Slashdot Mirror
Why Detecting Drones Is a Tough Gig
An anonymous reader writes with a link to some interesting commentary at Help Net Security from Drone Lab CEO Zain Naboulsi about a security issue of a (so far) unusual kind: detecting drones whose masters are bent on malice. That's relevant after the recent drone flight close enough to the White House to spook the Secret Service, and that wasn't the first -- even if no malice was involved. Drones at their most dangerous in that context are small, quiet, and flying through busy, populated spaces, which makes even detecting them tough, never mind defeating them. From the article, which briefly describes pros and cons of various detection methods: Audio detection does NOT work in urban environments - period. Most microphones only listen well at 25 to 50 feet so, because of the ambient noise in the area, any audio detection method would be rendered useless at 1600 Pennsylvania Avenue. It is also too simple for an operator to change the sound signature of a drone by buying different propellers or making other modifications. It doesn't take much to defeat the many weaknesses of audio detection.
I assume detecting the RF signature of the transmitter controlling the drone is the best way.
Of course there are these problems:
1. There are many signals on the bands used for RC.
2. It is possible to build an autonomous drone.
3. In these days of software defined radio, people can spin up non-off-the-shelf, non-standard radio control systems.
Omne ignotum pro magnifico.
What about an autonomous drone which is just flying to certain GPS coordinates and then detonating? Or even just using inertial guidance and image processing?
Awesome furniture, accessories and cabinetry in Santa Rosa, CA: http://humanity-home.com/
I just don't buy that audio can't be used. With an array of high quality microphones spread over an area fed into a software radio and some pretty hefty computing power you should be able to look for the rhythmic audio that your typical copter type drones will generate. Because even if they change the size and shape of the rotors all that does is change the frequency not the amplitudes you will see from the rhythmic action.
With some proper math and the right computing power you should be able to identify drones pretty rapidly with fourier analysis and the same microphone array could use Doppler effects to calculate position, and the directional vector. Combine this with some systems to double check such as heat, RF and conventional high band doppler radar and you should have a system that will get 99% of the drones and even provide targeting to a shoot down type system.
The key here is you need some pretty dam good microphones spread over a pretty large area feeding into a pretty massive computer array. It wouldn't be cheap or easy. The easy thing is use a doppler radar system that cross-checks it against RF emissions to eliminate birds. But IMO the best system would use all three, high band doppler radar, RF emissions and audio (and maybe even heat). With three cross checks you should be able to get pretty good accuracy.
It's actually a very hard problem - because you have to detect who is receiving the signal, not who is sending it. The sender can be far enough away to bleed into the background radio noise.
The more expensive drones can receive GPS signals and follow a preprogrammed course.
Either way, it may sound easy on the surface, but it's not.
Taking into account size, altitude, a simple sonar detection fence works the best. Sonar units firing vertically completely surrounding the facility to detect all incoming flying objects and then the use of suitable rapidly decomposing shot fired from a compressed air shotgun to bring it down, this to prevent excessive collateral damage of the human variety. Birds are another matter, they will end up killing all that cross the sonar detection fence. So that mess will need to be continuously cleaned up. High altitude drones require additional deployment of sonar detection equipment firing at an angle over the structure to be protected. Heavier drones of course means accepting collateral damage, screw the public save the rich and greedy and their political puppets.
Chaos - everything, everywhere, everywhen
The drone doesn't actually have to transmit anything. It can also be made to just have a receiver.