@A and C: I have to comment ;-). I used Skydemon with internal and external GPS sources for quite some time now. In the beginning (up to iOS6) I had almost no GPS dropouts whatsoever, independent of external or internal GPS. Starting with iOS7 and much more prominent in iOS8, there are a lot more dropouts in the Skydemon tracks, BUT this is not related to the GPS source - as neither BadElf nor Garmin GLO nor GNS2000 nor connection to certified GPS via AIRconnect show a different result. These outages appear to occur from the way multitasking was implemented in iOS and they are in other navigational apps like ANP as well. With an app disabling the multitasking there are no dropouts, still.