| 摘要 |
<p>A first position of a GNSS satellite is calculated at a first time on the basis of orbit data corresponding to an orbit path of the satellite received from the satellite. An orbit path of the satellite from the first position at the first time to a second time is modelled (predicted) using Kepler equations to determine a second position of the satellite at the second time, taking into account solar wind, the gravitational effects of the sun and moon, etc. A third position of the satellite at the second time is calculated in dependence on further received orbit data, and the difference between the second and third positions is compared to a threshold to determine the validity of the orbit data. Thus spoof data can be rejected. The system may be used in tracking arrangements, for instance to locate stolen vehicles, automatic tolling, or emergency reporting.</p> |
