As I mentioned on the other forum, I wonder if it’s something to do with the frequency of your home field and your radio putting out something on that frequency.
Perhaps sometime when you are well away from the field, and not talking to anyway, you could tune in that frequency and make a short transmission and see if the problem reoccurs at that point?
that’s something I will try @dublinpilot thanks. I’m also wondering if it could be something the panel mounted GNS430 is doing to interfere somehow?
Interference is also possible.
I have an ipad 2 whose GPS is rubbish in the TB20. Also check for 11th and 13th sub harmonics of 1575MHz being used on VHF.
Peter wrote:
Also check for 11th and 13th sub harmonics of 1575MHz being used on VHF.
According to Garmin’s GTN Xi series IM, the following COM channels are critical:
121.150, 121.175, 121.185, 121.190, 121.200, 121.225, 121.250, 131.200,
131.225, 131.250, 131.275, 130.285, 131.290, 131.300, 131.325, 131.350
After installation of an GTN Xi device (and, I would guess, any GPS device), a 35 second transmission should be made on each frequency using each COM radio. During that transmission the loss of integrity flag (LOI) should not appear on the GPS box.
See here for some very real VHF interference. The KLN94 (and to a lesser extent some portables) got totally wiped out by the KX155A transmitting on the frequencies described in the link. Cause? Not such a clean signal transmitted by the KX155A, plus crap quality coax used by Socata (and used by most avionics installers, even today, but much more universally in years past – I have been free issuing RG400 which they reluctantly use).
If you go to whatever page is showing the space vehicle signal levels then you can quickly see these diving downwards when you transmit. Every IFR GPS has a page showing this, and Android apps can show it; not sure if this is possible with an Ipad. IIRC – did some work on this years ago, around here – the “Apple special” GPS API did not return this data and just gave you a general “accuracy value for the nearest McDonalds”. It was only NMEA data which gave the individual space vehicle signal data.
In case the OP wonders why the image in post #1 has shrunk, it is because images > 600 pixels wide prevent the thread being promoted to the home page, so I fix up the 1st post of any interesting thread 
Just thought I’d update this thread following a few flights I did yesterday. I paired a Garmin Glo 2 device my iPad and can happily report rock solid GPS performance with none of the erratic GPS traces that I’d posted previously.
I can only assume that something has changed in the way iOS uses / derives location when using built in sources.
Here is a SkyDemon log from my departure from Elstree:
Glad you managed to smooth our your hand flying ;-)
Haha :-)
Also just to add, I was meaning to put the iPad into airplane mode and just leave Bluetooth on so as to ensure location data was only being fed from the Glo device but I’d forgotten to do that.
Therefore it would seem with the Glo attached it seems to ‘win’ against the anomalous sources.
