Evaluation of the Confidence Intervals

This chapter describes the methods of evaluation of the confidence interval of the estimated position (the PL), taking into account the remaining errors, which may be present in the measured pseudoranges, after the application of the FD and FDE algorithms. We have seen in the previous chapter that these algorithms are able to exclude undesired situations. The position is generally considered unavailable if the FD detects unacceptable faults, and then in this case it is not necessary to evaluate the confidence interval, since there is not an estimated position. If the faulty satellites are excluded by the FDE algorithm, the position is accepted, and the confidence interval has to be evaluated. However undetectable errors still remain in the estimated position and they have to be taken into account in the PL computation.