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GS-RANSAC : An Error Filtering Algorithm for Homography Estimation based on Geometric Similarities of Feature Points
Kiheun Song, Myung-Duk Hong, Geun-Sik Jo
http://doi.org/10.5626/JOK.2020.47.3.283
Augmented Reality (AR) is intended to generate information by displaying augmented objects on real-world objects. AR is essentially used to calculate the coordinates of augmented objects, for which a homography estimation method involving two images is generally used. In homography estimation, the RANSAC (Random Sample Consensus) algorithm is used to select the four most appropriate pairs of feature points extracted from the two images. However, conventional RANSAC algorithms cannot guarantee the geometric similarity of the inter-image locations of the feature points selected randomly. In order to resolve this conundrum, we propose an algorithm to evaluate the geometric similarity of inter-image locations of feature points. The proposed algorithm draws tetragons of feature points on each image. Then the algorithm determines if the tetragons are similar in the order of vertices and the range of internal angles. The experimental results show that the proposed algorithm decreases the failure rate by 8.55% and displays the augmented objects more accurately compared with conventional RANSAC. We improved the accuracy of augmented object coordinates in AR using our proposed algorithm.
Estimating Geometric Transformation of Planar Pattern in Spherical Panoramic Image
A spherical panoramic image does not conform to the pin-hole camera model, and, hence, it is not possible to utilize previous techniques consisting of plane-to-plane transformation. In this paper, we propose a new method to estimate the planar geometric transformation between the planar image and a spherical panoramic image. Our proposed method estimates the transformation parameters for latitude, longitude, rotation and scaling factors when the matching pairs between a spherical panoramic image and a planar image are given. A planar image is projected into a spherical panoramic image through two steps of nonlinear coordinate transformations, which makes it difficult to compute the geometric transformation. The advantage of using our method is that we can uncover each of the implicit factors as well as the overall transformation. The experiment results show that our proposed method can achieve estimation errors of around 1% and is not affected by deformation factors, such as the latitude and rotation.
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