地圖簡化是一種由较大比例尺地圖轉换到较小比例尺的一项過程，而該作業過程之良窳，則控制了资訊傅播管道之暢通舆否。在地圖资料組合中，以線符號所占比例最高，而在向量式數值地圖中比例更高，因此地圖線符號簡化即爲数值地圖舆地理资訊系就中一项重要之工作。數值地圖線條簡化之方法極多，其中以Douglas-Peucker法较符合地圖認知舆製作方式。然因地圖簡化目的，主要爲保留且反映當地地理環境之整體概觀，故該法中容許值之訂定，則爲極重要项目。本文即以臺灣地區海岸線爲例，探討不同地理區舆容許值間之關連，以了解簡化過程中其舆海岸線長度及面積變化特性，並據此以訂定簡化初期各地理區最適切之容許值。此外，該法亦可當作地圖簡化初期清除雜訊之方法，在文中亦以實例加以說明。

Cartographic generalization is a process that transforming geo-information from large-scale through small-scale, so, it controls the communication efficiency of map information. Linear features are dominant in conventional maps, and own even higher percentage in the vectorized maps; therefore, line generalization is important in the map-making and geographic information systems. Line generalization algorithms are many kinds, Douglas-Peucker's algorithm (1973) is the pertinent, and the determination of its tolerance value is the most important one, as to approach the goal of keeping the true figue of geographic environment. The aim of this study is to find the relationships that lie between tolerance value and geomorphological characterisitics of different coastlines of Taiwan area. Thus the tolerance value of different regions can be defined. Besides, it can also be used as a noise-wiping method in the preparing period of generalization, this will be demonstrated here.