Author Options:

Gunshot Locator using iphones? Answered

Will someone please make an app for our troops- one that uses multiple iphones to acoustically triangulate the location of the source of a gunshot and multiple gunshots so that each phone user could hold their phone up with a real time image and see an overlay of the exact position of the shooters.  

It's too expensive for the military to implement,  but the kids can have phones.  

Not sure who this guy is shooting at, not sure if he lived. http://www.break.com/index/soldier-films-himself-being-shot-by-taliban-2373200


Interesting idea. Phone has gps. If an app automatically phoned in to a central computer when shots were fired, the computer could work out distance using speed of sound. With 3 or more phones, you could extract location from that. Omnidirectional mics should work for this method. I suppose accuracy would be contingent upon how far apart the "ears" of the system are.

The speed of sound is only 1126 feet per second. If you had mics 112 ft apart, that would be a sound delay of up to 1/10th second.

As far as processing power, it shouldn't be any harder than getting location on a gps from speed of light transmissions from 3 satellites. It should be easier, since sound is so slow.

Is there any time delay on a cell transmission? This could be an issue for working out delay due to speed of sound.

Such a system could also advise you of position of your buddies to avoid a friendly fire incident.

The military has systems like this but they are big and bulky and typically mounted in a vehicle of some kind. Part of the reason these systems cost so much is the unidirectional microphones used in them. These mics are pointed in a specific direction and will only pick up sound from that direction. The microphones on any cell phone are omnidirectional meaning they pick up sounds from all around. So there is no way to utilize them to help give even a general direction of where the shot came from. Not to mention the microphones of all the phones would have to be pointed in specific directions to cover the surrounding area or they wouldn't get a good picture. Then you have the problem of solders standing around out in the open waiting to be shot at so they can figure out where its coming from. I doubt a single or even multiple phones networked together will have the processing power to pick up that split second sound of a shot and triangulate its origin. I think its this reason that solders are not walking around with a small set of microphones on there helmet and a small pocket computer to do the processing. We are getting closer ot that sort of technology but we are not there yet.