mutability / dump1090

Dump1090 is a simple Mode S decoder for RTLSDR devices
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DF18 message gets a '~' prefix #228

Closed marcus-aa closed 6 years ago

marcus-aa commented 6 years ago

LFMN Airport has a reference transmitter that sends out DF18:2 and DF18:8 messages. It's ICAO code gets a tilde prefix which causes problem when reading the JSON file.

Is this intended? I know '~' prefix is used for anonymized FA mlat targets, but this is not the case here.

´´´ 2018-03-26 01:30:07.840 DEBUG 91390DFF40000E77E4B8A707FDC2; 2018-03-26 01:30:07.840 DEBUG DF18 Type 8 ICAO: 390DFF CF 1 NIC 0 GR 1 TS 1 CPR 1 TIMESTAMP 1522020607 2018-03-26 01:30:12.670 DEBUG 91390DFF40000E77E4B8A707FDC2; 2018-03-26 01:30:12.670 DEBUG DF18 Type 8 ICAO: 390DFF CF 1 NIC 0 GR 1 TS 1 CPR 1 TIMESTAMP 1522020612 2018-03-26 01:30:16.749 DEBUG 91390DFF124851A0820820348689; 2018-03-26 01:30:16.750 DEBUG DF18 Type 2 ICAO: 390DFF CALLSIGN REF CAT 2 CAT2 2 CF 1 TIMESTAMP 1522020616 2018-03-26 01:30:17.620 DEBUG 91390DFF4000086890E19F07179C; 2018-03-26 01:30:17.620 DEBUG DF18 Type 8 ICAO: 390DFF CF 1 NIC 0 GR 1 TS 1 CPR 0 TIMESTAMP 1522020617 2018-03-26 01:30:22.540 DEBUG *91390DFF40000E77E4B8A707FDC2; 2018-03-26 01:30:22.540 DEBUG DF18 Type 8 ICAO: 390DFF CF 1 LAT 43.6532 LON 7.20139 NIC 0 GR 1 TS 1 CPR 1 TIMESTAMP 1522020622 ´´´

mutability commented 6 years ago

Yes, that looks correct. Generally the ~ prefix means "not using the ICAO addressing scheme", in this case because DF=18 CF=1 means "reserved for ADS-B Message in which the AA field holds anonymous address or ground vehicle address or fixed obstruction address"

*91390dff40000e77e4b8a707fdc2;
CRC: 000000
DF:18 AA:390DFF CF:1 ME:40000E77E4B8A7
 Extended Squitter (Non-Transponder) Surface position (8)
  Other Address: 390DFF (ADS-B, other addressing scheme)
  Air/Ground:    ground
  CPR type:      Surface
  CPR odd flag:  odd
  CPR latitude:  (80882)
  CPR longitude: (47271)
  CPR decoding:  none