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Something that's been poking my interest for a while now and I thought I ask the experts here :)
Every time I setup a notification to remind me of something when I arrive somewhere, I get a note from ios5 that enabling wifi will result in a better location recognition than 3G , and since I have a 6GB Data plan, I really don't want to use wifi! Now the question is; shouldn't 3G be more acurate in location recognition? What are your thoughts?
 

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Its because your phone doesn't just use 3G, wifi, or GPS for location services, it actually uses a combination of all three. Having wifi turned off will just disable access to skyhook, making your location services slightly less accurate. You can read more about location services here...

iOS 5: Understanding Location Services
 

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Also depending on where you are wifi alone will typically be much more accurate than 3G or gps. Gps doesn't work well if you don't have a clear line of sight to at least 3 satillites so in dense urban areas where buildings often block a clear line of sight to the sky wifi can be much more accurate as there are frequently many more than 3 wifi networks to triangulate from in urban areas. 3G alone is the least accurate of the bunch.
 

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It's less about the fact that Wi-Fi will make your GPS results more accurate, and more that Wi-Fi will assist your GPS and 3G location finding to find your location faster. I think the prompt is helpful, but I wish Apple would simply disable it after I dismiss it the first time.
 

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dup post
 

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I'm still confused... How does it help being on if you aren't logged into to a wifi server?
Because it doesn't use the specific wifi network you are on, but rather the combination of the wifi networks that are visible in the vicinity of your device.

Bottom line with any form of location triangulation is the more points you have to triangulate from the faster and more accurate a fix yon can get. By using wifi signals in addition to cell tower, and gps satellite (and as of the iPhone 4s the Russian version as well), your device will be able to figure out where it is faster and more accurately.

From my own experience cell tower alone is generally only accurate to +/- 1-2km, add in a partial gps lock (only 1 or 2 satellites) generally improves it to around +/- 500m, full gps signals and/or wifi signals can better that down to a few meters.
 
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