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The paper investigates the representation of moving-point objects in databases

Capturing the Uncertainty of Moving-Object Representations

SSD, (1999): 111-132

被引用642|浏览16
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摘要

Spatiotemporal applications, such as fleet management and air traffic control, involving continuously moving objects are increasingly at the focus of research efforts. The representation of the continuously changing positions of the objects is fundamentally important in these applications. This paper reports on on-going research in the re...更多

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简介
  • A relatively new research area, spatiotemporal databases concerns the management of objects with spatiotemporal extents, and real-world objects with continuously changing spatial extents are attracting substantial attention.
  • Applications managing past data often conduct analyses of movements over time, answering queries such as, “What were the movements of the Vikings in the North Sea between year 1000 and year 1200?” Applications dealing with present and future data capture the current spatial extents of objects in the database and typically make predictions about the future extents of the objects.
重点内容
  • A relatively new research area, spatiotemporal databases concerns the management of objects with spatiotemporal extents, and real-world objects with continuously changing spatial extents are attracting substantial attention
  • “What is the position of flight SAS 286?” and “Where will flight SAS 286 be in 20 minutes?” a specific type of application concerns real-world objects that move continuously and disregards the spatial extents of the objects, representing instead their positions as points
  • The paper investigates the representation of moving-point objects in databases
  • A set of queries derived from requirements to an application managing moving-point objects is presented
  • As we shall see this method can only be applied if the probability specified in the query is less than 50%
  • The Global Positioning System is the technology used for obtaining samples of the positions of these objects
结果
  • As the authors shall see this method can only be applied if the probability specified in the query is less than 50%.
  • Shrinking the query window by the size of the negative expansion measure would eliminate this position from the set of candidate solutions.
  • This problem is solved by using the original query window with no expansion for probabilities higher than 50%.
  • Would exclude qualifying positions, e.g., position P would be discarded in the filter step, 30% or more of its actual positional probability is concentrated within the query window
结论
  • The paper investigates the representation of moving-point objects in databases.
  • A set of queries derived from requirements to an application managing moving-point objects is presented.
  • The Global Positioning System is the technology used for obtaining samples of the positions of these objects.
  • The positions of objects are sampled at selected points in time, and the positions in-between these points in time are obtained using interpolation, capturing the complete movement.
  • The representation of movements is inherently imprecise, and the paper considers two types of errors, the measurement error and the sampling error.
  • It is further shown that the measurement error can be ignored in the application context considered
总结
  • Introduction:

    A relatively new research area, spatiotemporal databases concerns the management of objects with spatiotemporal extents, and real-world objects with continuously changing spatial extents are attracting substantial attention.
  • Applications managing past data often conduct analyses of movements over time, answering queries such as, “What were the movements of the Vikings in the North Sea between year 1000 and year 1200?” Applications dealing with present and future data capture the current spatial extents of objects in the database and typically make predictions about the future extents of the objects.
  • Results:

    As the authors shall see this method can only be applied if the probability specified in the query is less than 50%.
  • Shrinking the query window by the size of the negative expansion measure would eliminate this position from the set of candidate solutions.
  • This problem is solved by using the original query window with no expansion for probabilities higher than 50%.
  • Would exclude qualifying positions, e.g., position P would be discarded in the filter step, 30% or more of its actual positional probability is concentrated within the query window
  • Conclusion:

    The paper investigates the representation of moving-point objects in databases.
  • A set of queries derived from requirements to an application managing moving-point objects is presented.
  • The Global Positioning System is the technology used for obtaining samples of the positions of these objects.
  • The positions of objects are sampled at selected points in time, and the positions in-between these points in time are obtained using interpolation, capturing the complete movement.
  • The representation of movements is inherently imprecise, and the paper considers two types of errors, the measurement error and the sampling error.
  • It is further shown that the measurement error can be ignored in the application context considered
表格
  • Table1: Parameters of the probability function, P2, describing the sampling error vm maximum speed of the moving object tx time for which the error distribution is computed t1 time of the first measured position t2 time of the second measured position s distance between the two positions, i.e., the length of the line segment A lens area, i.e., the area of the intersection of the two circles
  • Table2: Relational schema for capturing moving-point objects, their trajectories, and associated error information
Download tables as Excel
基金
  • This research was supported in part by the CHOROCHRONOS project, funded by the European Commission, contract no
  • FMRX-CT96-0056, by the Danish Technical Research Council through grant 9700780, and by the Nykredit Corporation. The Mathematica software package (Wolfram 15) was used to compute the probability functions shown in Figs. 5(a) and (b)
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