This publication describes techniques of using an ellipsoidal projection for correcting image distortion caused by wide-angle cameras. Two-dimensional (2D) cartesian pixel coordinates of an image taken with a wide-angle camera are first back-projected to three-dimensional (3D) spherical pixel coordinates (e.g., onto a surface of a 3D sphere) using a focal length of the camera. The 3D spherical pixel coordinates are then projected to 3D ellipsoidal pixel coordinates (e.g., onto a surface of a 3D ellipsoid). Major and minor axes of the 3D ellipsoidal pixel coordinates are defined according to a determined face orientation within the image. The 3D ellipsoidal pixel coordinates are then projected to 2D cartesian pixel coordinates to arrive at a distortion-corrected 2D image.
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Shih, Yichang; Liang, Chia-Kai; and Lau, Peng-Ho, "Techniques for Wide-Angle Distortion Correction Using an Ellipsoidal Projection", Technical Disclosure Commons, (June 08, 2020)