Estimating deformation factors of planar patterns in spherical panoramic images

The transformation between a planar image and a planar pattern is commonly described by a homography. However, a homography cannot express the exact relation between a spherical panoramic image and a planar pattern. In this paper, we propose a new method of parameter estimation for locating planar patterns in spherical panoramic images. First, we estimate transformation parameters which express how much the target object is scaled, translated and rotated in the spherical panoramic image. Then, we project the planar pattern onto the center of the spherical panoramic image. The center-aligned pattern is used to estimate the transformation parameters. The parameters express the geometric relation between pixels in the spherical panoramic image and pixels in the planar pattern. Our proposed estimation process decreases the error of pattern matching caused by the heavy spherical distortion. Experimental results show that the failure rate of matching is significantly reduced.