Navigation system, display changeover method, and display device

Navigation systems, display changeover methods and programs, and display devices display an image, detect a turn amount and a turn direction, and scroll the displayed image based on the detected turn amount and the detected turn direction. The navigation systems, display changeover methods and programs, and display devices determine whether the detected turn amount is at least a predetermined turn amount in one direction within a preset period and continuously scroll the displayed image in the detected turn direction when the detected turn amount is at least the predetermined turn amount in the one direction within the preset period.