Planimetric accuracy of old maps: Tan-Hsin Archives maps
Date Issued
2011
Date
2011
Author(s)
Huang, Ya-Ni
Abstract
In cartography, the map accuracy studies have developed their particular approaches and methods.Since the 20th century, numerous cartography researchers have explored the map accuracy from various aspects, including history, culture, nature, technology. However, most of them studied the planimetric accuracy. This study used MapAnalyst as the main tool to investigate the planimetric accuracy of Tan-Hsin Archives maps and go further on visualizing the errors of maps by other GIS software. Tan-Hsin Archives are the Qing Dynasty’s official documents, generated by a local government in Taiwan, including valuable written documents and a great number of old maps. The time span of Tan-Hsin Archives lasted from 1776 to 1895. Tan-Hsin Archives contain 1164 cases, covering the areas of Tansui Prefecture, Taipei Government, and Hsin-chu County in the Qing Dynasty.
Owing to the development of digital mapping and analysis technology, tools for analyzing map accuracy are becoming much powerful and versatile. MapAnalyst is an open software program aiming to analyze maps accuracy. Developed by Bernhard Jenny and Adrian Weber in 2005, this software can analyze and represent planimetric accuracy of maps. Most of all, it is equipped with visualization capability for measuring maps’ distortion, rotation, displacement, and deformation. The indicators for visualizing map errors by MapAnalyst include distortion grids, displacement vectors and circles, and standard inaccuracy circles. This study analyze two Tan-Hsin maps: No.17339_60_13 and No.22510_16. There are three questions to be answered in this study. First, from the aspect of social construction of maps, how is Tan-Hsin maps’ planimetric accuracy and why do the two maps have different accuracy? Second, after the visualization process, what are the differences between the two maps? Third, what are the factors of the visualization process and how do they affect the process? The results showed that No.17339_60_13 and No.22510_16 maps’ directions respectively rotated 39 and 17 degrees counterclockwise. The scales of Taiwan Bauto and the two maps were 1:2.5 and 1:3.4. In terms of the two maps, the differences of scales and mapping purposes may result in the difference of planimetric accuracy. Moreover, the results showed that the mesh width had main influence on how obvious the errors of maps and that the mixed pixels affected the contrast.
In short, the main purpose of this study is to establish a process of visualizing map accuracy from the traditional 2D analysis to the 3D exploration. This study used simple tools and methods to realize this process and provided an integrative approach for the future studies.
Subjects
Tan-Hsin Archives
map accuracy
old map
Type
thesis
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