John Miller wrote:
HOOK:
He has no ADSB. This tablet worked for 3 years. I did have this issue very infrequently on my LG Gpad, but again it was while approaching Palmdale Skunks Works. As I mentioned to Brian in my most recent reply to him one consideration was that these failures have occurred within 5 miles of March AFB. I am wondering about purposeful GPS interference as like what is happening in the Southeast.
John M
Thanks to your logs, I've narrowed down the root cause, which looks like it could be an iFly GPS defect. But I do not yet have a solution for this bug, nor have I determined the exact original of this fault.
The reason the failure is dependent upon geographic location is that for some odd reason, on that device it's mis-parsing the following value for Longitude:
$GPRMC,192459.7,A,3343.874103,N,-118-1.028828,W,1.3,190.4,150219,12.6,E,A*18
The "-118-1.028828,W" should be parsed as "118.01714680989583 West", but for some unknown reason on that device, it's parsing it as: "11.35046 W"!! And therefore, it recognizes this as "bad data" (it's not over North-America) and so reverts back to showing the default location - which is often your Flight Plan start location.
I can't figure out how parsing is arriving at this erroneous value. The way the RMC spec is made, it works like this:
Result = (118 degrees + 1.028828 Minutes) == 118.017147 degrees.
If any math whiz out there can surmise how a device can incorrectly parse this, please speak up.
So my default guess here is that the other device has different "cultural settings" which does influence how #'s are parse from text (e.g. commas and periods are switched).
For some odd reason, though, once you cross below 118 deg West (go east) so that it becomes 117.999 W.... then it starts working.
This *could* be a defect on that device's firmware, which then would make this NOT an iFly GPS defect.
First things to try:
1. Check the Device Regional/Culture settings -- make sure it's USA/English.
2. Check for firmware upgrades from the device manufacturer.
Otherwise... I'm currently out of other guesses.