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Definately some aircraft that appear to deliberately conceal their position:G-BUUR with position N12 00.0 E000 00.0G-BTPF with positions N12 00.0 E000 00.0 and S42 00.0 E000 00.0
Quote from: tarbat on January 23, 2009, 09:20:43 AMDefinately some aircraft that appear to deliberately conceal their position:G-BUUR with position N12 00.0 E000 00.0G-BTPF with positions N12 00.0 E000 00.0 and S42 00.0 E000 00.0I find that hard to believe. I've logged G-BUUR and G-BTPF many times since, respectively, Oct 2006 and Nov 2007, and both as recently as this week. Neither has ADS-B so I have no idea where those spurious coordinates originated from but they certainly didn't come from the aircraft !
I don't believe there is much, if any, error correction in the MOde S transmissions.It could be simply that a corrupted message is received that happens to appear to contain this information.
Quote from: Fenris on January 23, 2009, 03:14:15 PMI don't believe there is much, if any, error correction in the MOde S transmissions.It could be simply that a corrupted message is received that happens to appear to contain this information.The Mode S spec includes a 24-bit parity string in the ACAS and ADS-B squitters, which ought to be usable by Mode S receivers, although I have no idea whether RadarBox or SBS actually make use of this.The surveillance interrogation responses, OTOH, overlay the parity on top of the aircraft address, which means that even one mangled bit in a 56- or 112-byte packet can produce invalid data with no way that we can detect this.