利用交點法與內插法計算山坡地坡度之比較研究

Abstract

坡度是描述地形的重要因子，也是山坡地開發時關切的重點，亦有許多不同的坡度演算方法已被提出。本研究針對「等高線與方格交點法」與「內插網格法」進行比較，前者於現有法規與工程實務中廣為使用，後者則是以數值地形圖檔經過內插步驟後利用三次加權方法計算而得。 結果顯示內插網格法擁有較高的穩定性，受人為操作差異而變化的程度較小；然而平均坡度卻大為降低，可開發面積大幅增加，這可能使山坡地開發問題更為嚴重。解決辦法為縮小網格單元，將原本25公尺的規定網目細分為三分之一大小，並採用除碎方法以及提高坡度門檻，如此將仍保有高穩定性，並使可開發面積縮小，以降低山坡地開發之壓力。

Slope gradient is an important factor when we describe a terrain or develop in a slopeland. While many methods calculating slope gradient have been developed, in this study two methods are exercised: the intersection method is by counting the crosses of contours and orthogonal squares and is currently recognized as an official method in Taiwan; the other is by calculating in third weighted method from an interpolated grid. This study concludes that the interpolated grid method is more stable than the intersection method, but gets flatter slope gradients which cause more areas will be developed and endanger the environmental sustainability. A solution is to minify the cell size to one third of the original size, with removing fragment units and setting a more strict slope threshold .Thus, the stability can be kept and the developable slope area can be reduced.