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The shipborne INS used in the sea test is the egm20088 as in [ 6 ], where the specifications of the instruments are described in detail. When the compensation error is required to be no more than 1 arc-second, it is recommended that the single-point DOV should be computed within 1 s and updated at an interval less than s for marine navigation, and 20 s for airborne INSs.

The proposed refinement method improved the SPM consistencies from 0. Gravity Disturbance Vector and Its Induced Position Errors The accelerometer sensed specific force vector egm208 is the combination of the kinematic acceleration vector a and the gravitational acceleration vector Gas: Filenames containing a ". According to our previous experiences, usage of the first or second degree polynomial functions can be sufficient egm20008 practice.

In the high-precision and long-term INSs with both the altitude damping and the horizontal velocity damping networks, the gravity disturbance vector induced errors exist almost exclusively in the horizontal channels and are mostly caused by the DOV. Statistic models can be used not only to analyze the error propagation of unknown gravity, but also for optimal prediction and filtering of the gravity disturbance in INSs [ 5 ], airborne gravimetry [ 8 ] and precise orbit determination for Earth-orbiting satellites [ 9 ].

The accelerometer sensed specific force vector f is the combination of the kinematic acceleration vector a and the gravitational acceleration vector Gas:.

### NGA: EGM - WGS 84 Version

Self-Consistent statistical models for the gravity anomaly, vertical deflections, and undulation of the geoid. Modified multiquadric methods for scattered data interpolation over a sphere, Ehm2008 Aided Design7, Along this route several symmetrically distributed peaks can be observed in the original position errors, which implies some kind of relevance with the local underwater topography. This is an important advantage. Journal List Sensors Basel v.

From the Bode plot it can be concluded egk2008 the gravity disturbance vector induced latitude and longitude errors consist of two parts. Moreover, the fluctuations in the DOV excite Schuler oscillation since the system is underdamped.

Thus gravitational information along the route plays an important role to extract the kinematic acceleration of the vehicle first. In this section, the accuracy of EGM model was tested at regional and local level in terms of performance of each improved eg2m008. For example, when truncating the model at degreethe differences become 2.

## Gravity Compensation Using EGM2008 for High-Precision Long-Term Inertial Navigation Systems

The discrepancies in geoid heights were calculated for CSF model. Open in a separate window.

Accuracy assessment of the available geoid models in Algeria. This will be discussed in detail in the next section. After optimizing the layout of spherical harmonic coefficients, the average single-point computing time has been reduced greatly to less than 1 s, which makes it possible to implement the second method for real-time gravity compensation applications.

Results and Discussion 6. A number of researchers have used the covariance propagation analysis to theoretically investigate the gravity induced navigation errors as early as the second half of the 20th century. Firstly, a trend surface is fitted to the application of method by using control points.

It should be noted that the results about truncation in this section are gained over the mid-latitude areas. First, the error propagation of the gravity disturbance vector in such systems is analyzed and two methods for gravity compensation using the EGM are provided.

Published online Dec And if the calculation time is under 1 s, an update interval of 20 s can ensure the compensation error less than 1 arc-second, as what the marker shows in Figure 5.

How to cite this article. Several theoretical works and simulations indicated that the gradiometer would help improve the navigation performance with in situ measurements of the gravity field [ 1112 ], yet the high cost still limits its application in comparison to accurate high-resolution data archives. For other applications, the previous release of the full 'Geoscience' package for EGM can be accessed through rgm2008 link at the bottom of this web page. As the errors of free-inertial navigation diverge over time, most INSs utilize a kind of feedback loop with external altitude and velocity references to restrain the divergence in the vertical ebm2008 and the Schuler oscillation in the horizontal channels, namely the damping network.

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