VOL Testing Process

The assessment of virtual offside line systems, to be used in conjunction with VARs, shall be conducted at two separate stadiums and a system has to pass the test at both venues in order to achieve certification. The test method itself involves two distinct test blocks aimed at determining the accuracy and the repeatability of each provider.


The first test block is based on two-dimensional markers and a wider-angle perspective, thus verifying that the system is capable of correctly placing an offside line across the entire field. Key challenges in this test block include the field’s topography and the various camera angles. The second test block, a three-dimensional test, uses a marker suspended in space and tighter camera angles. This assesses the system’s ability to calibrate and capacity to pinpoint an exact location across several cameras in a more match-like scenario. As a result, this addresses the issue of individual body parts suspended in an offside position and, at the same time, player occlusion.

How the lines are created and measured

The offside lines shall be tested in a football stadium with a minimum broadcast set-up of four cameras (main camera, 16M right, 16M left and a tactical high-behind camera) recording in broadcast quality to an outside broadcast (OB) van or equivalent. Tests cover the entire field in order to ensure full pitch calibration and all providers must be able to draw correct offside lines on three of the main cameras (and possibly the tactical camera when one of the others is not available). The still images are then used to evaluate positioning vis-à-vis the ground truth. Providers must either pass all scenarios or meet the scoring requirements stated to obtain approval.

Handbook of Test Methods

The research that went into the development of this manual has highlighted some of the limitations that today’s technologies and realistically available site equipment have with regard to measuring virtual offside lines. Overlaying images and detecting exact points, even in high-resolution images, can have a degree of uncertainty depending on which pixel is selected. As with all measurements, there is a (known) degree of error, which has been considered when selecting the requirements.

The updated test method aims at reducing the degree of error in the testing by minimising the human error in the analysis stage. The latest method uses qualitative analysis to determine whether the virtual offside line falls within a predefined set of tolerances. This therefore reduces the source of human error previously present, particularly with pixel selection during quantitative analysis.

For the detailed test protocol with more information about the test set-up, the methods and the requirements, please find the link below:

FIFA Accredited Test Institutes

The tests are performed by the following accredited, independent test institutes and certified systems are listed here for end-user guidance.