Graduation of Sjors Allersma

Digitalization of Vessel Traffic Management in Port Areas

• Professor of graduation: Prof. dr. ir. M. van Koningsveld

• Supervisors of graduation: Ir. E. Bolt (Rijkswaterstaat), Dr. ir. W. Daamen (TU Delft), H. van Dorsser MSc (Port of Rotterdam)

Introduction
While navigating through ports, vessels get assisted by the Vessel Traffic Service (VTS). Information is communicated using very high frequency (VHF) radios on the corresponding VHF-channels of the VTS-sectors. In busy sectors in the port, these VHF-channels are very crowded, which results in unclear situations and high workloads for the VTSOs. The Rotterdam Port Authority is currently investigating measures to reduce VHF-traffic.

To define effective measures, it is required to understand by which factors the VHF-communications are triggered. In this thesis, a quantitative method has been developed to investigate whether VHF-communications are caused by certain properties of a fairway system. In order to verify this, the substantive, spatial and temporal characteristics of both the VHF-communications and a considered fairway property have to be identified first. Subsequently, the spatial and temporal characteristics of the VHF-communications are linked to spatial and temporal characteristics of a property of the fairway system, to analyse whether the occurrence of a particular form of VHF-communication is related to the occurrence of that particular property of the waterway system. The method can be applied to investigate the individual influence of several fairway properties, but in this research the focus is on analysing to what extent the fairway property “blocked view” leads to the development of VHF-communications. To investigate whether VHF-communications are related to the occurrence of visual obstructions, a model has been developed to estimate the visibility for varying locations and vessel parameters.

Objective
The objective of this research is to investigate to what extent a “blocked visibility” for vessels is likely to trigger VHF-communications in port areas. 

VHF-Analysis
To identify the substantive, spatial and temporal characteristics of the VHF-communications, the spoken VHF-data has to be digitized first. The digitization is achieved by converting spoken VHF-audio bands to text, then dividing this text into different conversations and finally classifying each phrase according to place, time and content. A subsequent analysis of the obtained data is executed into communication types, involved participants and observing vessel locations.

Visibility-Analysis
To map the visibility of vessels, a model has been set up to determine the visibility around a chosen observation point. The visibility is dependent on the elevations in the surrounding environment of the observer point, the elevations of the observation- and target point and the detection range. The model is based on the viewshedanalysis, which determines the visibility of the surrounding environment by means of the line-of-sight-principle. The output of the model consists of a viewshed in which the visible and invisible areas, as seen from the observer location, are indicated. The visibility of a location is expressed in the form of a “blockage factor” (BF), which defines the percentage of invisible waterways in the vicinity of the observation point. See figure 1.

Visibility in Traffic Images
Finally, the results of both analyses are combined to verify whether the occurrence of a particular form of VHFcommunication is related to blocked view. This is done for the VHF-communications regarding traffic images. For each communicated traffic image it has been verified whether the addressed targets have been visible for the observing vessel in question and whether traffic images have been communicated to vessels located on locations with higher BF’s. See figure 2 for an overview of the observing vessel locations and corresponding BF’s.

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