By the way, I tested this unit(XGPS150A), works fine. I disconnected the external GPS while in air. The iPadwas not able to get GPS signals with the internal antenna, within 2-3 minutes,so I connected it back on and was right back on my position.

One thing to note was that SD reported about30-40 feet higher altitude then my Garmin. Don't know why or which is correct(if any of them are, who knows?)

That's correct. SkyDemon asks iOS for the position information - it doesn't (in fact can't) talk directly to the GPS.

Thank you very much. I did not know. That mean that if Skydemon support en external GPS or not does not matter because this is a function in IOS?

The external GPS always overrides the internal one. There is no way of specifically telling which is in use other than checking that the indicator lights are correct on your external device.

I have a iPad 2 (3G version, built-in GPS) that I have connected to a Dual XGPS150 via Bluetooth. How do I configure Skydemon to use that GPS rather then the built in? How do I know witch GPS is in use?

Thank you for sharing your knowledge.