Automatic Identification System (AIS) is a data exchange system which was introduced to improve shipping safety and the possibility of exchanging data, at a country and international level, about ships heading to or from ports, as well as exchanging data relating to passengers and dangerous or environment-polluting cargo carried by ships. The main purpose of introducing AIS was to offer a wider spectrum of available, continuous and reliable navigational data. Apart from being useful for traffic control in a marine area, AIS data can be a very important source of information used in collision avoidance process. However, some reservations are voiced with regard to the unconditional reliance on the data transferred through this channel. The information integrity problem had been raised already at the stage of system implementation and some fragmentary outcomes were published in the past. However, it can be assumed that the results from the system introduction period may not represent reality. Thus, it seems reasonable to base the assessment on theoretical analysis, through the development of multi-criteria model describing the AIS information integrity. The research was performed on data recorded in the period between 04.04.2006 r. and 08.01.2012 r. (selected 55 weeks– 385 days) in the laboratory of Institute of Navigation and Hydrography. Only full 24-hour recordings of AIS signals were selected for the analysis. Fifty five measurement sessions were used to determine the limit probability for availability and integrity exponential of information system, expected value of system lifetime, expected value of system failure time, failure rate, renewal rate. Utilizing homogenous Markov Chains, prediction of the state of availability and integrity of selected AIS information components was carried out. The proposed research approach in many cases gave differentiated results. The research outcomes presented in the paper lead to the conclusion that AIS could deliver useful supplementary information in the process of collision avoidance.
At a glance
- Availability analysis uses 55 weeks of AIS recordings from the Hel base station
- Integrity research uses 371 days of recorded AIS information
- Research tool development uses 6,320 ship records from the MarSSIES system
- Develops an AIS decoder and a tool for availability and integrity coefficients
- 95 sources in the bibliography
Table of Contents
INTRODUCTION
1. DEFINITION OF RESEARCH PROBLEM
1.1. General remarks
1.2. Objectives and thesis dissertation
2. SUMMARY OF THE AIS FUNCTIONING
2.1. Introduction
2.2. Idea of AIS introduction
2.3. Information transmitted by AIS used in the dissertation
2.4. AIS network structure of the Gulf of Gdansk
2.5. AIS malfunctions
3. REVIEW OF AVAILABILITY AND INTEGRITY METHODS AND TOOLS FOR AIS INFORMATION RESEARCH
3.1. Methods and tools for research of AIS information integrity
3.1.1. Application of statistic methods to research AIS service information
3.1.2. Statistical analysis of AIS information in accordance with N.Bailey theory
3.1.3. End-user satisfaction model
3.2. Research methods and tools of AIS information availability
3.2.1. Research method of AIS information availability by A.Hori
3.2.2. Research method (LIC) of AIS availability and coverage area in accordance with Lapinski & Isenor
3.2.3. Research method (HPC) of AIS availability and coverage area in accordance with Hammond & Peters
4. RESEARCH METHODOLOGY FOR ESTABLISHING THE PROBLEM THROUGH AVAILABLE TOOLS AND MODELS
4.1. Preliminary presentation of research models
4.1.1. General remarks
4.1.2. Option 1 – Method for research of AIS information integrity with the use of Fault Tree Analysis (FTA)
4.1.3. Option 2 – Method for research of AIS information availability and integrity with the use of Markov Processes
4.1.3.1. Definitions
4.1.3.2. Stationary distribution
4.2. Remedy research by available models and tools
4.2.1. General remarks
4.2.2. Developing data - "post-processing"
4.2.3. Decoding AIS information
4.2.4. Assumption for availability research of AIS information
4.2.5. Availability structure of AIS information – determination of the object study
4.2.6. Assumption for integrity research of AIS information
4.2.7. Evaluation completeness criteria of AIS information
4.2.8. Completeness structure of AIS information – determination of the object study
4.2.9. Evaluation integrity criteria of AIS information
4.2.9.1. Evaluation integrity criteria of AIS message No. 1
4.2.9.2. Evaluation integrity criteria of AIS message No. 5
4.2.10. Preliminary assumptions of integrity research for AIS information
5. RESEARCH SOLUTION
5.1. Characteristics of input data
5.2. Research outcomes of AIS binary data availability
5.3. Research method of AIS information availability
5.4. Research outcomes of information completeness concerning true heading
5.5. Research method of AIS information completeness concerning true heading
5.6. Research outcomes of information completeness concerning rate of turn
5.7. Research method of AIS information completeness concerning rate of turn
SUMMARY, CONCLUSION, DIRECTION OF FURTHER RESEARCH
Objectives and Topics
The dissertation asks whether recorded AIS messages can support forecasts of navigational information availability and integrity. It develops a mathematical model based on homogeneous Markov processes and investigates recorded traffic in the Gulf of Gdansk.
- AIS operation, messages and sources of error
- Existing approaches to information quality and coverage
- Decoding and post-processing recorded AIS messages
- Availability modelling using base-station reports
- Completeness of true heading and rate-of-turn information
- Markov-chain prediction and transition probabilities
Excerpt from the Book
4.1.1. General remarks
AIS provides information of various types - numerical and textual, fixed and variable. The correctness of information can be assessed only by comparison with real information, hence the task becomes complex. So far, publications on the matter include descriptions of AIS integrity research based on statistical analysis of static information errors. Other research method involves the use of multiple regression model. The main assumption in this case was to evaluate the user satisfaction of AIS information on the basis of the conducted surveys.
It is worth noting that the navigation system is expected to maintain efficiency under defined conditions and in the defined time interval duration of the navigation task. This is not always understood in terms of the navigation characteristics in the context of information abstracted from the device. In terms of navigation, we are not satisfied only with the device functioning –it has to provide true information.
The content of Chapter 2 presents the essence of AIS functioning. In addition, it presents the problem of reducing the information integrity of the system. This indicates the need of developing AIS information integrity model. The limited information integrity of the system is associated with the lack of true or complete information derived from the system receiver. Pilot study and statistical analysis of the research outcomes contained in [Felski A, Jaskólski K, 2010]provide additional arguments to support this conclusion.
It is possible to apply reliability theory for evaluation of the information integrity. For this purpose, the theory of fuzzy sets, neural networks, expert and probabilistic methods are used. Other research methods of information integrity use statistical analysis of the data obtained from AIS. In addition, the results of surveys carried out in a group of system users are also used. Section 4.1.2 and 4.1.3 present two variants of problem solution.
Chapter Summaries
INTRODUCTION: Introduces AIS information quality and the hypothesis that availability and integrity can be predicted. It outlines the research stages and methods.
1. DEFINITION OF RESEARCH PROBLEM: Establishes the navigation-safety context, research objectives and main and auxiliary theses.
2. SUMMARY OF THE AIS FUNCTIONING: Explains AIS messages, the Gulf of Gdansk network and operational limitations affecting information quality.
3. REVIEW OF AVAILABILITY AND INTEGRITY METHODS AND TOOLS FOR AIS INFORMATION RESEARCH: Reviews statistical, user-satisfaction and coverage-estimation approaches, including LIC and HPC.
4. RESEARCH METHODOLOGY FOR ESTABLISHING THE PROBLEM THROUGH AVAILABLE TOOLS AND MODELS: Compares fault-tree analysis with Markov processes and develops decoding and assessment criteria for recorded messages.
5. RESEARCH SOLUTION: Applies the proposed models to base-station availability and the completeness of true heading and rate-of-turn information.
SUMMARY, CONCLUSION, DIRECTION OF FURTHER RESEARCH: Synthesizes the research outcomes, methodological contributions and possible extensions.
Keywords
Automatic Identification System, AIS, information availability, information integrity, information completeness, Markov chains, stochastic processes, maritime safety, Gulf of Gdansk, base stations, true heading, rate of turn, post-processing
Frequently Asked Questions
What is the dissertation about?
It examines the availability, completeness and integrity of navigational information transmitted through AIS.
What are its central themes?
Its themes include AIS operation, data quality, transmission availability, message decoding and probabilistic modelling.
What is the main research objective?
The objective is to develop a mathematical model for assessing and forecasting AIS information availability and integrity.
What research method is used?
The author post-processes recorded AIS messages and applies homogeneous Markov chains to model transitions between information states.
What does the main analysis cover?
It examines base-station transmission availability and the completeness of selected dynamic information, particularly true heading and rate of turn.
Which keywords characterize the work?
Key terms include AIS, availability, integrity, completeness, Markov chains, maritime safety and post-processing.
Why is the Hel base station important to the study?
Its base-station reports, received in Gdynia, provide the recorded signals used to investigate transmission-channel availability.
How are the criteria for lines and ships different?
The line criterion relates to received message records, while the ship criterion relates to the vessels transmitting the information.
Which AIS messages are examined?
The study uses position reports numbered 1, 2 and 3, base-station report 4, and static and voyage-related message 5.
- Quote paper
- Krzysztof Jaskólski (Author), 2014, Availability and integrity model of Automatic Identification System (AIS) Information, Munich, GRIN Verlag, https://www.grin.com/document/278255
