Christian Vetter

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C hierarchies are a simple approach for fast routing in road networks. Our algorithm calculates exact shortest paths and handles road networks of whole continents. During a preprocessing step, we exploit the inherent hierarchical structure of road networks by adding shortcut edges. A subsequent modified bidirectional Dijkstra algorithm can then find a(More)
Time-dependent road networks are represented as weighted graphs, where the weight of an edge depends on the time one passes through that edge. This way, we can model periodic congestions during rush hour and similar effects. In this work we deal with the special case where edge weights are time-dependent travel times. Namely, we consider two problems in(More)
Contraction hierarchies are a simple hierarchical routing technique that has proved extremely efficient for static road networks. We explain how to generalize them to networks with time-dependent edge weights. This is the first hierarchical speedup technique for timedependent routing that allows bidirectional query algorithms. For large realistic networks(More)
Routing services on the web and on hand-held devices have become ubiquitous in the past couple of years. Websites like Bing or Google Maps allow users to find routes between arbitrary locations comfortably in no time. Likewise onboard navigation units belong to the off-the-shelf equipment of virtually any new car. The amount of volunteered spatial data of(More)
Time-Dependent Contraction Hierarchies is a routing technique that solves the shortest path problem in graphs with time-dependent edge weights, that have to satisfy the FIFO property. Although it shows great speedups over Dijkstra’s Algorithm the preprocessing is slow. We present a parallelized version of the preprocessing taking advantage of the multiple(More)
We provide an implementation of an exact route planning algorithm on a mobile device that answers distance queries in a road network of a whole continent instantaneously, i.e., with a delay of 20–200ms, which is virtually not observable for a human user. We exploit spatial and hierarchical locality properties to design a significantly compressed(More)
Server based route planning in road networks is now powerful enough to find quickest paths in a matter of milliseconds, even if detailed information on time-dependent travel times is taken into account. However this requires huge amounts of memory on each query server and hours of preprocessing even for a medium sized country like Germany. This is a problem(More)
BACKGROUND Health-related quality of life in adults with congenital cardiac disease appears to be impaired, but the determinants of this alteration remain largely unknown. The aim of our study was to examine the impact of arrhythmias on quality of life in patients late after the atrial redirection operation for transposition, or after complete correction of(More)
BACKGROUND Improved endothelial function may contribute to the beneficial effects of cholesterol lowering therapy in patients with coronary artery disease (CAD), but results of the effect of statin therapy on endothelial function are disparate in these patients. Exercise training has been reported to improve endothelial function of patients at risk of or(More)