Browsing by Author "Teixeira, A. P."
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- A method to extract the Quaternion Ship Domain parameters from AIS dataPublication . Silveira, P.; Teixeira, A. P.; Soares, C. GuedesThe ship domain concept is of great interest for ship traffic modelling, risk assessment and intelligent collision avoidance. The paper proposes and applies a method to define AIS data-based empirical polygonal ship domains, based on traffic density matrices that are derived around each reference ship from an AIS dataset. A modified Quaternion Ship Domain allowing for different shapes for each quadrant is proposed, which results in a better fitting to the empirical domain. The parameters of Quaternion Ship Domains that best fit the empirical polygonal domains are determined for cargo ships and tankers of different lengths. Violations of the Quaternion Ship Domain are then used as an indicator of collision risk that is graphically represented in the study area, providing important information to support maritime traffic monitoring and control tasks.
- A multicriteria outranking approach for ship collision risk assessmentPublication . Silveira, P.; Figueira, J. R.; Teixeira, A. P.; Soares, C. G.The paper presents a judgmental expert-based process to assess the ship collision risk using the ELECTRE Tri-nC multiple criteria outranking method. The approach first establishes a set of criteria deemed important by navigation experts, all of them experienced nautical officers, to assess the collision risk between two ships in open waters. A deck of cards-based method is then used to determine the weights of each criterion, according to the experts’ preferences. Finally, risk categories chosen by the experts are characterised in terms of multiple reference scenarios, also provided by the experts, and the ELECTRE Tri-nC method is used to assign validation scenarios to the risk categories. The results are compared with the experts’ assessments of the collision risk for the same scenarios and also with the individual assessments made by three experts that have not participated in the development of the decision model.
- Preliminary analysis of the fishing activity in PortugalPublication . Lotovskyi, E.; Teixeira, A. P.; Silveira, P.; Torrão, E.Despite more than 3000 national fishing vessels land daily in Portuguese waters, the fishing activity and the spatial-temporal patterns of this fleet are still poorly characterised and documented. This poses some difficulties to a rational approach for maritime operation planning, control, monitoring, safety and security of the fishing activity. This paper conducts a preliminary analysis of the fishing activity in Portugal. First, the most used fishing gears and a portrait of the Portuguese licensed fishing fleet are presented. Current monitoring systems used to support control and surveillance tasks are described and their limitations discussed. The trajectories of fishing vessels in a selected area are then analysed using Automatic Identi-fication System data. The vessels’ trajectories are grouped by practiced fishing gear and a preliminary characterization of the phases and of the motion patterns per group is conducted
- Probabilistic modelling of evasive manoeuvring actions to avoid collisionsPublication . Silveira, P.A.M.; Teixeira, A. P.; Soares, C. Guedes