The wikipedia page has some info, looks like various CRC and parity checks. Maybe the receiver was just ignoring them, and receiving faulty data. I dunno, it s

The wikipedia page has some info, looks like various CRC and parity checks. Maybe the receiver was just ignoring them, and receiving faulty data. I dunno, it seems to me like that GPS receiver had fairly bad software. If you get packets from a bunch of different satellites but one is way off, it seems like good sense to throw that one away.