This paper describes an optimal guidance policy for a vehicle to reach a relative position to a target, using information from a single fixed camera. Applying an extended Kalman filtering method, both of a velocity and a position of the vehicle relative to the target, can be estimated. However, estimates of a distance between the vehicle and the target are much worse than those of the other states. Therefore, in this paper, an optimal guidance policy is introduced that can reach the destination while maximizing the predicted accuracy of the range estimation. By limiting vehicle motion to a two dimensionals, the exact solution for control inputs for this optimization problem can be obtained. Simulation results show that the resulting optimal guidance policy gives far more accurate range estimation than a simple linear guidance policy.