ノート

アウトライン

An Interactive Method for Joining Spatial Data Units Takashi Sato Department of Urban Engineering, University of Tokyo, Japan Yukio Sadahiro Atsuyuki Okabe Center for Spatial Information Science, University of Tokyo, Japan 2001.3.2

Study Objectives

Study Objectives Existing methods Manual method →Time consuming Automatic method →Uncontrollable / Excessive deformation

Three Steps of Joining Maps

1.Extraction of Boundary Nodes

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"Selection of Boundary Nodes" Selection of Boundary Nodes

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2. Detection of Matching Nodes Iterative search of the nearest node pairs

3.Transformation of the Central Map Global transformation The similarity transformation that minimizes the square sum of the node-to-node distances of the matching nodes

3. Transformation of the Central Map Local transformations Isomorphic transformation using triangular tessellation

"Transformation function at X" Transformation function at X v (X) = sa・{t・v (B)+(1-t)・v (A)}

"Isomorphism of the Transformation" Isomorphism of the Transformation

3. Transformation of the Central Map Estimation of the parameter a The similar transformation is desirable.

Empirical Examples

Empirical Examples

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Conclusions Advantages of our method to existing methods It works almost automatically. We can control transformation interactively in each step. The transformation function is explicitly determined. It does not using attribute information of line objects including identification numbers. It uses both global and local transformations to join maps, keeping the topology of original lines.

Discussion Extensions of This Study Non-rectangular maps →Historical maps →Dynamic update      of spatial data Polygon data

Discussion Spatial data of different accuracy Spatial data made by different mapmakers for details see http://www.csis.u-tokyo.ac.jp/dp/34.pdf