Robocup field distortion calibration with variational image registration

The Global Vision System is widely used among teams of Robocup F180 (Small Size League). This architecture as well as the 1-hour preparation time limit before each match poses strict requirements to the accuracy and efficiency of the calibration method against pitch field distortions. Because of the curvature-preserving feature of these distortions, we propose a brand-new image registration approach, which does not require calibrating the camera, but directly maps the distorted image to the real pitch. While this method substantially simplifies the pre-match manipulation, it also maintains high accuracy - our experimental result shows that, with double camera, the mean error ratio is limited within 0.22%, accurate enough for Robocup matches.