The aerial three-linear push-broom camera, with its simple and rational structure, enables low-cost and rapid acquisition of high-resolution aerial images over large areas. It plays an irreplaceable role in agricultural surveys, forestry investigations, and large-scale topographic mapping. Particularly in China, the ongoing national natural resource surveys in regions such as the northwest and northeast have provided unprecedented opportunities for the application of aerial three-linear push-broom cameras. However, we have identified that stereo measurements based on Level 1 images suffer from issues such as accuracy loss and low efficiency in object points back-projection. To address these challenges, this study introduces a real-time epipolar fitting algorithm for local scenes and a fast back-projection method guided by a 3D spatial grid. The epipolar fitting algorithm dynamically adjusts image orientation based on flight direction (κ), effectively eliminating edge vertical parallax and improving stereo viewing quality. The fast back-projection algorithm constructs a 3D grid to store the coordinates of corresponding image points, enabling efficient retrieval of image coordinates for any spatial point through localized search. Validation experiments conducted on eight datasets demonstrate that the proposed methods significantly enhance epipolar image quality and stereo mapping efficiency, reducing vertical parallax by an average of 80% and increasing back-projection speed by at least 2.6 times relative to conventional
