PURPOSE: To provide a conversion method by which pictures of video, etc., taken by an aircraft in flight viewing forward are converted into downward- viewing video database in real time.

CONSTITUTION: This method is characterized in that an aircraft 42 flying over related geographical features 20 acquires inclining forward-viewing sequential video data, and a position of a moving body and its attitude of x, y, z, roll, pitch, and yaw are calculated whenever each frame is formed, to estimate an accurate position of the aircraft 42, and picture elements corresponding to the overlapping part 23 of adjacent frames each other. And, distances to picture elements corresponding to each frame are calculated. And, positions of x, y, and z to each picture element of each frame is decided, and height data and radial data of each picture element to each frame are processed by using only the radial data extracted from lower part of each frame to generate a visual field looking down from the above, and proper downward-viewing database is thereby generated to be used for a video generation system.