1. A method for a measuring instrument comprising a position calculating circuit including a tracker and a servo system, an angle measuring system and an optical distance measuring system for sending out measuring beams including optical radiation for distance and angle measurements and for receiving reflected beams during measurement sessions, said angle measuring system being adapted to calculate target position data including at least horizontal and vertical angle between said measuring instrument and a target using said measuring beams and reflecting beams, the method comprising: using the measuring instrument to, obtain sets of target position data including at least horizontal and vertical angle between said measuring instrument and said at least one target in consecutive measurements during a measurement session; calculate a model describing a path of and/or a distance to said target based on at least one data set obtained at a preceding measurement, said model predicting positions of said target; estimate at least a present position of said target and/or at least a present distance to said target using said calculated model; check whether said target has been lost, and if said target has been lost during a period of time, determine that said estimated position of said target and/or said estimated distance to said target is to be used in a search for said target; and use, at initiation of a new measurement session, said estimated position of said target when searching for said target.