關鍵詞：偏移偵測法、格陵蘭冰層、合成孔徑雷達
6. 結論與建議
根據上述各測試之經驗，包含比較總計四種光 學與雷達影像，並透過多光譜、主成分分析、罩窗 大小、偏極與資料型式及成像幾何差異後，可歸納 結論如下：
(1)偏移偵測法對於光學影像本身之正射品質有極 高要求，而目前高解析度之免費影像中又以 Landsat-8 有最好之品質。
(2)空間解析度較波段反射度差異有更大之影響，
故以 Landsat-8 之全色態波段有最佳成果。
(3)在空間解析度不足之狀況下，執行主成分分析 相關處理並無法有效改善成果細節與品質。
(4)搜尋罩窗大小必須大於主從影像時間間隔內之 地表位移，然超過此一門檻後再增大罩窗並無顯 著效果，並將耗費大量執行時間。
(5)合成孔徑雷達影像之偏移偵測成果，以經 Log 處理後之分貝與 HH 偏極影像有最完整而正確 之成果。
(6)時間相仿之升降軌雷達影像成果極為相似，故 不受到成像幾何影響。
由以上結論可之，若欲透過衛載影像執行偏移 偵測法以監測快速變動且地貌不穩定之冰河位移 情況，以光學影像而言應選用最高解析度之感測器 或波段，其次方考慮各波段之地貌對比差異；而雷 達影像則應選擇 HH 之分貝影像。處理方面，則應 測試後選擇超過變動量大小之罩窗大小，方可正確 進行監測。
致謝
承蒙中華民國行政院科技部專題研究計畫(計 畫編號：MOST 106-2420-H-004-015-MY3)與韓國 Ministry of Land, Infrastructure and Transport 研究 計畫 Greenland mapping project 經費支持，以及 JAXA(ALOS RA-6 dataship No. 3238)與 ASIAQ Greenland Survey 提供影像與地面測量資料，本研 究方得以順利完成，謹此申謝。
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1 Master, Department of Land Economics, National Chengchi University Received Date: Apr. 02, 2018
2 Associate Professor,Department of Land Economics, National Chengchi University Revised Date: Apr. 30, 2018
3 Senior Research Fellow, Dept. of Geoinformatics, University of Seoul, Korea Accepted Date: May. 04, 2018
* Corresponding Author, E-mail: [email protected]