Superimposed-image display device and computer program

A superimposed image display device that is mounted on a vehicle and that displays a guide image such that the guide image is superimposed on a view ahead of the vehicle and is visually recognized, the guide image providing guidance of information to a driver of the vehicle, the superimposed image display device comprising:

• a processor programmed to:
• obtain three-dimensional map information that specifies a three-dimensional shape of a road and a structure nearby the road;
• obtain a captured image that captures a view ahead of the vehicle;
• compare the captured image and the three-dimensional map information at prescribed intervals, the prescribed interval is an interval where a comparison is done each time a structure having a distinctive shape, which can be easily compared, is included in the captured image;
• specify a position of the driver in the three-dimensional map information, based on a result of the comparison;
• estimate the position of the driver in the three-dimensional map information, during a time between timings at which the comparison is performed;
• specify as the position of the driver in the three-dimensional map information, the estimated position of the driver during the time between timings at which the comparison is performed;
• arrange the guide image in the three-dimensional map information, based on the three-dimensional shape of the road and the structure nearby the road;
• obtain a shape of the guide image that is visually recognized from the position of the driver in the three-dimensional map information;
• and
• display the guide image having the obtained shape.