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iOS App Acoustically Measures Distances Up To 25 Meters
n01 writes "A recently published app for the iOS platform uses the propagation of sound waves to measure distances of up to 25 meters in a dual device mode. The technique works through repeatedly sending a chirp signal from the master device to which the other (reflector) device synchronizes itself and then replies in a similar fashion. A novel combination of techniques has been engineered to enhance the robustness in noisy environments, such as using an optimum-autocorrelation-signal and semi-automatic frequency calibration together with an averaging over multiple cycles."
http://wiki.laptop.org/go/Distance
That's not very impressive. Anyone who has two devices that are syncronized to a common timing source (which most cell phones are) can accomplish this. You just say "I started transmitting at x and you received it at y. x-y/speed of sound at sea level = your result. Now if it could be done with one device, and use doppler effect,etc., to map out the room and roughly what's inside it (like in Batman) then we'd be getting somewhere.
#fuckbeta #iamslashdot #dicemustdie
I thought this was going to be a cool sonar thing- you'll need 2 iphones? get a tape measure...
Weapons Officer: "Captain I can't get a fix on the enemies position."
Science Officer: "We could try using an optimum-autocorrelation-signal and semi-automatic frequency calibration together with an averaging over multiple cycles."
Captain: "Good idea."
Me at home: "Who makes up this stuff."
Some humans can learn echo location[1], but just wondering if we could have an app that sends clicks and chirps and processes the echos and creates a picture or 3D model.
But it might need two or more "ears" to quickly build a 3D image of the environment.
[1] http://www.youtube.com/watch?v=qLziFMF4DHA
http://www.youtube.com/watch?v=GYWpxmcHTOc
Because such an app already existed for PocketPC (That'd be Windows Mobile):
http://nerdipedia.com/tiki-index.php?page=Sonar+CE
Oh, and desktop PC:
http://nerdipedia.com/tiki-index.php?page=Sonar&structure=index
I hear there's a flashlight app for iDevices, too - Slashdot should really look into that. It's magical.
This didn't seem to do that good of a job, but was 2 years ago.
* Sonar Ruler, By Laan Labs: http://itunes.apple.com/app/sonar-ruler/id324621243?mt=8
* http://thenextweb.com/2009/08/20/amazing-iphone-app-lets-measure-distance-echoes-works/
Happy measuring!
http://stephan.sugarmotor.org
"Please note that while the resolution of the measurements may be as low as 1mm, the precision usually is not. While I have taken great care to make the app as reliable as possible, there are simply too many factors affecting the measurement process and the precision. That is why I want to be clear about one thing: there is absolutely no warranty that the measurements taken with Acoustic Ruler Pro are correct"
Another good example of incorrect usage of the word precision. In this case, the method is actually quite precious, as in measurements are very repeatable. What the author meant is that the accuracy is not very good. I tried out the app just now, at the range of 22 inch (width of my monitor), it under estimates the distance by 1 inch; and for something half an inch apart, it over estimates by over an inch. It is possible to measure the non-linearity using a control setup, but the result would be largely useless, as measurement of different items requires placing the item near the source and receiver, and this will likely change the acoustic behavior of the environment and affect measurement accuracy.
This Sig is removed due to factual inaccuracy
When I see the word 'novel' applied to techniques that have been used for decades, I smell 'patent lawyer'. And be extension: astroturf.
Signal processing techniques applied to sonar (whether active, passive or beaconed) including signal correlation, spectral adaptation/equalisation, and filtering are standard fare in this field.
Maybe by novel they mean "on an iPhone"?
That being said, there is nothing that says this won't work - as it worked extremely well 20 years ago on dedicated systems with far less processing power. (Those systems, however, used multiple arrayed transducers and tailored beam patterns to significantly reduce the effective noise floor.)
About 20 years ago, I had a hand-held device roughly the size of a smart phone but twice as thick that did distance measuring all by itself. It was infrared and as I recall, it was something like $25.00 from Rat Shack or Home Depot or some place like that. A 30 foot tape measure is about $8.00 and works a lot better.
Nothing worthwhile ever happens before noon
One suspects that the primary use case for this application is not, "Hey, we need to measure this, let's go get two iPhones!" It's "Hey we need to measure this and happen to have two iPhones, but no tape measure." Most people carry their phones around with them all the time, but unless they're contractors don't carry tape measures. The point of near ubiquitous mobile computers is that you can use them for lots of things. This is a cute and clever thing that you can now use them for.
I don't need a million points of light, just two points of multi-mode fiber and a 10 Gig-E router.
So Slashdot can't report on anything, ever, if it's for sale somewhere. Got it.
Is there any benefit to moving to ultrasonic frequencies? Other than making it inaudible (so you don't bother people but maybe dogs!), would this improve the resolution? Does the range decrease? Do consumer level devices cover such a broad spectrum?
By the way, has anyone made an iOS or Android App that can record in the ultrasound (or infrasonic) ranges and change it so that we can listen in audible ranges? Might be neat to see/hear what the bats are doing!
Also, how DO bats build up a good 3D map of their surroundings using just one "speaker" and two "microphones"? Do they send out beams or are their ears swiveling? And, with the limited amount of computing power on a smartphone, would it be able to duplicate it? A bat's brain doesn't seem particularly large and they are doing this FAST (on the fly, ha ha).
No, the primary use case is "oh, this is nifty, let me play with it". The accuracy is nowhere near good enough for any measurement that actually matters.
Tape measure? Where do I get that app?
The shepherds did so well protecting the flock that the sheep no longer believed that wolves existed.
You could measure room wall lengths close enough for basic estimates on how much paint to buy or fence length estimates and such where you don't need cut to fit accuracy.
Persistent Volume manager for Kubernetes - https://github.com/dwimsey/openshift-pvmanager
I strongly prefer empirical methods in this case.
"... and more and more now there are all kinds of electronic goodies available" -- Pink Floyd 1972
You can get enough accuracy for buying paint and fence length by counting your steps.
You have to walk from one end of the measurement to the other whether you're counting steps or just putting the phones in place, but you don't have to walk back to the starting point to pick up a phone, however, so the entire process is easier and faster if you just count steps.
The prostitute that laughed at you and said "that's not even four inches" doesn't count.