Ah, I see. It's measuring the diameter of the IR light. So it's going to be limited by the effective XY resolution of the camera and the diameter of the IR light.
I did a test on the Wii sensor bar calibration screen that shows IR lights as white circles. First of all, the higher the sensitivity setting, the more accurate it gets, but the more prone to IR confusion from foreign sources. That said, the highest sensitivity (5) was only able to detect a change in IR diameter after about 18 inches of movement on the Z-axis. At sensitivity setting 1 it took about 30 inches to trigger the diameter change. I was standing about 4 or 5 feet away in both cases.
For the horizontal position test, I was able to move about 10-12 feet left to right, before it detected any change in diameter between the closer and further IR light. I was standing about 7-8 feet away.
That is not good at all. Move can detect 1-2cm of depth and 1mm on XY.
I did that test because it was easier than figuring it on with math. But since we can't know for sure if that was using the Wiimote to its full potential, let's do it mathematically, using Move's dimensions and accuracy ratings as a guide.
Wii camera effective resolution: 1024x768
Move camera effective resolution: 6400x4800 (
link - look for "tenth of a pixel")
Move's advantage: 6.25:1
One Wii IR light
array diameter: 2cm (estimate)
Move sphere diameter: 4.5cm (estimate)
Move's advantage: 2.25:1
Total advantage (multiplied together) 14.1:1
Since the Wii method of determining horizontal position relies heaviest on depth, we'll take the 1.5cm accuracy rating for Move's Z-axis and multiply it by 14.1 to get 22.2cm, or 8.5 inches, for my guess for the Wiimote's accuracy in terms of single orb depth tracking. The hands-on test with the calibration screen indicated only 18 inches of sensitivity, so we will compare that to the calculated accuracy ratio of 8.5 inches and come away with the conclusion for the Z-axis sensitivity that it is 2.11x better than what the sensor bar calibration test indicated.
So let's take that same magnitude of 2.11x and apply it to the real world horizontal position accuracy results of 10-12ft.
Drumroll....
That's still only 4.7-5.7ft of X positional accuracy.