Noyon, Valérie (2007) A relative and spatio-temporal model of geographic trajectories. PhD thesis Informatique, IRENav, Ecole navale, ENSAM 2007ENAM0023 p.218.

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Abstract

The worldwide increase of transportation traffic implies a progressive obstruction of many air, terrestrial and

maritime routes. This also augments the number of security risks and enlarges the complexity of monitoring and

regulation tasks. Over the past few years, maritime transportation and traffic have been improved by the emergence of new technological solution oriented towards real-time geo-localisation such as the GPS (Global Positioning System) and VHF systems(Very High Frequency). With continuous and real-time availability of location data on

ship displacements (e.g. position, speed), trajectories are usually represented using either an absolute (cartographic

view) or relative representation (e.g. radar view). These systems, used independently or through a dual mode, while

they are successful in providing a global or partially local view of the geographical environment, does not provide a

complete and appropriate representation of the way a mobile object and its observer act in and perceive the

maritime environment.

The research presented in this thesis introduces a new conceptual model oriented to the representation of geographical trajectories in space and time. We consider the point of view where a displacement process is perceived by an egocentric representation and visualisation of space and time, and where the modelling primitives are the ones usually retained by a Geographic Information System. Our study shows that the relative speed and distance are appropriate concepts that support an egocentric-based modelling of an object and observer behaving in a maritime environment. The relative position is based on the distance between two given objects, but also makes a difference between the value of their topological relationships. Similarly, the relativised speed also makes a

difference between faster and slower moving objects with respect to a referent moving object. This representation

is designed on top of a two-dimensional space, this facilitating characterisation of the underlying spatio-temporal

processes using natural language terms. Continuous transitions are also identified. Overall this modelling approach offers novel perspectives for the visualisation and analysis of trajectories in space and time. The approach is

supported by a prototype applied to a maritime context and several experiments made with panels of users.

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