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DOI: 10.4230/DagSemProc.08471.2
Propagating and measuring anchor uncertainty in space-time prisms on road networks

Authors: Bart Kuijpers, Harvey J. Miller, Tijs Neutens, and Walied Othman

Published in: Dagstuhl Seminar Proceedings, Volume 8471, Geographic Privacy-Aware Knowledge Discovery and Delivery (2009)

Abstract
Space-time prisms capture all possible spatio-temporal locations of a moving object between sample points given speed limit constraints on its movement. These sample points are usually considered to be perfect measurements. In this paper we restrict ourselves to a road network and extend the notion of sample points to sample regions, which are bounded, sometimes disconnected, subsets of space-time wherein each point is a possible location, with its respective probability, where a moving object could have originated from or arrived in. This model allows us to model measurement errors, multiple possible simultaneous locations and even flexibility of a moving object. We develop an algorithm that computes the envelope of all space-time prisms that have an anchor in these sample regions and we developed an algorithm that computes for any spatio-temporal point the probability with which a space-time prism, with anchors in these sample regions, contains that point. We implemented these algorithms in Mathematica to visualise all these newly-introduced concepts.
Cite as

Bart Kuijpers, Harvey J. Miller, Tijs Neutens, and Walied Othman. Propagating and measuring anchor uncertainty in space-time prisms on road networks. In Geographic Privacy-Aware Knowledge Discovery and Delivery. Dagstuhl Seminar Proceedings, Volume 8471, pp. 1-35, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2009)

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@InProceedings{kuijpers_et_al:DagSemProc.08471.2,
  author =	{Kuijpers, Bart and Miller, Harvey J. and Neutens, Tijs and Othman, Walied},
  title =	{{Propagating and measuring anchor uncertainty in space-time prisms on road networks}},
  booktitle =	{Geographic Privacy-Aware Knowledge Discovery and Delivery},
  pages =	{1--35},
  series =	{Dagstuhl Seminar Proceedings (DagSemProc)},
  ISSN =	{1862-4405},
  year =	{2009},
  volume =	{8471},
  editor =	{Bart Kuijpers and Dino Pedreschi and Yucel Saygin and Stefano Spaccapietra},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/DagSemProc.08471.2},
  URN =		{urn:nbn:de:0030-drops-20072},
  doi =		{10.4230/DagSemProc.08471.2},
  annote =	{Keywords: Space-time prisms, beads, prisms, uncertainty, flexibility, time-geography}
}
Document
DOI: 10.4230/DagSemProc.07212.4
An analytic solution to the alibi query in the bead model for moving object data

Authors: Bart Kuijpers and Walied Othman

Published in: Dagstuhl Seminar Proceedings, Volume 7212, Constraint Databases, Geometric Elimination and Geographic Information Systems (2007)

Abstract
Moving objects produce trajectories, which are stored in databases by means of finite samples of time-stamped locations. When also speed limitations in these sample points are known, beads can be used to model the uncertainty about the object's location in between sample points. In this setting, a query of particular interest, that has been studied in the literature of geographic information systems (GIS), is the alibi query. This boolean query asks whether two moving objects can have physically met. This adds up to deciding whether the necklaces of beads of these objects intersect. This problem can be reduced to deciding whether two beads intersect. Since, existing software to solve this problem fails to answer this question within a reasonable time, we propose an analytical solution to the alibi query, which can be used to answer the alibi query in constant time, a matter of milliseconds or less, for two single beads and in time proportional to the product of their lengths for necklaces of beads.
Cite as

Bart Kuijpers and Walied Othman. An analytic solution to the alibi query in the bead model for moving object data. In Constraint Databases, Geometric Elimination and Geographic Information Systems. Dagstuhl Seminar Proceedings, Volume 7212, pp. 1-22, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2007)

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@InProceedings{kuijpers_et_al:DagSemProc.07212.4,
  author =	{Kuijpers, Bart and Othman, Walied},
  title =	{{An analytic solution to the alibi query in the bead model for moving object data}},
  booktitle =	{Constraint Databases, Geometric Elimination and Geographic Information Systems},
  pages =	{1--22},
  series =	{Dagstuhl Seminar Proceedings (DagSemProc)},
  ISSN =	{1862-4405},
  year =	{2007},
  volume =	{7212},
  editor =	{Bernd Bank and Max J. Egenhofer and Bart Kuijpers},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/DagSemProc.07212.4},
  URN =		{urn:nbn:de:0030-drops-12864},
  doi =		{10.4230/DagSemProc.07212.4},
  annote =	{Keywords: Beads, uncertainty, alibi, query, solution, quantifier elimination, constraint database}
}
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