Virtual lines for offside situations analysis in football

  • Karim Ferreira Lima UNISINOS
  • Rodrigo Marques de Figueiredo UNISINOS
  • Eduardo Augusto Martins UNISINOS
  • Jean Schmith UNISINOS


Offside is one of the situations that is analyzed by the Video Assistant Referee (VAR). However, it has caused some controversy due to the delay in the analysis and definition of the irregularity. This work proposes a method that helps in the analysis of offside situations and also makes it available for nonprofessional matches. Here, image processing algorithms were used to determine offside situations in football matches from TV videos, of course, in accordance with the game regulation. The method includes the image vanishing point identification, camera calibration and the virtual offside line drawing. The method presented good results from 10 videos selected for analysis, with five from the right side of the field and five on from the left side. Among the videos, one was chosen as the basis for explaining the development of the method and demonstrate a situation with a virtual line drawn automatically, therefore determining an offside situation. As a result, the virtual line is identified by the color red when the manually selected player is in offside and green when he is not.
Palavras-chave: Football Offside, Virtual Offside Lines, VAR, Digital Image Processing


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LIMA, Karim Ferreira; FIGUEIREDO, Rodrigo Marques de; MARTINS, Eduardo Augusto; SCHMITH, Jean. Virtual lines for offside situations analysis in football. In: WORKSHOP DE TRABALHOS DA GRADUAÇÃO - CONFERENCE ON GRAPHICS, PATTERNS AND IMAGES (SIBGRAPI), 34. , 2021, Online. Anais [...]. Porto Alegre: Sociedade Brasileira de Computação, 2021 . p. 189-194. DOI: