應用數位航測技術於三義火炎山地形變遷之研究

A Study on the Geomorphological Change in Hoyenshan Nature Reserve

陳永寬(Yeong-Kuan Chen) ； 葉堃生(Kuen-Sheng Yeh) ； 詹進發(Jihn-Fa Jan)

《航測及遙測學刊》 5卷1期 (2000/03) Pp. 17-31

https://doi.org/10.6574/JPRS.2000.5(1).1

摘要

本研究以三義火炎山自然保留區為試驗區，利用四期航空照片為材料，（1）以全球衛星定位系統測量地面控制點；（2）以數位航空測量技術蒐集地形特徵資料點；（3）以影像自動匹配技術自動化生產各期規整網格數值地形模型。然後，分析比對此等數值地形模型，計算土壤沖蝕量與地形變化量，探討歷年地形地貌變遷。應用影像自動匹配技術生產DTM資料，直接受到照片品質與重疊率之影響。為提高匹配成功率與正確度，如於匹配失敗區及地形特殊區，以人工作業加測地形斷線，取代原自動匹配高程，構造新TIN，再進行內插產生規整高程點，則較理想。森林覆蓋區，自動匹配所獲得者為數值覆蓋面模型。用以萃取水系分佈與集水區邊界以探討邊坡後退的變化情形則可；如用於土方變化分析時，則須事先排除林木覆蓋區域，以免土方計算受到林木生長的影響。本研究結果顯示，影響火炎山地形變化之因素眾多，頻度、強度、地點不定，難以計算出單一變化模式。若僅欲了解地形地貌變遷之表象，則使用多期航空照片，以數位航測技術配合適度人工斷線測量，自動化生產數值地形模型分析之，應不失為安全、省時、省事之方法。

關鍵字

地形地貌變遷 ； 數位航測 ； 數值地形模型 ； 影像自動匹配 ； 土方分析

並列摘要

In this research, the Hoyenshan Nature Reserve at Sanyi was selected as the study site. This research utilized aerial photos obtained in four different years to investigate the soil erosion in the study area. Specific procedures of the research include: (1) to obtain coordinates of ground control points applying GPS surveying; (2) to collect data of topographic features using digital photo-grammetry; (3) to establish DTMs applying automatic matching techniques. Finally, by analyzing those DTMs, we quantify the soil erosion and establish a model for evaluating the geomorphological change within the study area. When applying automatic matching technique in collecting DTM points, the quality and percentage of overlap of the aerial photos usually affect the results. To obtain better results, manual digitization of break lines is required for those areas that have poor results in previous runs, then the interpolation is performed to generate regular DTM points. Automatic matching is based on the gray values of digital images, therefore, digital surface model (DSM) is obtained through the process. The results indicate that DSM can be used to derive drainage system and watersheds, the geomorphological change can then be e valuated by comparing the drainage systems and watersheds of different years. To estimate the volume of soil loss, however, the areas covered by forest should be excluded so that the computed volume is not affected by the tree growth. The geomorphological change of the study area is affected by many factors. More-over, the frequency, intensity, and locations are varying. Therefore, it is very difficult to model the geomorphological change. However, based on the volume and rate of soil loss, it is estimated that the unique geomorphologic features of the study area should still remain for a long period of time.

並列關鍵字

geomorphological change ； digital photogrammetry ； digital terrain model ； automatic image matching ； soil volume analysis