Does anyone know of any good/easy reference to guess an average "field of view" (FOV) for outdoor security cameras? Or is this not possible at all?

I realize that a combination of the kind of lenses and microships that different cameras have, result different FOVs (there are calculator for this: http://www.sweeting.org/mark/lenses/cctv.php), but I wonder if there is anyway to tell an average measure (in projection). I am surveying private cameras looking at public spaces and wanted to have an idea of how their FOVs can be drawn up on a map.

Any help, at all, would be most welcome.

Cheers,

Rodrigo.