How to count all RFID in a small room?

Question

RFID

Good afternoon.
There is an event. All visitors have RFID badges. You need to count how many badges are in which room without scanning every visitor every time.
Tell me, who knows, pls, are there such systems on the market that are hung somewhere on the ceiling and simply count how many RFID tags they see in a radius?

Answer 1

The label is read from a very small distance. Accordingly, only through some frame it is necessary to keep records.

Answer 2

Rfid comes in different frequencies. There is rfid for warehouses. Frequency 960 Mhz, reads at a distance of up to 10 meters. Tags cost ~15 rubles. reading equipment: reader + 4 antennas ~150 000 rub.
Here, depending on what task, if you count the visitors, you can solve the problem using a computer. vision - put the camera under the ceiling and count how many people are in the frame.
What counting accuracy is needed?

Answer 3

An RFID card, at its core, is a wireless magnetically powered chip (what smartphones are currently charging with). And now remember at what distance smartphones are charged.
As an option - to consider "sheep" as third-party software, and then it is necessary that the entrance and exit be with a reader and visitors do not crowd into open doors.