Does the app need a "GPS library"? It should merely need to call the IOS API. But maybe for a bluetooth GPS it can communicate with it directly. The Dual GPS app which shows the satellite constellation is obviously not talking to it via the API because that info is blocked by Apple.

On the plus side, the Dual GPS is doing a good battery life - I am at 15hrs now and it is showing 30% left.

I think the ANP talks directly to the GPS along with being able to share the GPS data by Bluetooth. I can choose between my Bluetooth GPS and internal from within the app.

In answer to your question about maps, no you can't use your own, you buy through the store. Which is simpler for my needs. It does include loads of free maps as well though.

As per my previous post, my understanding is if an app uses the iOS API, it has no way of telling which GPS device, if any, is connected. It also has no way of knowing whether the device has a signal (other than by looking at the horizontal accuracy and time of the most recent "fix"). The API could be reporting a cellular triangulation fix, accurate to maybe a mile, it could be reporting using the internal GPS or it could be reporting using an external GPS. It hides all of this from the developer. Its designed for one off location queries from shopping apps - not navigation.
To get more detailed, and controllable information (such as being able to select a GPS device), a developer has to use code libraries from else where or write the code himself to communicate to the GPS (internal or external) devices.

OK; I see that. But it's not hard because every normal GPS does bluetooth and NMEA is standard. That is how the "GPS world" worked before Jobs did it his own way....... and compatibility was IME excellent across products.

What I don't know is whether it will ever be possible to use any normal bluetooth / NMEA GPS with the Ipad, because under Settings none of them show up at all. Jobs seems to have banned the support of a normal "serial" bluetooth device. But evidently units like the Dual do somehow deliver a full-featured data stream over bluetooth, into which they can stick any data they want, and presumably this could be straight NMEA again (anything else would be totally illogical in marketing terms).

I do hope that Oziexplorer does this correctly and not just uses the stupid IOS GPS API...

Ipad in flight
 

With all do respect
My dear feiend i found ipad realy useful and oprational in flight i have checked its accuracy with nav sys of aircraft ( fokker 100) several time and its realy reliable the only thing needs to mention is that avoid using it contineously since desply on cause ipad warm up and heat up which cause to battry loss ...
Using it in short intervall is a good remedy and avoid direct sun light but overally its a problem you have not to deal with in night flight .
Wish you all safe and sound flights .:)

Can confirm I have had far more reliable GPS from my iPad both in the DA-40 and as SLF on BA or easy than I ever got from my Pilot III or Garmin 196.

Bought an external bluetooth GPS but have never used it in anger.

As an update on Bluetooth GPS', the Bad Elf GPS Pro drives six units with a 16 hour battery life. You can get one on amazon.com for about $100US. I've had it on 11 hour flights driving two iPads and an iPhone and the battery charge indicator doesn't move one bar.

Bet the iPad batteries didn't last that long :-).

We have a power source in the airplane to keep the iPads going.

query
 

I have a 32 gb ipad Air.

WIFI only.

Am i correct in saying i would need to purchase one of the plug in GPS's into the bottom of the ipad in order to make eg SKY DEMON to work..?

any info appreciated

You need a cellular iPad for an internal GPS, so yes, you have to buy an external GPS. I have, and recommend, a Bad Elf GPS Pro Bluetooth. They also now make a plug-in GPS for the Lightning connector.

What concerns me is how fragile the Bad Elf Lightning connector appears to be, knock it whilst it's in situ and you have a broken Bad Elf, I'd ALWAYS go for a Bluetooth system (I have the GNS 5870 but rarely use it as the GPS reception of my Tabs / iPad is more than adequate)

I've been using the Garmin GLO GPS/GLONASS product with an iPad Mini and it apparently works just fine. I initially tried with the Airspace Avoid FREE app and NAVFREE the car sat-nav system both work extremely well.