The Optimal Degree of Gravity Spherical Harmonic Model Calculation for Gravity Disturbance Compensation in Inertial Navigation

In recent years, the significant improvement of inertial navigation, leaves the gravity disturbance as the important factor which affects the accuracy of inertial navigation. This paper focus on the compensation for gravity disturbance with gravity spherical harmonic model, especially the optimal degree of gravity spherical harmonic model with which to calculate the gravity disturbance. The effect of gravity disturbance on inertial navigation is analysed based on the amplitude-frequency response characteristics of inertial navigation error differential equation, then the dominantly influential frequency band of gravity disturbance can be found which is the target of compensation. Combination the dominantly influential frequency band with the spatial resolution of the Earth’s gravity spherical harmonic model EGM2008 which is used to calculate the gravity disturbance, the optimal degree can be determined based on an algorithm proposed in this paper. Finally, shipborne inertial navigation experiment confirms the correctness and effectiveness of the proposed algorithm.

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Analysis of Deflection of Vertical Compensation for Inertial Navigation System

Mathematical Problems in Engineering ◽

10.1155/2020/1975672 ◽

2020 ◽

Vol 2020 ◽

pp. 1-15

Author(s):

Shiwen Hao ◽

Zhili Zhang ◽

Zhaofa Zhou ◽

Junyang Zhao ◽

Zhenjun Chang ◽

...

Keyword(s):

High Precision ◽

Spherical Harmonic ◽

Inertial Navigation System ◽

Inertial Navigation ◽

Harmonic Coefficient ◽

Calculation Error ◽

Harmonic Model ◽

Spherical Harmonic Coefficient ◽

Deflection Of Vertical ◽

Spherical Harmonic Model

With the development of high-precision inertial navigation systems, the deflection of vertical (DOV), gravity disturbance, is still one of the main error sources that restrict navigation accuracy. For the DOV compensation of the Strapdown Inertial Navigation System (SINS) problem, the influences of the calculation degree of the spherical harmonic coefficient and the calculation error of the DOV on the compensation effect were studied. Based on the SINS error model, the error propagation characteristics of the DOV in SINS were analyzed. In addition, the high-precision global gravity field spherical harmonic model EIGEN-6C4 was established and the influence comparative analysis of the calculation degree of the spherical harmonic coefficient on the DOV compensation of SINS in different regions was carried out. Besides, the influence of the calculation error of the DOV on the compensation was emphatically analyzed. Finally, the vehicle experiment verified the feasibility of compensation in SINS based on the gravity field spherical harmonic model. The simulation and experiment results show that it is necessary to consider the influence of the calculation degree and the calculation error of the DOV on the compensation for long-time high-precision SINS with the position accuracy of 0.3 nm/h, while the SINS with general requirements for position accuracy can ignore the impact.

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Retrieving lithospheric magnetisation distribution from magnetic field models

Geophysical Journal International ◽

10.1093/gji/ggz471 ◽

2019 ◽

Cited By ~ 1

Author(s):

V Lesur ◽

F Vervelidou

Keyword(s):

Magnetic Field ◽

Cost Function ◽

Spherical Harmonic ◽

Field Model ◽

Harmonic Model ◽

Whole Process ◽

Magnetic Field Model ◽

The Cost ◽

Spherical Harmonic Model ◽

The Magnetic Field

Summary We investigate to which extent the radially averaged magnetisation of the lithosphere can be recovered from the information content of a spherical harmonic model of the generated magnetic field when combined with few simple hypotheses. The results obtained show firstly that a hypothesis of magnetisation induced by a field of internal origin, even over a localised area, is not sufficient to recover uniquely the radially averaged magnetisation and, secondly, that this magnetisation can be recovered when a constant magnetisation direction is assumed. An algorithm to recover the magnetisation direction and distribution is then described and tested over a synthetic example. It requires to introduce a cost function that vanishes when estimated in a system of coordinates with its Z axis aligned with the magnetisation direction. Failing to find a vanishingly small value for the cost function is an indication that a constant magnetisation direction is not a valid hypothesis for the studied magnetic field model. The range of magnetisation directions that are compatible with the magnetic field model and a given noise level, can also be estimated. The whole process is illustrated by analysing a local, isolated maximum of the Martian magnetic field.

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