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PublicationAnalyzing temporal usage patterns of street segments based on GPS data - a case study in SwitzerlandMobility has become a key component of our social and economic activities. Depending on our activities, the usage of the road network varies, showing, for example, an increased traffic load in early morning when people go to work. Such usage patterns are of interest not only for traffic management but also for private companies offering location-based services. In this paper we analyze the temporal usage of street segments based on a large GPS data set in Switzerland. We first conduct a clustering analysis which detects groups of segments with similar temporal usage patterns. Afterwards we analyze the patterns with respect to their temporal and spatial characteristics. Our analysis shows that GPS data is qualified for an analysis of temporal usage patterns, identifying shopping and leisure activities.
PublicationRobustness analyses for repeated mobility surveys in outdoor advertisingA growing number of companies use mobility data in their day-to-day business. However, as the data grows older, new data has to be collected in order to keep applications up-to-date. Consequently, it is of great importance to know the impact that a different mobility sample may cause. This aspect of analysis has been largely neglected in mobility data mining research so far. In this paper we therefore analyze the robustness of performance measures with respect to a changed GPS sample in outdoor advertisement. The evaluation of outdoor advertising campaigns is a challenging application because it requires the evaluation of mobility data on a very fine spatial level. Thus, the application has a higher dependency on routes of individual test persons than classical mobility surveys. In our rob ustness analysis we apply bootstrapping and subsampling in order to measure the effect of a) a repeated mobility survey and b) a mobility survey of smaller size. We conduct our experiments on a real-world data set from Swiss outdoor advertising. Our results show that the effect is comparably small for a typical campaign and may be mitigated further by increasing the campaign size.
PublicationModeling micro-movement variability in mobility studiesDuring the past years the interest in the exploitation of mobility information has increased significantly. Along with these interests, new demands on mobility data sets have been posed. One particular demand is the evaluation of movement data on a high level of spatial detail. The high dimensionality of geographic space, however, makes this requirement hard to fulfill. Even large mobility studies cannot guarantee to comprise all movement variation on a high level of detail. In this paper we present an approach to increase the variability of movement data on microscopic scale in order to achieve a better representation of population movement. Our approach consists of two steps. First, we perform a spatial aggregation of trajectory data in order to counteract sparseness and to preserve movement on macroscopic scale. Second, we disaggregate the data in geographic space based on traffic distribution knowledge using repeated simulation. Our approach is applied in a real-world business application for the Ger-man outdoor advertising industry to measure the performance of poster sites.
PublicationRäumlich differenzierte Reichweiten für die AußenwerbungDer Raum ist seit jeher ein wichtiger Bestandteil der Außenwerbung. Aus plausiblen Gründen werden Plakatstandorte so gewählt, dass sie häufig von Menschen gesehen werden. Während jedoch der Raum bei der Wahl von Plakatstandorten schon immer ein entscheidendes Kriterium gewesen ist, spielt er bei der Leistungsbewertung und damit bei der Preisbildung von Plakatstandorten erst seit den vergangenen Jahren eine wichtige Rolle. Neue, GPS-basierte Messmethoden erlauben die räumlich differenzierte Ausweisung von Leistungswerten für beliebig zusammengestellte Kampagnen und Zielgruppen. In diesem Artikel stellen wir am Beispiel der Schweiz die alte und neue Methodik zur Erfassung von Reichweitenleistungen gegenüber. Anhand von Beispielen mit real existierenden Messdaten der schweizer Außenwerbung zeigen wir, wie die Außenwerbung durch räumlich differenzierende Verfahren in der Leistungsbewertung von Kampagnen profitiert.
PublicationHandling missing values in GPS surveys using survival analysisGPS technology has made it possible to evaluate the performance of outdoor advertising campaigns in an objective manner. Given the GPS trajectories of a sample of test persons over several days, their passages with arbitrary poster campaigns can be calculated. However, inference is complicated by the early dropout of persons. Other than in most demonstrations of spatial data mining algorithms where the structure of the data sample is usually disregarded, poster performance measures such as reach and gross impressions evolve continuously over time and require non-intermittent observations. In this paper, we investigate the applicability of survival analysis to compensate for missing measurement days. We formalize the task of modeling the visit potential of geographic locations based on trajectory data as our variable of interest results from dispersed events in space-time. We perform experiments on the cities of Zurich and Bern simulating different dropout mechanisms and dropout rates and show the adequacy of the applied method. Our modeling technique is at present part of a business solution for the Swiss outdoor advertising branch and serves as pricing basis for the majority of Swiss poster locations.