direction finding


I'm looking for some smart way of finding the object location. I don't need exact point, only an angle - direction from given point. The object is located on a plane and we can put on it some sensors/tags (active, but better passive). The object will be placed maximum 30cm (11 inches) from the center.
I'm looking for it quite long and I cannot find any easy and clean solution. Did I miss something?

  1. use a ping sensor upon a 360° servo, create a radar.
  2. put floor sensors in the plane
  3. use 2 ping sensors from different position and you can cross the direction lines to get the point