舊有鋼筋混凝土結構(Reinforced concrete structures, RC)其承載力評估的最重要參數(Parameters)即為鋼筋數量及鋼筋品質(強度)，然而針對已完工的鋼筋混凝土結構，目前尚困難取得鋼筋數量之相關資訊。因此在承載力(或耐震)評估或結構補強中(Reinforcement)，舊有鋼筋數量的確認一直是工程師困擾的問題，例如，同一棟建築使用不同數量的鋼筋(或箍筋)時，其塑性鉸(Plastic hinge)的位置及後續補強數量也將有所差異，這也是耐震評估時常被提出討論的焦點。 非破壞檢測(nondestructive testing, NDT)的技巧已廣泛應用於土木工程的品質檢測、驗收。然而目前為止，雖然有相當多的檢測方法，但要快速且準確的檢測出非均質混凝土(non-homogeneous concrete)內部鋼筋尺寸及位置，仍有一些困難。本研究提出圖像定位方法應用一般放射線對物質(γ)具有穿透能力的特性，利用影像處理軟體讀取及處理顯示元件之影像，用以消除影響影像品質的因素，並配合著影像的放大或縮小倍率及投影幾何原理，以外加控制點方式直接在照片影像上推算混凝土內鋼筋尺寸或孔洞位置，因此本法可使平面影像具有斷層攝影效果。案例顯示，本法能推算預力梁中套管埋設深度，以及內部瑕疵(鋼線斷裂或灰泥漿孔洞)。 ;One important parameter in assessing the carrying capacity of reinforced concrete (RC) is the steel quantity and quality (Strength). However, for a completed RC structure, difficulty exists in obtaining steel intensity data. The assessment for carrying capacity (or seismic) or structural reinforcements, existing steel quantity can become an issue for engineers. For example when different steel (or different stirrupt) quantity exist in the same structure its plastic hinge position and reinforcement numbers may vary. This is also a debatable topic concerning the seismic assessments. Non-destructive testing (NDT) is widely used for quality inspection, acceptance check in civil engineering. Although there have numbers of detection methods, However, it is difficult to accurately identify voids or steel location in highly non-homogeneous concrete. In this research, application of the radiation on materials (γ) has the ability to penetrate characteristics. a radiographic positioning method is proposed to eliminate factors against image quality. An image positioning software is used to exhibit and modify the target image such that image distortions can be prevented, and the percentage of zooming-in or zooming -out can be calculated by the software. The principle of geometrical projection and external control points are directly applied to identify reinforced steel size or honeycomb position from the images. The proposed method can make plane image achieve topographical effect. Case shows, this method can calculate the casing depth in pre-stressed girders and calculate the inside defects (wire breakage or gray holes).