Theorem and Total Least Square Algorithm,the elevation-only filter algorithm is discussed which is under the condition of constant altitude flight and diagonal line flight.The simulation results show that the new algorithm achieves a favorable filtering precision,which can be used under the special condition with incomplete metrical information.