I have a wifi 16GB iPad and an iPhone 4 and Macbook Pro.

Sort of kicking myself for not getting the 3G iPad as I want to use it for marine navigation. Can anyone tell me what the range of the 3G GPS chip is and its area of operation? I know it will work without a phone connection from following other posts, but how far from shore will it work? Will it work in US/Caribbean and Europe for instance? Can't find this info in user guide.

Many thanks

GPS is a satellite based system that will work almost everywhere on the globe. It does have some limitations on accuracy in the polar regions.

There are add on units for wifi iPads that will give you gps.

I think he means the sensitivity. I believe, from using it, it is +/- 3 meters. All dependent on signal strength (not 3G signal) and overhead coverage. It is as good as any consumer-grade car GPS units.

Originally Posted by deckyon

It is as good as any consumer-grade car GPS units.

Yep.. I use my iPad now in place of my dedicated Magellan GPS unit.. It's just as accurate and I like the 9 inch screen

FWIW, there is what appears to be a pretty good marine navigation app in the app store.. I've never tried it, but there is info about it here --> iNavX™ - Marine Navigation App for iPhone and iPad

Yeah the gps is decent on the wifi version but with the dedicated gps chip in the 3G models gets near perfect readings.

Why would he mean "sensitivity" when he specifically states "how far from shore will it work?" Between that and "area of operation" I think rkelac is right in trying to explain how GPS actually works.
Maybe the "assisted" part of A-GPS confused him. Since that is the only terrestrial thing the 3G iPad would care about in terms of GPS location.

If something has a full GPS chipset and radio, it will work anywhere on the globe you can see the sky. Atmospheric conditions can interfere with GPS and is more noticeable with GPS than nearly any other electronic device. And it generally safe to assume that when talking about GPS that it will work anywhere on the globe. Global Positioning System. A GPS has no "range", hence the Global in the name.

With the wifi only model, there is no actual GPS chipset. It depends on the wifi router knowing where it is by checking the IP against a database way off in the background. Therefore, you have to be within range of the wifi for this to work. You could lose that connection within feet of the shore.

A-GPS is nothing more than a marketing term latching onto a recognizable technology that is the GPS.

Do not try and navigate on a boat without a full-fledged GPS - iPad 3G or dedicated GPS unit.

Originally Posted by AML

Sort of kicking myself for not getting the 3G iPad as I want to use it for marine navigation.

There may be a way out, see G-Fi - World's First Mobile Network / GPS Router - Now Featuring Navmii Navigation Suite - Home. They claim "military precision" but that probably won't make a significant difference for most consumer uses.

You would need to check that it works with the iPad but it sounds like it should. The important thing is that it feeds data into the iPad's Location Services.

The next challenge would be find a navigation App that carries maps onboard. I am sure that you know that the Maps App downloads maps, via the internet, on the fly. I think there are some around already and sone on the way.

I too am frustrated the the WiFi only iPad doesn't have the GPS chipset onboard. A plus for this device is that the GPS receiver can be located for better reception.

Originally Posted by rkelac

GPS is a satellite based system that will work almost everywhere on the globe. It does have some limitations on accuracy in the polar regions...

Darn it! There goes your plans for that Antarctica vacay!!! lol

Thanks for all your help. Yes I am aware that GPS is a global system and I have two GPS antennae on my boat, but it seems almost unbelievable that a small chip in the 3G iPad can give as good reception as a dedicated GPS antenna. I have also looked at small add on GPS antennae for iPad and am thinking about putting iPad into a waterproof bag (Aquapac do a reasonable one and I hvae a smaller one for my iPhone).

I think I will be able to get an NMEA repeat from my wireless transmitter via my old PC which runs a windows based nav programme I don't like very much. The NMEA should work with iNavX, if not I may scrap the PC and put a Macmini on board to run the MacENC software.

I already have the Navionics programme which works fine on my iPhone 4 at sea with its GPS chip, but haven't yet tried it with iPad. The charts on that programme are all stored on the iPad/iPhone. Yes, I am aware that other maps like google are downloaded as required and so require an active internet connection to work.

I will also have a look at G-Fi

Many thanks for all your helpful input