In an information processing method, an orientation sensor is mounted on a targeted object to be measured, and bird's-eye view cameras for capturing images of the targeted object are fixedly installed. From the images captured by the bird's-eye view cameras, an index detecting unit detects indices mounted on the orientation sensor. A measured orientation value from the orientation sensor is input to an orientation predicting unit, and the orientation predicting unit predicts the present orientation of the targeted object based on an azimuth-drift-error correction value. A position-orientation calculating unit uses the image coordinates of the detected indices to calculate the position of the imaging device and an update value of the azimuth-drift-error correction value, which are unknown parameters. From the obtained parameters, the position-orientation calculating unit finds and outputs the position and orientation of the targeted object.