Similarly to the first test, 15 sets of targets were placed symmetrically along the road, however, for this test, the targets were placed closer to each other with varying density ; in the middle of the strip the average distance was about 130 m between two sets of targets, while towards the ends, 450 m, and 950 m as shown in the figure 10. to provide control coordinates, the targets were gps surveyed with a horizontal accuracy of 1-2 cm, and a vertical accuracy of about 2-3 cm.