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Smart phone IRS ?

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Smart phone IRS ?

Old 24th Feb 2015, 04:11
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Smart phone IRS ?

Just a hypothetical one (after a conversation in the pub last night)

Given that the latest smart phones come with accelerometers and gyros, if someone had the inclination and knowledge, would it be feasible to program an app to work like an aircraft IRS ?

I'm imagining putting in my start lat/long in (manually or via phone gps) and watching it give me the phone's current position, velocity and attitude.
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Old 24th Feb 2015, 05:15
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They've already made artificial horizons using the gyro but in my experience they don't work all that well.
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Old 24th Feb 2015, 05:16
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I'd suspect it's feasible. I've already got a psuedo ADI/HSI app thing that i've tried for fun up in a local rental. Kinda worked.

The problem I think is I don't know if the gyros/accelerometers are accurate enough to actually record changes in in positions rather then just changes in rate/acceleration.
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Old 24th Feb 2015, 05:57
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Thanks guys, it was an AH app that got me thinking about this. I mean the processing power in these modern smart phones has to out do the computers on the earliest irs systems.

If it was accurate, would it make navigation apps (eg. imaps/google maps) on the phone less battery-intensive.

GPS depletes my battery so quickly.
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Old 24th Feb 2015, 07:58
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Processing power most likely is not the problem at all. It might be the drift rate of those gyros, which appears to be very high. I used one AH app on my iphone for a short 45 minute flight, at the end of that sector (back at the gate) it was off by more than 30.

I agree about the GPS drain, but you can of course offset that by using an external GPS mouse with bluetooth LE connection. But the biggest drain on the battery is usually the display anyway.
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Old 24th Feb 2015, 08:25
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A few thoughts: first of all you'd most likely want a dedicated box for that task, not your phone/iPad that also runs tons of other applications, which could introduce conflicts. Just like you don't use Flight management system computing resources to stream videos for the in-flight entertainment system. Further, you'd probably want the thing hooked up to additional sensors, eg. airspeed, maybe a more reliable gyro that is installed in a fixed position, properly calibrated; etc. Inexpensive, commercial-off-the-shelf technology, not certified, suitable for use in an experimental a/c, at your own risk, something like this: iEFIS
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Old 24th Feb 2015, 08:40
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Don't think I'd ever use it (at it currently tech level) for flight. Maybe in the car.

But just wanted to see if others thought it possible with current smartphone technology.
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Old 24th Feb 2015, 09:00
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Usability of apple iPhones for inertial navigation systems. - ResearchGate

people have tried this, and the results vary, depending on the device.
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Old 24th Feb 2015, 09:09
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Thanks deptrai

I just looked for inertial navigation/reference on the App Store. (With no joy)

Cannot imagine the level of calculation and coding required to make it work. Some real smart people out there.

Last edited by flying apprentice; 24th Feb 2015 at 09:10. Reason: Think I will turn auto correct off forever
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Old 24th Feb 2015, 09:58
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Im not familiar with the technical intricacies of smartphones, but Id assume another issue is that hardware components may vary, even within what is sold as the same model, eg accelerometers sourced from whoever is cheapest and can deliver. These hardware differences may affect software, and if a team of cabable programmers wanted to launch a commercially feasible product for semi-professional use, they would probably need assurances that all critical hardware components won't be changed for a few years. The way consumer product supply chains work, that seems unlikely.
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Old 24th Feb 2015, 10:32
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not your phone/iPad that also runs tons of other applications, which could introduce conflicts.
Point of order (at least when it comes to Apple iPhones and iPads).

Unlike traditional Operating Systems, when it comes to said devices, unless you've been an idiot and "rooted" your Apple phone/pad, all apps run sandboxed.

This is an inherent part of the Apple phone/pad security model that apps cannot interact with each other or in unauthorised ways with the underlying operating system.

When you submit an App to the App Store, you list the external privileges your App requires (e.g. use of GPS), and Apple verifies your App does what you says it does and does not attempt to escalate beyond your declared uses.

Now, whether you'd use a phone/pad for primary aircraft navigation is another question...
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Old 25th Feb 2015, 12:54
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> Usability of apple iPhones for inertial navigation systems. - ResearchGate

to quote from the full text of the paper:

"Fluctuation and jitter contribute to the inaccuracy and make an exact determination of the velocity and the position difficult. Due to the necessity of filtering the data stream, further losses of information arise and increase over time. [...]
However, the tests show that even with the use of filters it is challenging to build a precise INS using sensors from common devices because of their inaccuracies and high error rate.
The results show that the iPhone 4 can provide tolerable results for a short time, but then the deviation becomes too high because of the error rate."

Or consider this... the accelerometers and gyros are designed and optimized for mass market consumer applications (read: mobile devices) in terms of application, technical specification and - most important - cost, which is typically less than $1 for each sensor. (My company works in this field.)

Any IRS application most likely needs sensors build to different specifications, at a different cost. Or, to quote the paper again, "By examining the raw accelerometer data of the iPhone 3GS and iPhone 4, it becomes clear that low-cost MEMS are used in both."
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