I think it's important to clarify if the area is a shopping market or a much bigger airport hall. Not only for the area but also for the lower ceiling and presence of metallic objects (shelves) that could interfere.
One basic technique is to fix a RF emitter to the person/ object (it can emit a short burst every second or so). If you place at least three receivers and can measure the signal strenght with enough accuracy, some basic mathematics will tell you where the source is. Again, this technique works the best in an open space with little electrical perturbations. For different targets, you need different frequencies, and your receiver will also need to be multifrequency.
If you cannot afford a transmitter to be attached to the target for the need of batteries and need a passive transponder, like an RFID tag, then I think (I'm not sure) that the range is very short (a few meters) so you can easily need thousands of them attached to the floor, isn't it a little bit crazy?