Ferocious Aardvark wrote:
snip
There's three images, the two replay images and the original side on image of the live in play which is used to triangulate the images, though 3 angles is not ideal I completely agree, it's all I had to work with. The software isn't published and is something I'm working on in conjunction with a field leader at my institution so I can completely understand people not considering it credible if you wish to do so!
I can't go into too much detail (as I'm sure you understand, with it not being published) but it works, in a very basic form, by pin pointing an object and following it's path from differing angles, of which there was 3 but ideally could have done with 4.
In this circumstance the object was the ball, the front and reverse angles provided the trajectory in an 'x plane' whilst the side on angle provided a 'z plane', I had no 'y plane' to work with due to no angle from the top (spider cam would have been perfect in mapping any mid air movement the ball made and I could have actually provided a clear projection of the ball).
As it were I could only work out the frame in which the object passed a certain point. By analysing the flight of the ball from the side angle, until it went out of view, I could apply a simple SDT algorithm and find a time frame of which the object would have passed the point. By then comparing it against the front and rear angles and applying the same SDT algorithm you can get this point more accurately (I had to speed the replays up into real time by comparing the flight of the ball against the real time side angle which was a massive pain).
When I had found the frame which the ball crossed the plane of the points I plotted the line of the posts indefinitely and compared the relative position of the ball, which was outside the line of the posts. I completely understand what you're saying about the relative position of the camera but I don't think it makes too much difference in this circumstance, unless my calculations are way out and the ball is at least a couple of metres before or past the point of where I think it should be, which I don't think any error would be that large.
When I say the software is like hawkeye, it's in that it uses differing angles to analyse flight of an object, it doesn't use the same algorithms and as you've quite rightly pointed out a flight projection isn't possible due to the lack of angles but you can perform an accurate SDT object analysis from the 3 available angles.
Please do point out anything that you think may be wrong in the analysis as it'll help to hopefully get a more accurate and conclusive result. I just wish there was an angle from the other side or top as well as I could map that without any problem!