Pickup of terrain point coordinate based on geometric method

Aiming at the problem of interactive pickup of terrain point's accurate coordinate, the pickup strategy of terrain point coordinate based on geometric method was proposed. The strategy used the intersecting geometric ray and sphere, and designed the dichotomy of spherical center's angle which searched the accurate terrain point's coordinate according to DEM spatial information. The experimental results showed that the strategy not only got the accurate coordinates of the intersection of terrain,but also increasesd interactive operating fluency in virtual reality geographic system,and it provided a new approach for studying the theory of generating interactively curve on Earth.