Why not detect the intruder as they cross the perimeter, you could use
multiple light barriers to detect the entry point and focus the camera
on that. Alternately use a light barrier to detect intrusion and then
scan/record the yard for a period of time before reverting to detection
mode. Or for the really brave of hart, sink sensors in the ground and
use induction comparison i.e. like the surface of a touch screen. The
latter is probably not practical due to the effects of weather.

If cost is not the issue, I'd recommend multiple cameras capable of
detecting changes in the scene.

BTW, ever thought of an electric fence or a dog :-)


Gareth

Project & Operations Manager, STB Systems Inc.
Tel: +44 1232 258402, Fax +44 1232 319970, WWW Page: www.stb.com