Though the number of marine accidents tends to decrease, nearly 2,000 ships have been involved in marine accidents every year for the last 10 years in Japan. More than 70% of ships involved in the accidents are boats such as pleasure boats and fishing boats. In this paper, we focused on collision avoidance support for boats by using collision alerts. There are two ways to support collision avoidance by using collision alerts; one is a guard-zone alert using position information and the other is a collision alert based on Closest Point of Approach (CPA) analysis using information of position, course and speed. Evaluation of communication time in information processing is necessary to provide timely support regardless of the aforementioned ways. Automatic Identification System (AIS) and radar Target Tracking (TT) are used for collision avoidance support. However, they are not suitable for boats because of their costs and sizes. Meanwhile, smartphones become popular in late years. When smartphones provide sufficient accuracy of information for collision avoidance support, they can be practical and useful onboard devices to support boats. In this paper, we clarified communication time, accuracy of position, course and speed obtained by smartphones that affect collision alerts.
This paper argues that an adaptive extended Kalman filter (EKF) improves the performance of global navigation satellite system (GNSS) position, velocity, and time (PVT) and their integrity information by single point positioning in dense urban environments without sensor aiding or coupling. One of the most important, as well as difficult problems of single point positioning in urban environments, is the negative impact of non-line-of-sight (NLOS) signals, which cause significant and unexpected measurement errors that degrade the PVT performance of conventional positioning methods. To reduce this impact, an adaptive EKF was implemented for single point positioning. Six laps of test drives were conducted to prove that the adaptive EKF drastically reduces the position and velocity errors and removes outliers when compared to a conventional EKF. Moreover, the adaptive covariance matrix contributed to the integrity information. The horizontal and vertical protection levels (HPL/VPL) of both the position and velocity computed by the covariance matrix of the state vector were degraded for the conventional EKF; however, when they were measured using the adaptive EKF, the degradation was restrained. Thus, the adaptive EKF could be proposed as a simple and effective technique to reduce the negative impact of NLOS and to improve the GNSS performance in heavy-NLOS environments for any type of GNSS receiver.
This paper focuses on an analysis of a questionnaire survey regarding ULCV masthead lights as a means for determining LOA for ocean-going deck officers and coast guard officers. The contents of the questionnaire survey investigate ① The difference between the estimated ULCV LOA by naked eye observation of masthead lights and the actual ULCV’s LOA ② The effects of illuminating side passage lights as an aid to estimating ULCV LOA ③ The amendment of regulations relating to the ULCV’s legal lights (masthead lights, side lights, stern light, etc.).
Analysis of the results suggest that ① Respondents were not able to estimate the ULCV LOA by naked eye observation of the masthead lights ② Respondents were able to estimate the actual ULCV LOA by observing the illuminating side passage lights case, and ③ Respondents gave negative responses concerning the necessity of amending the regulations.
After a background review of this issue, this paper will analyze the data from the questionnaire results, and finally discuss conclusions and offer some suggestions for measures to correct any problems, as well as directions for future research.