The SV1 service - NAMAS(Navigation Monitoring & Assistance Service) collects ship’s position data in all South Korean waters, and predicts the next positions, calculates the CPAs between ships within a certain distance, evaluates basic collision risk and each vulnerability, then integrates to the navigational collision risk. This paper describes the functions and background chosen in the navigation risk solving system; Data characteristics, framework of navigation risk solving system, and data structures and methods for efficient computation for CPA calculations and detecting accident risk situations.