Apology

The article by Krzysztof Czaplewski, Sławomir Świerczyński and Piotr Zwolan entitled “Using elements of integral calculus in the process of optimizing the configuration of navigation positioning systems”3 published in the previous issue (45/2016) is an English version of the revised article by Krzysztof Czaplewski “Kryterium całkowe jako narzędzie matematyczne wspomagające proces optymalizacji wystawienia stacji systemu nawigacyjnego”4 , published in ZN AMW No. 3/2000. The authors would like to apologize for having forgotten to include this article in the reference section, which mistake was noticed after the article had been published. The authors' intention was not to conceal the previous publication, but to return to the previous studies on navigation processes optimization devised by one of the authors. The authors considered it desirable to get back to the previous results, as the problems of automatization of optimization processes are still valid in navigation and require further work. Furthermore, the subject of the article lies in the area of studies currently performed by the authors. In the context of increasingly frequent information on spoofing and jamming of satellite system signals, ground-based radio navigation systems begin to grow in significance again. For example, the contemporary mutation of the Loran system called eLoran seems to be at the time the best option supporting the operation of GNSS. The erection of new eLoran stations or other systems supporting the operation of GNSS has to be preceded by reliable optimization studies among others, and this is the reason why the authors are interested in this area of studies. We would like to apologize to anyone who felt offended by the situation.