A method for locating landmarks on a cephalogram is disclosed. In the method, at first a plurality of tracing papers of sample cephalograms are provided, wherein each of the tracing papers has landmark coordinates. Thereafter, a first feature capturing step is performed on each of the tracing papers to capture tracing paper features of each of the tracing papers. Then, a second feature capturing step is performed to capture cephalogram features of a target cephalogram. Thereafter, a feature comparing step is performed to select a minimum error tracing paper from the tracing papers in accordance with the cephalogram features and the tracing paper features. Then, a landmarks adjusting step is performed to adjust coordinates of the landmarks of the minimum error tracing paper in accordance with the features of the minimum error tracing paper and the target cephalogram to obtain coordinates of the land marks of the target cephalogram.本發明係揭露一種測顱片界標定位方法。在此測顱片界標定位方法中，首先提供測顱片之描軌圖樣板，其中每一樣板描軌圖具有描軌圖界標點座標。接著，對每一描軌圖進行第一特徵擷取步驟，以擷取每一描軌圖之描軌圖特徵。然後，進行第二特徵擷取步驟，以擷取目標測顱片之測顱片特徵。接著，進行特徵比較步驟，以根據測顱片特徵和每一描軌圖之描軌圖特徵，來從描軌圖中選取最小誤差描軌圖。然後，進行界標點調整步驟，以根據測顱片特徵和最小誤差描軌圖之描軌圖特徵，來調整最小誤差描軌圖之描軌圖界標點座標，以獲得測顱片之測顱片界標點座標。
