Quality and geometry strength of object point positioning by means of ADS40 photographic intersection

In this paper, simulated data and real ADS40 images are adopted for evaluating the quality (accuracy and reliability) and geometry strength (condition number) of object point positioning by means of photographic intersection using conjugate rays in ADS40 images. Tests by using simulated data show that three-ray intersection in a single ADS40 strip provides the horizontal and vertical accuracy of 0.25 and 0.55 pixels, respectively. For the nine-ray intersection in three parallel strips, the horizontal and vertical accuracy is 0.14 pixels and 0.19 pixels, which is increased by 44% and 65% respectively. Tests of real ADS40 images show the horizontal and vertical accuracy on the images is about 0.5 and 0.6 pixels, respectively. The more conjugate rays, the better the accuracy and reliability. Moreover, the optimal angle between forward and nadir direction is 24°, which is close to the angle adopted currently by the ADS40 (26°).