Abstract
Historical aerial photographs directly provide good evidences of past times. The Research Center for Humanities and Social Sciences (RCHSS) of Taiwan Academia Sinica has collected and scanned numerous historical maps and aerial images of Taiwan and China. Some maps or images have been geo-referenced manually, but most of historical aerial images have not been registered since there are no GPS or IMU data for orientation assisting in the past. In our research, we developed an automatic process of matching historical aerial images by SIFT (Scale Invariant Feature Transform) for handling the great quantity of images by computer vision. SIFT is one of the most popular method of image feature extracting and matching. This algorithm extracts extreme values in scale space into invariant image features, which are robust to changing in rotation scale, noise, and illumination. We also use RANSAC (Random sample consensus) to remove outliers, and obtain good conjugated points between photographs. Finally, we manually add control points for registration through least square adjustment based on collinear equation. In the future, we can use image feature points of more photographs to build control image database. Every new image will be treated as query image. If feature points of query image match the features in database, it means that the query image probably is overlapped with control images.With the updating of database, more and more query image can be matched and aligned automatically. Other research about multi-time period environmental changes can be investigated with those geo-referenced temporal spatial data.
Highlights
1.1 Value of Historical Aerial PhotographWith development of camera and aerial technology, aerial photograph and remote sensing images play a vital role within the geographical environmental study
Many kinds of image data have increased since past to so analysis of temporal environmental changes become available with multi-period aerial photographs
We developed an efficient way for matching historical aerial photographs and generating tie points automatically, and we only need to manually add some control points from recent satellite image for the final network adjustment
Summary
With development of camera and aerial technology, aerial photograph and remote sensing images play a vital role within the geographical environmental study. Many kinds of image data have increased since past to so analysis of temporal environmental changes become available with multi-period aerial photographs. The Research Center for Humanities and Social Sciences (RCHSS) of Taiwan Academia Sinica conserves and digital scans numerous historical aerial photographs and films continuously. We can’t know where the photographs were taken, which means the great amount of image data is useless if without geo-referencing information. The amount of photographs is too numerous to be processed only by manpower and the original interior parameter of these historical images disappeared after digital scanning, the probability of digital image processing is still feasible. We use computer vision of digital image processing to show the feasibility and efficiency of dealing with the large quantity of historical aerial photographs
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