• Title/Summary/Keyword: isolines of rotation

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A GIS-based Analysis on Geometric Distortions in Historical Maps: A Preliminary Case Study of Daedongyeojido ('The Great Map of Korea') (고지도의 왜곡 양상에 대한 GIS-기반 연구: 대동여지도를 사례로 한 시론적 분석)

  • Lee, Sang-Il;Cho, Daeheon
    • Journal of the Korean Geographical Society
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    • v.49 no.3
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    • pp.438-455
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    • 2014
  • This study aims at providing a set of viable answers regarding the projection and cartographic scale of Daedongyeojido through a GIS-based planimetric accuracy analysis. Both global and local analyses were undertaken in the use of an analytical tool, MapAnalyst. The main results from the global analysis are threefold. First, the overall cartographic scale turned out to be between 1:158,000 and 1:162,000. Second, the rotation angles were between $2^{\circ}$ and $3^{\circ}$, and the equidistant cylindrical projection reported the smallest value. Third, in terms of position accuracy, the conformal cylindrical projection showed a best fit to the map. A local analysis was undertaken for the conformal cylindrical and equidistant azimuthal projections and its main results are threefold. First, the largest distortions in terms of the displacement vectors and distortion grid were found in the northern borderlands. Second, from the isoline maps of scales, it was acknowledged that local scales between 1:170,000 and 1:175,000 were found around the middle part of the Korean peninsula centered on Seoul. As away from the region to the north-south direction, increasingly larger scales were distributed, while the smallest ones were found in the western and eastern edges of the peninsula. Third, from the isoline maps of rotation, it was known that areas west of a northernmost city (Junggangjin) were substantially rotated to the west, while ones east of it to the east. For a more sophisticated analysis, some need to be done to have a larger set of control points, a better way of postulating the map projection, and a more advanced set of techniques for a local analysis.

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