A Study on the Simplification Algorithms for Map Linear Features

• Main Authors: Guo-Shou Deng, 鄧國壽
• Other Authors: Cheng-Hsiung Tseng
• Format: Others
• Language: zh-TW
• Published: 2003
• Online Access: http://ndltd.ncl.edu.tw/handle/70775933414526433075

碩士 === 國防大學中正理工學院 === 軍事工程研究所 === 91 === For conforming to the objective of mapping, in the process of modifying the geographic data to be represented in a smaller map space, cartographic generalization is to reduce the data and retain the important feature, conserve the best geometric and descriptive characteristics, while keep the map clearly. There is software for digital cartographic generalization having been presented to the public, but in the generalization automation, the function of system is still under development to be researched and overcome for completeness; yet in the interactive approach, operators must confront how to select appropriate algorithms to perform generalization. Therefore it is an urgently important topic for study how to assist the cartographers in selecting appropriate algorithms to perform generalization in quantities and swiftly for digital mapping by assessing algorithms, so that they can utilize the databases of large-scale digital maps to produce various maps. This research investigated the linear features of maps aiming at roads, rivers and coastlines, and the four simplification algorithms─Douglas, Li-Openshaw, Bendsimplify and Shape algorithm─were used to generalize these linear features from 1:25,000 scale to 1:50,000 scale, then took the generalizations into the quantitative and qualitative assessments of the four simplification algorithms. Quantitative assessments based on the ratios of the change in number of coordinates and in line length, and qualitative assessments based on the survey of opinions of cartographers. Finally showed that the Douglas algorithm can conserve the better geometric characteristics than the three others.