2015 年 35 巻 3 号 p. 155-172
We can quickly grasp the information of land surface by aerial images. In particular, if the aerial images are integrated with GIS, these images can be used for various purposes. Therefore, the aerial image registration to a map is quite important. For this purpose, GPS/IMU is used in recent years, however all aircraft are not equipped with it.
When a wide-scale disaster strikes, if aerial images taken by any ordinary cameras without IMU can be used to the registration to maps, lots of aircrafts can be used to collect the land surface situation linked with geographical information. However, the image based registration between the aerial image and the map is not simple. This is because an aerial image taken by the hand-carried camera will be an oblique aerial image with perspective distortion, and not all objects in the map are in the aerial image, and vice versa. Furthermore, the position of the reference point in the oblique aerial image is different from aircraft’s position measured by GPS.
In this paper, we propose an automatic registration method for the oblique aerial image. The IMU is a special device, but GPS is general. Our method uses an oblique aerial movie with GPS data. The method consists of three parts: estimation of major directions at Pseudo-orthogonal image, estimation of the location of the reference point, and estimation error removal by using a digital map image. We implemented our proposed method on a personal computer, and experimented using real data. As a result, the maximum error on the road areas is within six meters, and the results show that the proposed method is useful for several operations after the disasters.