Originally Posted by JackB1
Thanks for the reply. I think the bigger issue though is how u have to estimate the spot where the serve hit the court. I tried moving the spot around just a little bit and got readings as much as 10 mph apart. That's just a bit too large of a variance to make the app useful.
As explained in the previous comment, moving the spot where the ball hits (lands on) the court horizontally almost doesn't have any effect on the speed.
Moving the ball 1 foot in the vertical direction does by 1.6 miles of error (see previous comment). So the 10 miles you talk about would mean moving the ball more than 6 feet from it's real landing location. In normal circumstances you should be able to guess the balls location within a foot of its real location (especially if its close to the lines).
I have tested it with real videos from the australian open where the professional radar gun shows the speed so i was able to compare. All the calculations i did where within 2,5 miles of the radar gun's speed except for 1 out of 10, I suggest you try it your self at a pro tournament.
It would still be really nice to overcome the 'human error' of this step and i do have a way to reduce it! the idea is to overlay the 4 corners of the servicebox and then transfer the balls location from 1 dimension to the real dimension of the court. I am confident that this will be quite accurate. I hope to come with an update with this functionality, but give me some time
Anyway i think the App, as how it is, is the most accurate we can get with today's smartphones. And i still think the 2.5 miles error is not bad at all!