The partial outcome of the signal processing consists of the distances to the GPs satellites through the digital codes(known as the pseudoranges) and the satellitecoordinates through the navigation message. Theoretical only three distances to threesimultaneously tracked sat- elites are needed. In this case, the receiver would be located at the intersec- tion of three spheres each has a radius one receiver-satellite distance and on that particular satellite(Figure l.5). From the practical of point view, however, a fourth satellite is needed to account for the receive clock offset[6]. details on this are given in Chapter 5. The accuracy obtained with the method described earlier was until recently limited to 100m for the horizontal component, 156m for the verti and ns for the time component, all at the ability level. This low accuracy level was due to the effect of the so-called selective availability, a technique used to intentionally degrade the autono recent real-time positioning accuracy to unauthorized users[3l.
The partial outcome of the signal processing consists of the distances to the GPs satellites through the digital codes(known as the pseudoranges) and the satellitecoordinates through the navigation message. Theoretical only three distances to threesimultaneously tracked sat- elites are needed. In this case, the receiver would be located at the intersec- tion of three spheres each has a radius one receiver-satellite distance and on that particular satellite(Figure l.5). From the practical of point view, however, a fourth satellite is needed to account for the receive clock offset[6]. details on this are given in Chapter 5. The accuracy obtained with the method described earlier was until recently limited to 100m for the horizontal component, 156m for the verti and ns for the time component, all at the ability level. This low accuracy level was due to the effect of the so-called selective availability, a technique used to intentionally degrade the autono recent real-time positioning accuracy to unauthorized users[3l.
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