Based On The Astronomical Level Of Gps Inter-obstacle Elevation Pass

The height transfer across obstacle with long-distance and high precision is one of difficulties in engineering survey all the time. The main trouble of traditional methods is low resolving power of distant measurement. With the distance across obstacle increasing, the accuracy becomes lower and lower. If the distance is over 10 kilometers, all the traditional methods are invalid.One of advantages GPS possessing is distant measuring without intervisibility, so GPS has a potential to solve the above problem. The sixty-four-dollar question is that the height datum in both sides of obstacle is not consistent. Even they belong to the same height system, their datum should be treated inconsistent. Consequently the general geometrical fitting method can not be used directly. A new method in this paper is offered to solve the question, which is based on astronomical leveling and uses GPS to measure height anomaly difference between both sides of obstacle.As everyone knows, the nature of GPS leveling is to fit shape of local quasi geoid. The key value corresponding to shape of quasi geoid is surface deflection of the vertical. It approximatively can be looked upon as spatial angle between quasi geoid's normal and ellipsoidal normal. For the certain ellipsoid, surface deflection is only related to the shape of quasi geoid, not to absolute position. In other words, deflection of the vertical is not affected by the height datum. Accordingly we can design a new method, in which we firstly use GPS leveling to fit shape of local quasi geoid in both sides of obstacle, secondly determine surface deflections which are belonged to WGS-84, in the end adopt principle of astronomical leveling and isostasy to compute height anomaly difference between both sides of obstacle. The above is basic thought of the new method.From the above thought, the study of this paper is divided five sections. The first one is to deduce the rigor relation between height anomaly difference and surface deflection from Stocks's concept and Molodenskij's concept. The second one studies how to use GPS leveling to measure surface deflection of the vertical. The third one studies how to put GPS astronomical leveling in practice. The forth one studies how to put GPS astro-isostatic leveling in practice, which is based on astro-gravimetric leveling and isostasy and in order to improve range and accuracy. The fifth one is to initially test practical accuracy of the new method combined instances.