1. A method for estimating a position of a target by using an image acquired from a camera, comprising the steps of: (a) setting multiple virtual estimated reference points by dividing a view-path, as a virtual straight path from a geoid to the camera, where the target is located, into a natural number which is 2 or higher number; (b) comparing altitude values of the respective estimated reference points existing between O (x 0 , y 0 , z 0 ) as a point where the view-path and the geoid intersect and C (x n , y n , z n ) as a position of the camera with those of respective points on terrain corresponding to the respective estimated reference points; (c) searching neighboring virtual estimated reference points P k (x k , y k , z k ) and P k+1 (x k+1 , y k+1 , z k+1 ) among the multiple virtual estimated reference points to satisfy a requirement under which a difference between an altitude z k of one point P k (x k , y k , z k ) among the neighboring estimated reference points and that of the terrain corresponding thereto and a difference between an altitude z k+1 of the other point P k+1 (x k+1 , y k+1 , z k+1 ) among the neighboring estimated reference points and that of the terrain corresponding thereto have different signs; and (d) determining that the actual position of the target exists between the searched estimated reference points P k (x k , y k , z k ) and P k+1 (x k+1 , y k+1 , z k+1 ).