關鍵字：UAV、三維建模、密匹配、SGM、PMVS
4. 實驗分析
4.2 數值地形模型重建分析
以 MUAV 進行垂直拍攝地表，通常應用在數
值地表模型或正射影像圖，上述兩者都需有點雲資 訊才能獲得，因此本研究中驗證這過程中的點雲資 料，提供後續資料處理的正確性。
選擇 23 個航標點作為檢核用，分別位於柏油 道路共 10 點、草地共 6 點、河谷中央共 4 點、河 谷底共 3 點，等不同地表特徵之航標點作為檢核，
由完成密匹配後點雲，經由 CloudCompare 軟體，
以人工識別方式數化出航標點雲，透過數化出點雲 計算平均值作為航標中心坐標。
將求得航標點雲中心坐標與實際量測點坐標 點，計算不同地貌分佈航標的平面、高程、整體之 均方根誤差(RMSE)作為精度，計算結果如表 2。
表 2 不同地貌處航標點精度
方法 PMVS SGM
精度(公尺) 平面 高程 整體 平面 高程 整體 柏油路 0.055 0.065 0.085 0.049 0.054 0.073
草地 0.062 0.068 0.092 0.076 0.079 0.110 河谷中央 0.078 -0.075 0.108 0.073 0.068 0.100 河谷底 0.083 -0.081 0.116 0.081 0.073 0.109 表中柏油道路在兩種密匹配中精度一致，因柏 油道路的影像 GSD 的大小較為平均，所以柏油道 路精度差異不大；草地區利用 SGM 有產製的點雲 有分層的現象，使數化過程中比較困難，相對其精 度顯得較差些；河谷中央距離地面約為 15 公尺、
河谷底距離地面為 30 公尺，河谷越深相對航高變 化越大，點雲的精度越低，僅在高程部分 SGM 略 高一些 PMVS。
另外以重建完成後的點雲分佈進行檢視，可發 現在於使用 PMVS 在於紋理相同的區域，容易發 生點雲空洞的問題，如圖 16 框選部分都是屋頂為 鋼鐵或鐵皮材質的部分， SGM 對於這些區域都有 點雲的資訊，如圖 17 所示。在處理效能上 SGM 為 69 分鐘完成，另外 PMVS 則以 135 分鐘完成製作，
雖 SGM 的製作時間快，但 SGM 比 PMVS 所產製 的點雲數量多，相對需要儲存的容量比較大。
200
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1 Ph.D. Student, Department of Civil Engineering, Received Date: Aug. 01, 2016 National Kaohsiung University of Applied Sciences Revised Date: Oct. 06, 2016
2 Associate Professor, Department of Civil Engineering, Accepted Date: Dec. 23, 2016 National Kaohsiung University of Applied Sciences
* Corresponding Author, Tel: 886-7-3814526 ext.5245, E-mail: [email protected]