I've just installed my new bad GPS fix detection algorithm. It should detect bad fixes about as well as before, but produce less false positives. The new algorithm looks at the previously received packets instead of the previously accepted packets, and is also slightly adaptive, taking into account more history than just the previous single accepted position.
It should work better for jets (traveling close to 1000 km/h), although during the takeoff acceleration some points might be dropped. After some initial test flights we'll be fixing that. :)
It should also better handle the case where the initial transmission happens to be somewhere far off. It seems like there are a bunch of stations which always wake up in Tokyo and then start transmitting their correct position in the US or Europe. Probably the GPS manufacturer has decided to show it's office location instead of the standard 0/0 lat/lon, and either does not indicate the bad fix in the NMEA sentence, or the tracker ignores that bit of information and transmits the bad position. These should now jump to the correct position after just a couple of packets.
The algorithm also ignores positions which were sent more than 2 hours ago, so if you take an intercontinental flight and start transmitting your new position immediately, it should just work!
Feedback is more than welcome!