I have 'k' fixed cameras, I have their geo-coordinates,
and when I receive a geo-location coordinate of an object from a radar I need to PTZ track the detected object using the camera nearest to the object. 

calculating distance of all objects detected from each camera to find the nearest one is slow when the number of cameras is large. 

I need to reduce latency, and am thinking of introducing 'n' points located adequately, (grouping cameras into n groups) to first decide which group of cameras to begin calculating for. 

I don't know how to find these n points, and what a good number for 'n' is?