The article introduces the request of the International Maritime Organization (IMO) for accuracy of vessel position and the maximum interval between two consecutive ship positions. The author focuses on assessing the extent to which IMO’s requirements are met when planning a voyage, based on practical experience from himself and a number of other outstanding captains. At the same time, analyse theoretical and practical basis when making decisions about the limited distance to the danger point and the time interval between two determinations of consecutive ship locations to ensure maritime safety. The article builds the process of calculating and manipulating maritime routes to estimate safety through dangerous areas with full theoretical basis and practical seafaring experience.