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I am looking to develop a simple application where I just need things like lat/long coordinates probably using the CoreLocation framework. I am leaning towards developing on either the ipad mini or iPad w/ retina.

The tablet will be taken off seas in a boat where there will be no wifi. This rules out the wifi models. My question is, can I buy a 3g/lte model and just use the GPS/Glonas to get coordinates, or will I need to buy an external gps such as the Garmin Glo?

Is this possible without having to pay for the service as well? Is there any recommendation into which carrier to get, (verizon, at@t, or Sprint)? I'm thinking this shouldn't matter because the gps does not use data but rather the built in chip. Lastly, will a 16gb model suffice for just location variables in an app, or should I buy a larger capacity?

Also, can the gps be used with airplane mode disabled?

Cœur
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user2402616
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    Could you tell the non-Russians among us what the heck is "Glonas"? – Sergey Kalinichenko Jul 31 '13 at 13:55
  • Haha I don't know too much about it, just that it is an alternative to GPS. I don't think this will be too much of an issue as I'll probably just use the GPS system. – user2402616 Jul 31 '13 at 14:28
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    It's spelled GLONASS. It's a space based system of 24 satellites similar to GPS. Wikipedia has a nice article on it. – progrmr Aug 01 '13 at 15:16

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If the iPad has built in a GPS device, then of course you can use that.
It does not need wifi or GSM cell to use GPS or GLONASS.
wifi or GSM cell may only speed up the time to first valid fix, by some seconds, which for boats has litte advantage. (for obstructed environmentg like in cities it's an advantage, to have AGPS via GSM for faster init time)

However on boat you will not find much differnece to GPS only like iphone4 compared to GPS + GLOANNS like on iphone4s.
At sea you have open sky and GPS only is fine for everything.

The other things are water proofness, battery consumption, etc.

AlexWien
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  • Pretty much answered everything I was looking for. Except can you explain what you meant by, "However on boat you will not find much differnece to GPS only like iphone4 compared to GPS + GLOANNS like on iphone4s" An upvote will surely follow – user2402616 Jul 31 '13 at 16:56
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    GPS only is sufficient, you dont need GLOANSS. Except in urban canyons where the view to sky is limited, the addional GLONASS satellites is helpfull. ON boat the view to sky is superb, no obstructions from buildings. So it will not make much difference in positional accuracy if you have a GPS only chip (iphone4), or a GPS / GLONASS combined chip (iphone4S+). – AlexWien Jul 31 '13 at 18:17
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    Without GLONASS you may get only 10 meter accuracy, with both usually about 5 meter accuracy. Good enough for boating either way. – progrmr Aug 01 '13 at 15:20
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    @progrmr Whitougt GLOANSS you get 2- 3m, do not interchange GLONASS with EGNOS: EGNOS is the correction grid, to correct ionospeheric delays, which improve GPS from 6-10m to 3-6m, and which is supported by all ios GPS chips – AlexWien Aug 01 '13 at 15:35
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    The horizontalAccuracy value from Core Location currently only returns 5.000 or 10.0000 or higher, nothing in between. Real accuracy may be 3-6 but CL reports 5. – progrmr Aug 01 '13 at 19:28
  • yes, acc is rounded in steps of 5, reason is that acc is vaguely estimated. it would not make sense, to report an accuracy estimation finer than the precision of the estimation. – AlexWien Aug 02 '13 at 09:45
  • Here we have WAAS instead of EGNOS, but I've never seen anything that indicates that iOS GPS chips support either of these correction systems. – progrmr Aug 02 '13 at 20:59
  • @progrmr All recent chips build in the last 5 years support WAAS/EGNOS, so ios, too. find out which GPS chip (broadcom) then you know its supports WAAS/EGNOS. from the accuracy of the chip i see that it uses WAAS / EGNOS. – AlexWien Aug 02 '13 at 21:48