AERIAL PHOTOGRAMMETRY USING A BALLOON PLATFORM

為有效了解地表資訊，可視研究目的而利用各種遙測方法獲取地面影像，但不論目前常用之飛機、或是以衛星為載具之空中攝影測量等相關研究，在影像獲取方面，常面臨成本費用、機動性、比例尺需求、後續影像處理等問題。因此，本研究選定一小流域面積之河川作為實驗區，並設計以氣球為載具之數值航空攝影方式，裝載CCD攝影機以及數位攝影機，透過CCD攝影機，即時無線傳輸地面影像至監視螢幕，調整氣球至預定之位置後，遙控啟動數位攝影機之快門裝置。 研究設計之攝影方式曾實際應用於偵測河道之變遷，由成果影像中檢核點之精度結果，以及套疊正射糾正並鑲嵌後之河道影像與地形圖之成果，證明氣球載具之數值航空攝影方式，確能有效應用於大比例尺製圖之研究。 Using a flexible and efficient way to obtain aerial images has been the primary purpose of this study. The balloon platform was used to take aerial images. A video camera and a digital camera were fixed together in a durable plastic box, and hung on the balloon. The video camera was used to monitor the ground view, and its image could be telemetered remotely and displayed on a LCD monitor arranged on the ground. Once monitoring the area of interest shown on the LCD, the shutter button of the digital camera was then pushed remotely and the interested image was taken. The resultant images were ortho-rectified for analysis and comparison. The accuracy of aerial images was examined by check points. The results showed that the images achieved sub-pixel accuracy and were well-matched with the 1/1000 digital topographic maps. This expressed that it was really a useful and efficient method of taking large-scale images for a small research area. At last, post-classification comparison method was introduced to detect change of the ortho-rectified images which were taken in three different periods. The classification maps and the from-to change class information clearly indicated the change of river way among various periods