Abstract
A new method for dynamic measurement of deflections of the vertical (DOV) is proposed in this paper. The integration of an inertial navigation system (INS) and global navigation satellite system (GNSS) is constructed to measure the body's attitude with respect to the astronomical coordinates. Simultaneously, the attitude with respect to the geodetic coordinates is initially measured by a star sensor under quasi-static condition and then maintained by the laser gyroscope unit (LGU), which is composed of three gyroscopes in the INS, when the vehicle travels along survey lines. Deflections of the vertical are calculated by using the difference between the attitudes with respect to the geodetic coordinates and astronomical coordinates. Moreover, an algorithm for removing the trend error of the vertical deflections is developed with the aid of Earth Gravitational Model 2008 (EGM2008). In comparison with traditional methods, the new method required less accurate GNSS, because the dynamic acceleration calculation is avoided. The errors of inertial sensors are well resolved in the INS/GNSS integration, which is implemented by a Rauch–Tung–Striebel (RTS) smoother. In addition, a single-axis indexed INS is adopted to improve the observability of the system errors and to restrain the inertial sensor errors. The proposed method is validated by Monte Carlo simulations. The results show that deflections of the vertical can achieve a precision of better than 1″ for a single survey line. The proposed method can be applied to a gravimetry system based on a ground vehicle or ship with a speed lower than 25 m/s.
Highlights
High resolution and high precision gravity data are desirable in many applications, such as geodesy, solid earth geophysics and resource exploration
In order to overcome these disadvantages of the star sensor, we propose to use laser gyroscope unit (LGU) to maintain the attitude reference obtained by the star sensor
A new method for the dynamic measurement of deflections of the vertical (DOV) is proposed in this paper based on an inertial navigation system (INS)/global navigation satellite system (GNSS) integration system and a star sensor
Summary
High resolution and high precision gravity data are desirable in many applications, such as geodesy, solid earth geophysics and resource exploration. In comparison with the scalar gravimetry, the vector gravimetry based on the GNSS/INS integration is more challenging, and it can measure all three components of gravity disturbances under dynamic conditions. The gravity disturbances are calculated by the difference between the GNSS-derived accelerations and INS-sensed specific force in the absence of any gravity stochastic models This kind of method has been greatly improved and widely adopted by many vector gravimetry systems in the last two decades. A single-axis indexed inertial navigation system is adopted to enhance the observability of the system errors and restrain the bias errors of the inertial sensors Because of these three features, the errors of attitude reference, GNSS and INS will be well handled, respectively.
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