Intruder deterrent system

1. An intruder deterrent system, the system comprising:

at least one node having a curved or domed surface and comprising a Coanda-effect lifting system that comprises a motor-driven fan configured to direct air downwards over the curved or domed surface; and

at least one strobe light, at least one of said nodes having an intruder-detecting sensor, wherein the system is configured to flash said at least one strobe light and to lift said node off the ground via the Coanda effect lifting system on detection of an intruder by said sensor to deter said intruder.

2. An intruder deterrent system as claimed in claim 1 comprising a plurality of said nodes, at least one of said nodes having a said intruder-detecting sensor.

3. An intruder deterrent system as claimed in claim 1 wherein one or each said node has a said strobe light, and wherein the system is configured to flash at least one of said strobe lights on detection of an intruder by said sensor to deter said intruder.

4. An intruder deterrent system as claimed in claim 1 , wherein a said node is portable and battery powered and has a wireless communications device to enable the device to communicate with one or more other nodes of the system.

5. An intruder deterrent system as claimed in claim 1 wherein a said node has at least two said strobe lights and is configured to flash said strobe lights in synchronism said that no more than one of said strobe lights flashes at a time.

6. An intruder deterrent system as claimed in claim 1 comprising a plurality of said nodes, at least one of said nodes having a said intruder-detecting sensor, wherein said nodes are configured to communicate with one another such that said strobe lights of a plurality of different said nodes flash in a coordinated pattern.

7. An intruder deterrent system as claimed in claim 1 having a plurality of said sensors distributed over a plurality of different said nodes, wherein said nodes are configured to communicate with one another such that said strobe lights of a plurality of different said nodes flash, and wherein operation of a said strobe is dependent on a spatial distance of the strobe from a said sensor detecting said intruder.

8. An intruder deterrent system as claimed in claim 1 wherein said system is responsive to a control unit for selective deactivation of all or a part of said system.

9. An intruder deterrent system as claimed in claim 1 further comprising a control computer in communication with said nodes to determine spatial location of said nodes and to provide a user interface responsive to said determination to indicate missing areas of coverage of said system.

10. An intruder deterrent system as claimed in claim 1 wherein a said node has a beacon mode to provide user feedback on one or more of: an operational status of the node or system; node location; and node or system coverage.

11. An intruder deterrent system as claimed in claim 1 wherein a said node includes an infra-red beam to locate the node and/or to illuminate an area of coverage of a sensor associated with the nodes.

12. An intruder deterrent system as claimed in claim 1 wherein a said node has a plurality of said strobes and a plurality of said sensors, distributed circumferentially to provide selective coverage of a range of azimuthal angles about the node.

13. An intruder deterrent system as claimed as in claim 12 wherein one or both of said sensors and said strobes are angled upwards.

14. An intruder deterrent system as claimed in claim 1 wherein a said node is mechanically configured to be self-righting.

15. An intruder deterrent system as claimed in claim 1 wherein a said node further comprises means to physically tag a detected intruder for later identification.

16. An intruder deterrent system as claimed in claim 15 wherein said means to physically tag said detected intruder comprises means to spray said intruder with fluorescent material.

17. An intruder deterrent system as claimed in claim 1 wherein at least one said intruder-detecting sensor comprises an acoustic sensor.

18. An intruder deterrent system as claimed in claim 17 wherein a said node having a said acoustic sensor is configured to selectively detect an acoustic signal indicative of digging or similar ground disturbance to detect said intruder.

19. An intruder detection deterrent system as claimed in claim 1 comprising a set of said nodes, each said node being configured as an intruder detection node, each said node comprising a physical housing for deployment by placing on the ground, a battery powered microprocessor, wireless communications system for communicating with other nodes and/or a base station, and an alerting system for providing an overt or covert alert, such that the nodes of the system are deployable by dispersing over an area of ground to protect said area of ground from intruders.

20. A method of protecting an area of ground from intruders, the method comprising:

providing a system as recited in claim 1 ;

deploying a plurality of said nodes over the surface of said area of ground such that said nodes are in wireless communication with one another and/or a base station;

detecting an overt or covert alert from one or more of said nodes to detect a potential said intruder.

21. A method of deploying nodes of an intruder deterrent system as claimed in claim 1 , the method comprising dropping said nodes or ballistically projecting said nodes over a range of spatially distributed locations.