遙測影像幾何校正是資料整合應用前的必要工作。傳統正射改正程序僅處理傾斜移位以及地形起伏所產生的高差移位。對於高空間解析度影像，因為影像內涵豐富，含有更細微的地表資訊，地表物高程在像空間會產生高差移位及遮蔽現象。此造成都市區影像中，高樓和立體交會之道路系統於正射影像中仍有嚴重的幾何變形。 真實正射校正考量地表物的高度，改正和補償地表物造成的高差位移和遮蔽，使真實正射影像可得目標物的正確位置。本研究範疇所處理的目標物針對人工建物 (房屋、道路)，故研究中整合房屋、道路和地形模型產生真實正射影像。 研究中所使用的資料包括：三維房屋模型、三維道路模型和數值地形模型以描述物空間地表不同區塊的高低起伏，校正影像則使用多視角的高解析空照影像。其中研究主要程序有：(1)視線分析 (2)遮蔽偵測 (3)遮蔽區補償 (4)陰影區增揚。研究中使用UltraCam-D數位空照影像進行校正，研究的測試區分別位於桃園、中央大學和台北。 Geometric correction of remote sensing imagery is indispensable for the purpose of data integration and applications. Conventional ortho- rectification only considers the correction of tilt displacements and terrain relief displacements. Since high-resolution imagery captures more detailed information, the abrupt changes of object elevation result in the relief displacements and occlusions in image space. In urban areas, high-rise buildings and multi-layer road systems of orthoimages cause serious image deformation. True-orthorectification procedures take account of ground objects for the correction of relief displacements and compensation of the hidden areas. Accordingly, the true orthoimages provide the exact position of land objects. This research focuses on the man-made constructions, including buildings and roads. Thus, the generation of true orthoimages is done by integration of building, road, and terrain models. The test data comprise three dimensional building models, road models and digital terrain models, and multi-view aerial images are employed for the compensation of hidden areas. The proposed scheme includes：(1) visibility analysis, (2) hidden detection, (3)hidden compensation, and (4)shadow enhancement. Three test sites includies Tauyuan, National Central University, and Taipei. UltraCam-D imagery is used to validate this research.
