i Pad and gps

[gregship]

As the original poster i am still very confused ,OP are basically saying yes or no you have to have 3g. what if i didnt have 3g ,wifi and no mobile signal and inthe middle of the shipping lanes ,is it only the ipad3 has the proper gps built in as one poster has suggested

 

[vyv_cox]

Very inaccurate. No wifi, 3G or any other signal required. It has in built full function GPS. Some will say it doesn't and that means that they don't have a 3g iPad or they would know better.

If you read my earlier posts you will see that what you write is not strictly true, at least of my iPad 2. With 3G switched off but wifi enabled I have waited for hours for gps to find me. With it switched on, in some places gps locates me immediately but in other places, maybe where the 3G signal is a long way away, the gps places me in sometimes ridiculous places, e.g. up a mountain.

 

[Rivers & creeks]

If you read my earlier posts you will see that what you write is not strictly true, at least of my iPad 2. With 3G switched off but wifi enabled I have waited for hours for gps to find me. With it switched on, in some places gps locates me immediately but in other places, maybe where the 3G signal is a long way away, the gps places me in sometimes ridiculous places, e.g. up a mountain.

None of the four iPads in our family have that problem and it sounds like your GPS chip may be faulty. Three of the iPad's have never even had cellular enabled and find themselves almost instantly. They are an iPad 1, mini, 3 and Air so the fault you're experiencing isn't due to it being an early iPad. We navigate with the wifi, Bluetooth and cellular data switched off to preserve battery and the positioning is rock solid, corresponding exactly with the old Raymarine plotter we use to control the autopilot.

 

[mrming]

As the original poster i am still very confused ,OP are basically saying yes or no you have to have 3g. what if i didnt have 3g ,wifi and no mobile signal and inthe middle of the shipping lanes ,is it only the ipad3 has the proper gps built in as one poster has suggested

1) All the 3G iPad models have proper GPS.

2) You do not need any kind of data signal (wifi or 3G) for the GPS to function.

3) Wifi only iPads do not have GPS.

These are the facts. As Lazy Kipper says, it sounds like vyv_cox's iPad has a technical fault.

 

[Buck Turgidson]

If you read my earlier posts you will see that what you write is not strictly true, at least of my iPad 2. With 3G switched off but wifi enabled I have waited for hours for gps to find me. With it switched on, in some places gps locates me immediately but in other places, maybe where the 3G signal is a long way away, the gps places me in sometimes ridiculous places, e.g. up a mountain.

Ok I think we need to be very clear about something.
The location service on your iPad will work a) without GPS and wifi. b) without cell and wifi and c) without GPS and cell.

It's really important to understand this when thinking about position accuracy. So when you are just connected to wifi the location service knows where the server is and therefore you are "close" to that. When only connected to cell the the position can be quite accurate but is not GPS derived and can be quite wrong sometimes. IF you have GPS position and are not in the bottom of a canyon or downtown in a high rise city the position will be accurate to <13m and 95% of the time better than the length of your boat.

The problem is knowing which location service is actually being used. As I said earlier Apple don't release the code for developers to do this but you can see update rates on apps such as GPS Data (free and I have no connection). Using this app you can, by switching off cell then wifi detect if you actually have a GPS position or not. You will also see that the ipad uses inertial data to coast even when it doesn't have a position update. So the position changes and you may be deceived into thinking this is fixing from outside data when it isn't. What will happen in this case is the position will drift with time and the error will grow. You can see this on the GPS Data app as position accuracy is displayed and time of last fix is also displayed.

GPS is a position sensor used by the iPad to derive it's position, it also uses Cell data and it also uses wifi data and will use whichever is available to it. The user however has no indication of which data is being used and it's only by a process of elimination that you can find out.

so your "GPS places me in sometimes ridiculous places " statement is not correct. What it should say is "My iPad location service places me in sometimes ridiculous places" and this probably means your iPad has a fault either with the chip (Broadcom BCM4751) or the antenna.

There are several posters on this thread who have used their iPads in oceans with no chance of wifi or cell data (including myself) and have perfectly good GPS data.

Last note, is that the latest com chip being used in iphones and ipad is the Qualcomm WTR1605L that not only includes GPS but also Glonass and Beidou. Three GNSS constellations in one comm chip.

 

[Vegable]

Being a thick blacksmith, I'm a bit lost now!
I can understand how the tablet locates using gps and using wifi, but how does it work when out at sea using its location "software". What does it use as it's reference data? Dead reckoning?
A very interesting topic.
Mike

 

[mjcoon]

... So when you are just connected to wifi the location service knows where the server is and therefore you are "close" to that. ...

How does the "location service" know where the "server" is? I ask specifically because in May I spent a fortnight on a charter yacht that had its own WiFi hot spot that of course travelled around with us. So far as I know our various devices used their genuine GPS to get positions, possibly with assistance from downloaded almanacs (which is not part of the localisation process).

But I do not know how the yacht's hot spot achieved connection to the internet. Any charges for that were included in the charter fee, so ignorance is/was bliss! Nor whether any location service could be supported by that indirect route.

Mike.

 

[Buck Turgidson]

How does the "location service" know where the "server" is? I ask specifically because in May I spent a fortnight on a charter yacht that had its own WiFi hot spot that of course travelled around with us. So far as I know our various devices used their genuine GPS to get positions, possibly with assistance from downloaded almanacs (which is not part of the localisation process).

But I do not know how the yacht's hot spot achieved connection to the internet. Any charges for that were included in the charter fee, so ignorance is/was bliss! Nor whether any location service could be supported by that indirect route.

Mike.

Without knowing the installation it's impossible to know.

For everyone else here is the apple explanation of location services:
http://support.apple.com/kb/HT5594

 

[Rivers & creeks]

I just don't get how difficult it is to understand that it has a GPS like your phone, TomTom, in car sat nav etc etc etc. iPads with a cellular data chip have a real, full proper and dead good GPS, just like your boat plotter does. There are some extras it has as well but it has normal boring ordinary GPS.

 

[NUTMEG]

I just don't get how difficult it is to understand that it has a GPS like your phone, TomTom, in car sat nav etc etc etc. iPads with a cellular data chip have a real, full proper and dead good GPS, just like your boat plotter does. There are some extras it has as well but it has normal boring ordinary GPS.

Can not get much clearer than that! Bet another thread on this pops up in a couple of months though

 

[Stemar]

If buying primarily for the use of the Navionics app - would a tablet like this Lenovo do the job ?
http://shop.lenovo.com/gb/en/tablets/lenovo/s-series/s5000/#tab-tech_specs
It is wifi only but it does have gps . The purchase cost is considerably less than an ipad mini with gps. Any good ?

Have a look at Londonchartplotters. You could pay a lot less and have a plotter app & UK charts installed as well. They're currently out of stock of the 7.8" tablet I want, but I've got one on back order for delivery in a few days. They also double as (rather oversized) phones as well.