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.
Table of Contents
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
Objectives and Research Focus
The primary objective of this dissertation is to develop a mathematical model of AIS information integrity and availability based on homogeneous Markov processes to address the current lack of forecasting methods for AIS information errors and sensor-related inaccuracies.
- Analysis of AIS system imperfections and existing investigative approaches to information integrity.
- Development of a specialized decoding methodology and tools for assessing AIS information unfitness.
- Application of stochastic homogeneous and semi-Markov chains to determine transition probabilities between system states.
- Empirical analysis of AIS information availability and integrity using data collected in the Gulf of Gdansk.
- Verification of statistical hypotheses regarding system state predictability and information quality metrics.
Excerpts from the Book
1. DEFINITION OF RESEARCH PROBLEM
According to International Regulations for Preventing Collisions at Sea, Rule V “Look-out” [Rymarz W., 1998] „Every vessel shall at times maintain a proper look-out by sight and hearing as well as by all available means appropriate in the prevailing circumstances and conditions so as to make a full appraisal of the situation and of the risk of collision”. Effective look-out should ensure early detection of objects. Another task is to assess ship motion parameters and foresee situation development. One of the effective undertakings is radar look-out in any conditions of visibility, especially, when the vessel navigates in area of intensive traffic at night. It is commonly known that Radar and ARPA have some efficacy limitations [8]. Detection of small objects is limited by sea clutters and unfavourable weather conditions (rain, snowstorm) as well as by radio-transmitters operating on similar frequencies. Characteristic phenomenon is the appearance of death-zone (minimum range of detection), radar shadow effect (due to reflections from funnel, mast and other constructions on the vessel) and wave reflection.
As far as ARPA devices are concerned, automatic tracking of objects can be lost during torrential ship manoeuvring or when passing ships within close distance.
In practice, the position information is characterized by a an error not less than about 30 meters, while at higher radar ranges error position may be greater than 100m.
Summary of Chapters
1. DEFINITION OF RESEARCH PROBLEM: This chapter defines the research problem, outlines the dissertation objectives, and provides general remarks regarding the necessity of AIS reliability assessment in the context of collision avoidance.
2. SUMMARY OF THE AIS FUNCTIONING: This chapter summarizes the fundamental operation of the AIS, the idea behind its introduction, the structure of the AIS network in the Gulf of Gdansk, and common system malfunctions.
3. REVIEW OF AVAILABILITY AND INTEGRITY METHODS AND TOOLS FOR AIS INFORMATION RESEARCH: This chapter reviews the current state of knowledge and existing methods for assessing AIS information integrity and availability, including statistical methods and specific research models.
4. RESEARCH METHODOLOGY FOR ESTABLISHING THE PROBLEM THROUGH AVAILABLE TOOLS AND MODELS: This chapter presents the research methodology, including Fault Tree Analysis (FTA) and the application of Markov Processes as a core analytical framework for evaluating system information.
5. RESEARCH SOLUTION: This chapter details the research outcomes, including characteristics of input data and the application of the developed methodology to analyze the availability and completeness of AIS information.
Keywords
Automatic Identification System, AIS, Information Integrity, Information Availability, Markov Processes, Fault Tree Analysis, Navigation Safety, Data Transmission, Gulf of Gdansk, Stochastic Models, Data Completeness, Marine Navigation, System Reliability, Post-processing, Vessel Traffic Service
Frequently Asked Questions
What is the core focus of this dissertation?
The work focuses on assessing the availability, completeness, and integrity of data provided by the Automatic Identification System (AIS) to ensure it can be reliably used for navigation and collision avoidance.
What are the primary themes of the study?
Key themes include the modeling of AIS information quality, the analysis of transmission channel availability, the identification of human and sensor-based errors, and the prediction of system state transitions.
What is the primary goal of the research?
The primary goal is the development of a mathematical model using homogeneous Markov processes to forecast the availability and integrity of AIS information.
Which scientific methods are applied in the study?
The study primarily employs stochastic methods, specifically homogeneous Markov chains, alongside Fault Tree Analysis (FTA) and multivariate statistical analysis of recorded AIS data.
What is covered in the main body of the work?
The main body covers the review of existing research methods, the definition of an analytical framework for AIS information, the development of post-processing tools for data decoding, and the presentation of empirical results from the Gulf of Gdansk.
Which keywords best characterize the research?
Key terms include AIS, Information Integrity, Markov Processes, Navigation Safety, Data Completeness, and Stochastic Modeling.
How is the availability of the AIS transmission channel determined?
Availability is determined by analyzing recorded AIS message traffic, specifically evaluating the reception of Base Station reports (Message No. 4) and applying Markov Chain models to classify the system as either in a working state or a failure state.
What role does the "post-processing" method play?
The post-processing method is used to conduct statistical analysis on recorded historical AIS data to identify trends, errors, and system states that were not detectable during real-time operation.
How are human errors integrated into the analysis?
Human errors, particularly regarding static and voyage-related data entry, are accounted for as critical factors in the degradation of AIS information integrity and are categorized using the developed analytical framework.
- Citation du texte
- Krzysztof Jaskólski (Auteur), 2014, Availability and integrity model of Automatic Identification System (AIS) Information, Munich, GRIN Verlag, https://www.grin.com/document/278255
