The borescope includes an insertion tube, a first image processor (304), a model store unit (306), a pose calculator (307), a second image processor (314), a navigation image calculator (310) and a display (220). The insertion tube includes a detection head (242) and at least one sensor (2465) for receiving signals in the insertion tube and generating sensed signals (316). The first image processor (304) is for calculating a first image (312) based on first image signals (311) captured by the detection head (242). The second image processor (314) is for adjusting the initial pose (317) calculated by the pose calculator (307) to a navigation pose (324) until a difference between the first image (312) and a second image (322) calculated based on the navigation pose (324) and a predetermined model (318) falls in an allowable range. The navigation image calculator (310) is for calculating a navigation image (325) based on the navigation pose (324) and the predetermined model (318). The display (220) is for showing the navigation image (325).
