How can I determine a camera's position based only on video?

[cdave]

I need to be able to track the postion of a camera. The camera is mounted in a fixed position, but has the ability to pan, tilt & and zoom. Without adding sensors to the camera head, I need to know the amount that the camera pans, tilts, and zooms, based on the video coming out of the camera. The camera would be focused on a football field, so there are reference marks available, but there would also be people on the field. This also needs to be in real-time (30fps). Any idea's?
I have included an image of what the camera would typically see.
Thank you,
-Dave

[cld]

Dave,
One idea would be to use OCR to read the yardage on the field. Since the numbers are always relative to the line, you could use edge detection to find the line location and then setup a ROI relative to the line to search for the Numbers. Once you have this, you could find the location of the number in you FOV to determine where you camera is centered.
I hope this helps!
Chris D
NI Application Engineer