Best way to track a flying object/Indoor object tracking.

I suspect that even with devices installed in the quadcopter what you want to do will be difficult if not impossible with DIY resources.

I don't think a GPS receiver in the 'copter would give you a sufficiently accurate position (if it worked at all indoors) and that is probably the easiest solution.

The alternative is some sort of radar/sonar system. But how would a "ground based" device "recognize" the quadcopter in order to measure how far away it is?

...R