abu13
Well-Known Member
What if the player who strikes the ball does so in a plane that is not 9O degrees the to the camera?
That exacerbates the problem about identifying in a 2D frame the moment when the ball is struck, and what is the relevant moment for the offside comparison? When the boot strikes the ball, or when the ball leaves the foot? What is to stop the operator using different criteria in every game?
Then once you have the frame, how do you compare the position of players who are not inline with the camera. Drawing the line across the pitch is straightforward. Anyone can do that in microsoft Paint. I've done it loads of times, but then you have the problem of body parts which are are at different heights and this distorts the view when you are not inline.
To illustrate this effect:
We know that Stones cleared the ball on the goal-line as per inline camera footage, but look how it appears when it is viewed from a different perspective.
As far as I know, VAR are not correcting marginal offsides calls for the viewing angle and relative heights of bodypart and reference line when the ball 'is struck'. It matters not when the camera is inline, but it does matter when it isn't, and frequently it isn't.
There are 2 sources of error with VAR offside calls:
1) Establishing the moment when the ball is played because there is no single moment, and in practise it's not so easy to capture anyway
2) Distortion of the like we see above when player's goal-side body-parts are at different heights, and the view is at an angle
I maybe wrong about the 2nd point, but if this effect exists for goal-line assesments at an angle, then I think it should also be applicable for offside calls. Isn't the goalline clearance we have in the image above directly analagous to a line across a pitch and two player's body parts which are at different heights to that reference line?
The only mitigation is that typically the angle is small. They try and select an image that's relatively inline, but they are never directly inline. Look at the size of the error that this angle introduces.
Regarding the ball, in my opinion as long as the player passing the ball has the ball connected to his foot (or appears to have) then the frame can be used, don't forget i believe the attacking team should have the advantage here.
I understand what you are saying about camera angles but again with the money in the game I can see no reason why a series of cameras could not be fitted across the entire length of the pitch to assist with the capture of images.
7-8 years ago there was no goal line technology but look at the difference this has brought about.
Who is to say that in the next 5 years the players shirt don't incorporate a small GPS chip that can measure at any moment the proximity of a player to the goal line and automate the process that way. Obviously this could not be rolled out through every level of the game but anything is possible if they had the will to change things for the better.