Matthias Delafontaine

Implementing a qualitative calculus to analyse moving point objects

Research highlights? Generic conceptual model to analyse MPOs through a Qualitative Trajectory Calculus (QTC). ? Implementation prototype for a QTC-based information system (QTCAnalyst). ? Case study 1: using QTCAnalyst to analyse a traffic situation in QTC-Basic. ? Case study 2: using QTCAnalyst to analyse a squash game in QTC- Double-Cross. Due to recent technological advances in position-aware devices, data about moving objects is becoming ubiquitous. Yet, it is a major challenge for spatial information systems to offer tools for the analysis of motion data, thereby evolving from static to dynamic frameworks. This paper aims to contribute to this area by introducing an implementation prototype for an information system based on the Qualitative Trajectory Calculus, a spatiotemporal calculus to represent and reason about moving point objects.

The impact of opening hours on the equity of individual space-time accessibility.

Abstract While many studies have concentrated on the effects of the spatial distribution of services on individual accessibility, only little is known about the ways in which equity of individual accessibility is affected by the temporal organisation of service delivery. This paper seeks to deepen our understanding about the relationship between accessibility, equity and the opening hours of public service facilities on the basis of space–time accessibility measures. Three approaches based on different equity principles are presented to schedule the opening hours of public service facilities: a utilitarian, an egalitarian and a distributive approach. A case study of public libraries in Ghent (Belgium) demonstrates the relevance of these approaches for amending the opening hours of public services to control the equity of accessibility levels across individuals.

A GIS toolkit for measuring and mapping space–time accessibility from a place-based perspective

This article introduces a novel geographical information system toolkit for measuring and mapping the accessibility of individuals to services. The toolkit contributes to earlier implementations by combining aspects of both place-based and person-based accessibility measures. To this end, place-based accessibility measures are derived from a person-based framework by considering space–time prisms that are centred at service facilities rather than individual anchor points. The implementation is also innovative by explicitly accounting for the opening hours of service delivery in its accessibility measurement. In addition, the toolkit is aimed to be user-friendly and to generate insightful and comprehensible results for non-technically oriented users, which is illustrated in a brief case study about library accessibility in Ghent (Belgium).

Spatial variation in the potential for social interaction: a case study in Flanders (Belgium)

Empirical evidence is mounting that good urban design fosters the formation of social fabric. Existing evidence is however limited in at least two respects. First, empirical studies have focused largely on social interactions taking place within the residential neighborhood, while leaving social encounters near the workplace unconsidered. Second, while various studies have examined the impact of the built environment on realized social behavior, there is as yet no empirical research on the potential for having social contact. A deeper understanding of the geography of social interaction potential is nonetheless important, for it is individuals’ social opportunities rather than their preferences and actual choices that are most directly amenable to policy intervention. This paper seeks to address both issues in an empirical case study in Flanders and Brussels (Belgium). An exploratory spatial analysis is conducted to uncover spatial trends in the potential for social interaction in order to better understand the role of urban spatial structure in the production of social interaction potential.

Modelling potential movement in constrained travel environments using rough space-time prisms

The widespread adoption of location-aware technologies (LATs) has afforded analysts new opportunities for efficiently collecting trajectory data of moving individuals. These technologies enable measuring trajectories as a finite sample set of time-stamped locations. The uncertainty related to both finite sampling and measurement errors makes it often difficult to reconstruct and represent a trajectory followed by an individual in space–time. Time geography offers an interesting framework to deal with the potential path of an individual in between two sample locations. Although this potential path may be easily delineated for travels along networks, this will be less straightforward for more nonnetwork-constrained environments. Current models, however, have mostly concentrated on network environments on the one hand and do not account for the spatiotemporal uncertainties of input data on the other hand. This article simultaneously addresses both issues by developing a novel methodology to capture potential movement between uncertain space–time points in obstacle-constrained travel environments.

Interactive analysis of time intervals in a two-dimensional space

Time intervals are conventionally represented as linear segments in a one-dimensional space. An alternative representation of time intervals is the triangular model (TM), which represents time intervals as points in a two-dimensional space. In this paper, the use of TM in visualising and analysing time intervals is investigated. Not only does this model offer a compact visualisation of the distribution of intervals, it also supports an innovative temporal query mechanism that relies on geometries in the two-dimensional space. This query mechanism has the potential to simplify queries that are difficult to specify using traditional linear temporal query devices. Moreover, a software prototype that implements TM in a geographical information system (GIS) is introduced. This prototype has been applied in a real scenario to analyse time intervals that were detected by a Bluetooth tracking system. This application shows that TM has the potential to support a traditional GIS to analyse interval-based geographical data.

Assessment of sliver polygons in geographical vector data

As positional error is a major issue in the assessment of spatial data quality, its propagation has been studied widely in map overlaying. However, few studies deal with a manifest consequence of positional error in map overlaying, namely sliver polygons. Sliver polygons are generally treated as awkward by-products that need to be removed quickly. Nevertheless, as they represent spurious areas, their nature and properties carry useful information, for example, for land use/cover assessment. Therefore, next to sliver removal, there is a need for intelligent detection and eventually further analysis of sliver polygons. This article proposes a general, semi-automated method for the assessment of slivers in vector polygon layers. A case study in Flanders (Belgium) illustrates a possible application in area estimation evaluation of land use allocation classes.