Browsing by Author "Silveira, P."
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- AIS Based Shipping Routes Using the Dijkstra AlgorithmPublication . Silveira, P.; Teixeira, A.P.; Guedes Soares, C.This paper proposes an approach for identifying and characterizing shipping routes using information contained in Automatic Identification System messages broadcasted by ships and recorded by the coastal Vessel Traffic Service centre. The approach consists of using historical Automatic Identification System data to build a graph, where nodes are cells of a grid covering the geographical area being studied and the weights of directional edges are inversely related to ship movements between cells. Based on this graph, the Dijkstra algorithm is used to identify a potential safe route, assumed to be the most used route by ships between two locations. A second graph is created simultaneously, with the same nodes and edges, but with edge weights equal to the average speed of transitions between cells, thus allowing the determination of the average speed profile for any possible path within the graph. The proposed approach is applied to two scenarios: an approach to the port of Lisbon and the entry through the fairway to a RO-RO terminal in the port of Setubal in Portugal.
- 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.