Improvement of air navigation support of the landing phase by optimizing the allocation of pseudolites GLONASS
The article is devoted to the problem of the rational quality definition of the GLONASS system pseudo satellites and to the problem of optimization of their location relating to the runway for supplying better accuracy of the aircraft positioning on the final landing stage. The article presents the optimization criterion based on the minimization of the vertical geometrical factor both in a pre-set point and lengthwise the glide path. The difficulty in solving the problem is in a constant change of a geometrical factor due to the satellite moving relating to a user. The problem of optimization has been solved during a period of time which is equal to a period of orbital movement satellites GLONASS frequency with an hour discreteness. In this case we get a set of pseudo satellites locations which are optimal for a certain chosen moment of time. The method of finding the only positioning of pseudo satellites among others offered is based on the creation of the histogram of the latitude and longitude coordinates. To define the optimal pseudo satellites location, certain algorithms are drawn up which are based on the method of a direct search ( by Hook-Jeeves) and a no rigid polygon (by Nelder-Mid). The comparison of results got by both methods proved the adequacy of found solutions. To conduct the research a program complex LabView was created. It has got the module of orbital movement GLONASS imitation which works on the base of the functioning almanac of the system. The data out of this almanac are the characteristics of a nautical session in a set point of any pre-set period of time. And the data out of the optimization module that implements certain algorithms are the coordinates of optimal position pseudolites points. On the bases of the carried research there is a benefit in the average value of geometric factor both lengthwise the glide path and certain points provided in case of the pseudolites optimal position. The Influence of the number of optimal position pseudolites on the vertical geometric factor value in a zone of the airdrome was researched. It was proved that for the vertical geometric factor minimization and the zone increase, within provided minimum value, the use of more than three pseudolites is not rational.