Wi-Fi off effect on assisted GPS?

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Level 1

9 points

Wi-Fi off effect on assisted GPS?

Wondering if anyone can answer a un-googleable question.

With Wi-Fi off and opening the native iPhone map app there is always a pop up message saying GPS accuracy improves with Wi-Fi on and has a button to go right to settings to turn it on. Okay, I know GPS accuracy is improved while connected to Wi-Fi, but is it improved even when not connected but turned on?

Thinking maybe just having Wi-Fi on searching and locating connections may pinpoint your location relative to Wi-Fi routers and/or hot spots along your route and help with positioning and tracking. I know this would kill the battery but am neurotic enough about my GPS tracking apps to do it anyway.

My experiments with this are inclusive. May seem like a silly question but like I said I'm neurotic about my GPS accuracy. So, does anyone know for sure one way or the other?

Thanks.

iPhone 4S, iOS 5.0.1

Posted on Mar 20, 2012 9:46 AM

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Answer 1

paulcb

Level 6

19,239 points

Mar 20, 2012 10:18 AM in response to sorcc

I see no difference... my iphone puts me in the exact same spot with or without wifi. Unless you're geocahing, does it really matter if it's off a few additional meters?

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Answer 2

Mar 20, 2012 10:26 AM in response to sorcc

sorcc wrote:

but is it improved even when not connected but turned on?

Yes.

WiFi seems to make less of a difference with my iPhone than it does with my Androids. My last 2 Android phones, if WiFi was off, showed me, consistently about a mile away when I was at my office. As soon as I turned WiFi back on, the location was accurate practically to the meter. Mind you, this was a situation where I was stationary.

On the other hand, one of the running apps I use, Runmeter, says to turn off WiFi if the GPS seems in accurate as grabbing location data from a WiFi accesse point when GPS is weak might result in inaccuracy. My tests on this are inconclusive.

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Answer 3

sorcc Author

Level 1

9 points

Mar 20, 2012 10:53 AM in response to IdrisSeabright

I have had the same message from Runmeter as well but, heh, that just confused me more. With Wi-Fi on or off I still get my run map overlay showing me running right through buildings and cutting corners where I actually turned at right angles on the sidewalk. I have the 4S, as you probably know its got the new GPS chip that gets the Russian satellites (GLONASS) as well as ours. But sometimes I think my 3GS actually performed better while moving and the 4S is better stationary. I know it get a lock really fast.

Meg, I'd like to know if you get the same problems on Runmeter if you do have the 4S.

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Answer 4

sorcc Author

Level 1

9 points

Mar 20, 2012 10:55 AM in response to paulcb

To paulcb -

I don't care if it's a few meters off when stationary. Well, then again maybe I do, centimeters I can handle. I know the vast majority could care less about the GPS being crazy accurate. And some worry about the privacy issues. I am one who really digs GPS technology and I'd simply like to get the best accuracy possible.

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Answer 5

Mar 20, 2012 11:04 AM in response to sorcc

I do not pretend to understand most of this - https://www.e-education.psu.edu/natureofgeoinfo/c5_p19.html

but it seems one of the most comprehensive discussions of GPS accuracy limitations available openly on the web.

To be honest, I see almost no discerble difference in accuracy with wifi on or off (at least not when outside, under open unobstructed sky), which to my limited understanding makes sense since the primary use of wifi is to aid in the time it takes to get a stable fix, not in terms of the accuracy of that fix.

I'd think accuracy is primarily limited by the device itself - that is, limitations in the GPS chipset and clock of the iPhone itself.

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Answer 6

Mar 20, 2012 11:10 AM in response to sorcc

I have a 4S and had a 4 prior to that. I am currently trying to find a running app that has what I consider to be accurate GPS. Like you, I have my obsessive moments. I have used a Garmin GPS watch for years (various models, current is the 405x). However, I decided to use Runmeter because I like the audio feedback and then they added intervals. However, it's routinely WAY off from the Garmin. It thinks I run far faster than I do. The pace difference is 2-3 min/mile faster, distance off by about .5 miles by the time I'm done a 3 mile run. I get slightly better accuracy if I make sure to quit the app and relaunch it. I'm still not happy though. I've tried putting in a pocket, putting it in a belt pouch, putting in in an armband. No difference. Results with JogLog are worse (and the app isn't as nice).

Should you find an accurate running app, do let me know!

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Answer 7

sorcc Author

Level 1

9 points

Mar 20, 2012 1:35 PM in response to IdrisSeabright

I'm not seeing how to quote here. This is to Meg...

I have tried a slew of them. They all seem to be about the same as far as accuracy. I agree about the voice and intervals being the best with Runmeter. I'll have to look at my purchased apps later to see the ones I've deleted. But right now I use Runmeter for walking my dog. I use Nike + for running. With the iPhone you don't need the shoe sensor and all that, just the app. I like that when you look at your "breadcrumb trail" map overlay your changes in speed are color coded. The app is relatively inexpensive, think its $1.99 (US).

I will come back here and post tomorrow if I see any deleted ones that might of been updated or I think might be worth a looky-loo. But as I said, I think the accuracy is dependent on the iPhone, not the apps. But I could be wrong there of course.

And one more thing, the 4S does recieve from the US GPS and Russian GLONASS. I've read it was the first smartphone with the chip to recieve from both systems. The Russians are still adding satellites to their system. As they add more our 4S's (and the 5 and so on) should become more accurate.

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Answer 8

sorcc Author

Level 1

9 points

Mar 20, 2012 1:38 PM in response to Michael Black

To Michael Black-

Thanks for the info and the link, it's in my reading list.

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Answer 9

Mar 20, 2012 6:05 PM in response to sorcc

You quote by clicking the little thought bubble with the quotations marks on it that appears in the tool bar for the reply box (unless you're using Safari on an iOS device). You have already mastered what for many is the tricky maneuver of replying to the correct person! 😉

I have the Nike+ GPS app as well. Used it the other day. I like that it integrates with Path. However, the accuracy wasn't much better and the voice prompts were not nearly as good as Runmeter. I will probably stick with Runmeter for interval alerts and my Garmin watch for my "real" training data.

Thanks and happy trails!

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Answer 10

Mar 28, 2012 6:47 PM in response to sorcc

I tried MapMyRun today. So far, it's been the most accurate (i.e. closest to my Garmin) of any of them.

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Answer 11

sorcc Author

Level 1

9 points

Mar 31, 2012 12:19 PM in response to IdrisSeabright

Thanks, Meg, for the tip. I like it. Can't really say it's more accurate but I like the feature where you can share routes via the website by uploading the data right from the app. Its focus is where mine is, mapping my runs/walks.

But I have the feeling that the gps mapping accuracy is dependant on the iPhone, not the apps. Like, no matter how good the app is it can only be as good as the phones gps chip will let it be. I'm going to try to learn more about all this though.

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