Detecting camera position based on more image targets placed on the floor

Hi,

What is the best way to detect the camera position in a room, based on a series of image targets placed on the floor at predetermined positions?

Camera would look down and see only some of the image targets (like 4 or 6).

I'm using Unity.I saw the user custom images can have a list of up to 5 images and it notifies you when tracking one of them. I need more than 5, probably around 16 or more.Or I can add more cameras, each trying to track one image and then make an average from the positions of those that are currently detecting their markers?Or if the multitarget would have worked with a different shape than a box (planar).

So, please give me a piece of advice on how to start this.Thanks!Alex