臺灣歷史航照影像糾正對位

航照像片是地表現象的忠實記錄，歷史航照影像直接地記錄過去某個時間點的地表現象，包括當時的土地利用、自然資源、道路及聚落等空間分布，能夠呈現過去人文社會、經濟活動與自然環境的變遷。臺灣主要的歷史航照包括美軍(1943~1952年)、空軍(1954~1976年)以及農林航空測量所(1976年至今)所拍攝累積的照片。要利用這些歷史航照影像，以萃取時空地理資訊，必須將這些影像糾正對位到共同的坐標系統上。本文以台江內海區域為例，將不同時期的空照影像糾正對位到現行的國家坐標系統(TWD97)。農林航空測量所的影像屬製圖應用的標準航測影像，可應用空中三角測量的方法進行幾何糾正並產製正射影像。然而美軍及空軍的航拍目的主要為軍事偵察，所使用的相機無明確的內方位資訊，影像的重疊也不符合航測的標準，無法以制式的空中三角測量法進行糾正對位。本研究嘗試以聯合解算方式，求得同時期所有重疊影像的仿射轉換參數，獲得糾正對位的資訊。此方法雖然不如空中三角平差嚴謹，但是可以在無相機內方位資訊的情形下，獲得整體的對位成果。實驗結果顯示，應用此方法於美軍空照影像，其定位內部精度可達6.5m，相對於以空三解算農林航空測量所影像的定位精度(2m)，雖然較低，但此對位精度相信已經符合於時空地理資訊分析的需求，可推廣歷史航照的應用。

關鍵字

歷史航照影像；對位；空中三角測量；仿射轉換

並列摘要

Aerial images are faithful records of landscape at that time. Historical aerial images directly witness landscape phenomena at that time of the covered region, including land-use, natural source, roads and residential area, etc. The study of historical aerial images has proven an effective way to reveal some historical phenomena related to cultural, economic, and natural changes, which are linked to the spatial information in the past. Abundant historical aerial images have been acquired in Taiwan for a variety of missions. The earliest aerial images were taken by U.S. military during and after World War II (from 1943 to 1952). Later than that many images were acquired routinely by Taiwan Air Force (1954 to 1976), Aerial Survey Office (since 1976). For the purpose of retrieving spatial information from the historical images, image registration and rectification corresponding to the ground coordinates should be done in advance. In this study, we take Tai-jiang Inner Sea as an example to register and rectify temporal aerial images into nowadays national coordinate system (TWD97). Images acquired by Aerial Survey Office are standard aerial images which can be registered through a computation process of bundle adjustment. However, the main purposes of images taken by U.S. military and Taiwan Air Force were mainly applied for military reconnaissance. These images are lack of camera parameters and the overlapped of them are not standard. So they do not fit the process of bundle adjustment. In this study, we attempt to obtain the information of registration and rectification by solving affine transformation parameters from all overlapped images at the same period. Although this method are not as strict as aerial triangulation, it can work without camera parameters. The experimental results showed that the accuracy of images taken by U.S. military can up to 6.5 m by applying affine transformation. The accuracy was poor than images taken by Aerial Survey Office using aerial triangulation (2m). But we believe this can meet the analysis of temporal geographic information and promote the application of historical aerial images.

並列關鍵字

historical aerial images ； registration ； triangulation ； affine transformation

國際替代計量

臺灣歷史航照影像糾正對位

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