Patent ID: 9322919
Filing Date: 2016-04-26
CPC Classification: G01S

Claim Text:
1. A satellite based augmentation system comprising: a threshold value calculation unit which calculates a monitor threshold value for determining whether or not a value of carrier to noise power density ratio (C/No) at a time when a pseudorange is measured on the basis of a signal from a GPS satellite is proper; and a pseudorange determination unit which determines whether or not the pseudorange is of proper accuracy, by comparing the C/No value with the monitor threshold value; wherein the satellite based augmentation system comprising a reliability computation unit which calculates and outputs reliability of the signal from the GPS satellite used for the measurement of the pseudorange when the pseudorange determination unit determined the C/No value to be smaller than the monitor threshold value; wherein the threshold value calculation unit calculates a frequency distribution of the C/No values with respect to a plurality of measured the pseudoranges, and calculates the monitor threshold value the monitor threshold value that a probability P_CN_min of the C/No value which takes frequency smaller than the monitor threshold value is equal to the sum of a missed-detection probability P_md_cno and a false alarm probability P_fa_cno, wherein the missed-detection probability P_md_cno is a probability of situations where the properness of the pseudorange cannot be determined owing to the standard deviation of measurement errors in the C/No values in the frequency distribution being small than the monitor threshold value; and the false alarm probability P_fa_cno is a probability of situations where the pseudorange is determined to be improper, in spite of its satisfying an accuracy required of the pseudorange, owing to the standard deviation of measurement errors in the C/No values in the frequency distribution being smaller than the monitor threshold value.