// Part of dump1090, a Mode S message decoder for RTLSDR devices. // // mode_s.c: Mode S message decoding. // // Copyright (c) 2014-2016 Oliver Jowett // // This file is free software: you may copy, redistribute and/or modify it // under the terms of the GNU General Public License as published by the // Free Software Foundation, either version 2 of the License, or (at your // option) any later version. // // This file is distributed in the hope that it will be useful, but // WITHOUT ANY WARRANTY; without even the implied warranty of // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU // General Public License for more details. // // You should have received a copy of the GNU General Public License // along with this program. If not, see . // This file incorporates work covered by the following copyright and // permission notice: // // Copyright (C) 2012 by Salvatore Sanfilippo // // All rights reserved. // // Redistribution and use in source and binary forms, with or without // modification, are permitted provided that the following conditions are // met: // // * Redistributions of source code must retain the above copyright // notice, this list of conditions and the following disclaimer. // // * Redistributions in binary form must reproduce the above copyright // notice, this list of conditions and the following disclaimer in the // documentation and/or other materials provided with the distribution. // // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT // HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. #include "dump1090.h" #include "ais_charset.h" /* for PRIX64 */ #include // // ===================== Mode S detection and decoding =================== // // // /* A timestamp that indicates the data is synthetic, created from a * multilateration result */ #define MAGIC_MLAT_TIMESTAMP 0xFF004D4C4154ULL //========================================================================= // // Given the Downlink Format (DF) of the message, return the message length in bits. // // All known DF's 16 or greater are long. All known DF's 15 or less are short. // There are lots of unused codes in both category, so we can assume ICAO will stick to // these rules, meaning that the most significant bit of the DF indicates the length. // int modesMessageLenByType(int type) { return (type & 0x10) ? MODES_LONG_MSG_BITS : MODES_SHORT_MSG_BITS ; } // //========================================================================= // // In the squawk (identity) field bits are interleaved as follows in // (message bit 20 to bit 32): // // C1-A1-C2-A2-C4-A4-ZERO-B1-D1-B2-D2-B4-D4 // // So every group of three bits A, B, C, D represent an integer from 0 to 7. // // The actual meaning is just 4 octal numbers, but we convert it into a hex // number tha happens to represent the four octal numbers. // // For more info: http://en.wikipedia.org/wiki/Gillham_code // static int decodeID13Field(int ID13Field) { int hexGillham = 0; if (ID13Field & 0x1000) {hexGillham |= 0x0010;} // Bit 12 = C1 if (ID13Field & 0x0800) {hexGillham |= 0x1000;} // Bit 11 = A1 if (ID13Field & 0x0400) {hexGillham |= 0x0020;} // Bit 10 = C2 if (ID13Field & 0x0200) {hexGillham |= 0x2000;} // Bit 9 = A2 if (ID13Field & 0x0100) {hexGillham |= 0x0040;} // Bit 8 = C4 if (ID13Field & 0x0080) {hexGillham |= 0x4000;} // Bit 7 = A4 //if (ID13Field & 0x0040) {hexGillham |= 0x0800;} // Bit 6 = X or M if (ID13Field & 0x0020) {hexGillham |= 0x0100;} // Bit 5 = B1 if (ID13Field & 0x0010) {hexGillham |= 0x0001;} // Bit 4 = D1 or Q if (ID13Field & 0x0008) {hexGillham |= 0x0200;} // Bit 3 = B2 if (ID13Field & 0x0004) {hexGillham |= 0x0002;} // Bit 2 = D2 if (ID13Field & 0x0002) {hexGillham |= 0x0400;} // Bit 1 = B4 if (ID13Field & 0x0001) {hexGillham |= 0x0004;} // Bit 0 = D4 return (hexGillham); } // //========================================================================= // // Decode the 13 bit AC altitude field (in DF 20 and others). // Returns the altitude, and set 'unit' to either UNIT_METERS or UNIT_FEET. // static int decodeAC13Field(int AC13Field, altitude_unit_t *unit) { int m_bit = AC13Field & 0x0040; // set = meters, clear = feet int q_bit = AC13Field & 0x0010; // set = 25 ft encoding, clear = Gillham Mode C encoding if (!m_bit) { *unit = UNIT_FEET; if (q_bit) { // N is the 11 bit integer resulting from the removal of bit Q and M int n = ((AC13Field & 0x1F80) >> 2) | ((AC13Field & 0x0020) >> 1) | (AC13Field & 0x000F); // The final altitude is resulting number multiplied by 25, minus 1000. return ((n * 25) - 1000); } else { // N is an 11 bit Gillham coded altitude int n = modeAToModeC(decodeID13Field(AC13Field)); if (n < -12) { return INVALID_ALTITUDE; } return (100 * n); } } else { *unit = UNIT_METERS; // TODO: Implement altitude when meter unit is selected return INVALID_ALTITUDE; } } // //========================================================================= // // Decode the 12 bit AC altitude field (in DF 17 and others). // static int decodeAC12Field(int AC12Field, altitude_unit_t *unit) { int q_bit = AC12Field & 0x10; // Bit 48 = Q *unit = UNIT_FEET; if (q_bit) { /// N is the 11 bit integer resulting from the removal of bit Q at bit 4 int n = ((AC12Field & 0x0FE0) >> 1) | (AC12Field & 0x000F); // The final altitude is the resulting number multiplied by 25, minus 1000. return ((n * 25) - 1000); } else { // Make N a 13 bit Gillham coded altitude by inserting M=0 at bit 6 int n = ((AC12Field & 0x0FC0) << 1) | (AC12Field & 0x003F); n = modeAToModeC(decodeID13Field(n)); if (n < -12) { return INVALID_ALTITUDE; } return (100 * n); } } // //========================================================================= // // Decode the 7 bit ground movement field PWL exponential style scale (ADS-B v2) // static float decodeMovementFieldV2(unsigned movement) { // Note : movement codes 0,125,126,127 are all invalid, but they are // trapped for before this function is called. // Each movement value is a range of speeds; // we return the midpoint of the range (rounded to the nearest integer) if (movement >= 125) return 0; // invalid else if (movement == 124) return 180; // gs > 175kt, pick a value.. else if (movement >= 109) return 100 + (movement - 109 + 0.5) * 5; // 100 < gs <= 175 in 5kt steps else if (movement >= 94) return 70 + (movement - 94 + 0.5) * 2; // 70 < gs <= 100 in 2kt steps else if (movement >= 39) return 15 + (movement - 39 + 0.5) * 1; // 15 < gs <= 70 in 1kt steps else if (movement >= 13) return 2 + (movement - 13 + 0.5) * 0.50; // 2 < gs <= 15 in 0.5kt steps else if (movement >= 9) return 1 + (movement - 9 + 0.5) * 0.25; // 1 < gs <= 2 in 0.25kt steps else if (movement >= 3) return 0.125 + (movement - 3 + 0.5) * 0.875 / 6; // 0.125 < gs <= 1 in 0.875/6 kt step else if (movement >= 2) return 0.125 / 2; // 0 < gs <= 0.125 // 1: stopped, gs = 0 // 0: no data else return 0; } // //========================================================================= // // Decode the 7 bit ground movement field PWL exponential style scale (ADS-B v0) // static float decodeMovementFieldV0(unsigned movement) { // Note : movement codes 0,125,126,127 are all invalid, but they are // trapped for before this function is called. // Each movement value is a range of speeds; // we return the midpoint of the range if (movement >= 125) return 0; // invalid else if (movement == 124) return 180; // gs >= 175kt, pick a value.. else if (movement >= 109) return 100 + (movement - 109 + 0.5) * 5; // 100 < gs <= 175 in 5kt steps else if (movement >= 94) return 70 + (movement - 94 + 0.5) * 2; // 70 < gs <= 100 in 2kt steps else if (movement >= 39) return 15 + (movement - 39 + 0.5) * 1; // 15 < gs <= 70 in 1kt steps else if (movement >= 13) return 2 + (movement - 13 + 0.5) * 0.50; // 2 < gs <= 15 in 0.5kt steps else if (movement >= 9) return 1 + (movement - 9 + 0.5) * 0.25; // 1 < gs <= 2 in 0.25kt steps else if (movement >= 2) return 0.125 + (movement - 2 + 0.5) * 0.125; // 0.125 < gs <= 1 in 0.125kt step // 1: stopped, gs < 0.125kt // 0: no data else return 0; } // Correct a decoded native-endian Address Announced field // (from bits 8-31) if it is affected by the given error // syndrome. Updates *addr and returns >0 if changed, 0 if // it was unaffected. static int correct_aa_field(uint32_t *addr, struct errorinfo *ei) { int i; int addr_errors = 0; if (!ei) return 0; for (i = 0; i < ei->errors; ++i) { if (ei->bit[i] >= 8 && ei->bit[i] <= 31) { *addr ^= 1 << (31 - ei->bit[i]); ++addr_errors; } } return addr_errors; } // Score how plausible this ModeS message looks. // The more positive, the more reliable the message is // 1000: DF 0/4/5/16/24 with a CRC-derived address matching a known aircraft // 1800: DF17/18 with good CRC and an address matching a known aircraft // 1400: DF17/18 with good CRC and an address not matching a known aircraft // 900: DF17/18 with 1-bit error and an address matching a known aircraft // 700: DF17/18 with 1-bit error and an address not matching a known aircraft // 450: DF17/18 with 2-bit error and an address matching a known aircraft // 350: DF17/18 with 2-bit error and an address not matching a known aircraft // 1600: DF11 with IID==0, good CRC and an address matching a known aircraft // 800: DF11 with IID==0, 1-bit error and an address matching a known aircraft // 750: DF11 with IID==0, good CRC and an address not matching a known aircraft // 375: DF11 with IID==0, 1-bit error and an address not matching a known aircraft // 1000: DF11 with IID!=0, good CRC and an address matching a known aircraft // 500: DF11 with IID!=0, 1-bit error and an address matching a known aircraft // 1000: DF20/21 with a CRC-derived address matching a known aircraft // 500: DF20/21 with a CRC-derived address matching a known aircraft (bottom 16 bits only - overlay control in use) // -1: message might be valid, but we couldn't validate the CRC against a known ICAO // -2: bad message or unrepairable CRC error static unsigned char all_zeros[14] = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 }; int scoreModesMessage(unsigned char *msg, int validbits) { int msgtype, msgbits, crc, iid; uint32_t addr; struct errorinfo *ei; if (validbits < 56) return -2; msgtype = getbits(msg, 1, 5); // Downlink Format msgbits = modesMessageLenByType(msgtype); if (validbits < msgbits) return -2; if (!memcmp(all_zeros, msg, msgbits/8)) return -2; crc = modesChecksum(msg, msgbits); switch (msgtype) { case 0: // short air-air surveillance case 4: // surveillance, altitude reply case 5: // surveillance, altitude reply case 16: // long air-air surveillance case 24: // Comm-D (ELM) case 25: // Comm-D (ELM) case 26: // Comm-D (ELM) case 27: // Comm-D (ELM) case 28: // Comm-D (ELM) case 29: // Comm-D (ELM) case 30: // Comm-D (ELM) case 31: // Comm-D (ELM) return icaoFilterTest(crc) ? 1000 : -1; case 11: // All-call reply iid = crc & 0x7f; crc = crc & 0xffff80; addr = getbits(msg, 9, 32); ei = modesChecksumDiagnose(crc, msgbits); if (!ei) return -2; // can't correct errors // see crc.c comments: we do not attempt to fix // more than single-bit errors, as two-bit // errors are ambiguous in DF11. if (ei->errors > 1) return -2; // can't correct errors // fix any errors in the address field correct_aa_field(&addr, ei); // validate address if (iid == 0) { if (icaoFilterTest(addr)) return 1600 / (ei->errors + 1); else return 750 / (ei->errors + 1); } else { if (icaoFilterTest(addr)) return 1000 / (ei->errors + 1); else return -1; } case 17: // Extended squitter case 18: // Extended squitter/non-transponder ei = modesChecksumDiagnose(crc, msgbits); if (!ei) return -2; // can't correct errors // fix any errors in the address field addr = getbits(msg, 9, 32); correct_aa_field(&addr, ei); if (icaoFilterTest(addr)) return 1800 / (ei->errors+1); else return 1400 / (ei->errors+1); case 20: // Comm-B, altitude reply case 21: // Comm-B, identity reply if (icaoFilterTest(crc)) return 1000; // Address/Parity #if 0 // This doesn't seem useful, as we mistake a lot of CRC errors // for overlay control if (icaoFilterTestFuzzy(crc)) return 500; // Data/Parity #endif return -2; default: // unknown message type return -2; } } // //========================================================================= // // Decode a raw Mode S message demodulated as a stream of bytes by detectModeS(), // and split it into fields populating a modesMessage structure. // static void decodeExtendedSquitter(struct modesMessage *mm); // return 0 if all OK // -1: message might be valid, but we couldn't validate the CRC against a known ICAO // -2: bad message or unrepairable CRC error int decodeModesMessage(struct modesMessage *mm, unsigned char *msg) { // Work on our local copy. memcpy(mm->msg, msg, MODES_LONG_MSG_BYTES); if (Modes.net_verbatim) { // Preserve the original uncorrected copy for later forwarding memcpy(mm->verbatim, msg, MODES_LONG_MSG_BYTES); } msg = mm->msg; // don't accept all-zeros messages if (!memcmp(all_zeros, msg, 7)) return -2; // Get the message type ASAP as other operations depend on this mm->msgtype = getbits(msg, 1, 5); // Downlink Format mm->msgbits = modesMessageLenByType(mm->msgtype); mm->crc = modesChecksum(msg, mm->msgbits); mm->correctedbits = 0; mm->addr = 0; // Do checksum work and set fields that depend on the CRC switch (mm->msgtype) { case 0: // short air-air surveillance case 4: // surveillance, altitude reply case 5: // surveillance, altitude reply case 16: // long air-air surveillance case 24: // Comm-D (ELM) case 25: // Comm-D (ELM) case 26: // Comm-D (ELM) case 27: // Comm-D (ELM) case 28: // Comm-D (ELM) case 29: // Comm-D (ELM) case 30: // Comm-D (ELM) case 31: // Comm-D (ELM) // These message types use Address/Parity, i.e. our CRC syndrome is the sender's ICAO address. // We can't tell if the CRC is correct or not as we don't know the correct address. // Accept the message if it appears to be from a previously-seen aircraft if (!icaoFilterTest(mm->crc)) { return -1; } mm->source = SOURCE_MODE_S; mm->addr = mm->crc; break; case 11: // All-call reply // This message type uses Parity/Interrogator, i.e. our CRC syndrome is CL + IC from the uplink message // which we can't see. So we don't know if the CRC is correct or not. // // however! CL + IC only occupy the lower 7 bits of the CRC. So if we ignore those bits when testing // the CRC we can still try to detect/correct errors. mm->IID = mm->crc & 0x7f; if (mm->crc & 0xffff80) { int addr; struct errorinfo *ei = modesChecksumDiagnose(mm->crc & 0xffff80, mm->msgbits); if (!ei) { return -2; // couldn't fix it } // see crc.c comments: we do not attempt to fix // more than single-bit errors, as two-bit // errors are ambiguous in DF11. if (ei->errors > 1) return -2; // can't correct errors mm->correctedbits = ei->errors; modesChecksumFix(msg, ei); // check whether the corrected message looks sensible // we are conservative here: only accept corrected messages that // match an existing aircraft. addr = getbits(msg, 9, 32); if (!icaoFilterTest(addr)) { return -1; } } mm->source = SOURCE_MODE_S_CHECKED; break; case 17: // Extended squitter case 18: { // Extended squitter/non-transponder struct errorinfo *ei; int addr1, addr2; // These message types use Parity/Interrogator, but are specified to set II=0 if (mm->crc != 0) { ei = modesChecksumDiagnose(mm->crc, mm->msgbits); if (!ei) { return -2; // couldn't fix it } addr1 = getbits(msg, 9, 32); mm->correctedbits = ei->errors; modesChecksumFix(msg, ei); addr2 = getbits(msg, 9, 32); // we are conservative here: only accept corrected messages that // match an existing aircraft. if (addr1 != addr2 && !icaoFilterTest(addr2)) { return -1; } } mm->source = SOURCE_ADSB; // TIS-B decoding will override this if needed break; } case 20: // Comm-B, altitude reply case 21: // Comm-B, identity reply // These message types either use Address/Parity (see DF0 etc) // or Data Parity where the requested BDS is also xored into the top byte. // So not only do we not know whether the CRC is right, we also don't know if // the ICAO is right! Ow. // Try an exact match if (icaoFilterTest(mm->crc)) { // OK. mm->source = SOURCE_MODE_S; mm->addr = mm->crc; break; } // BDS / overlay control just doesn't work out. return -1; // no good default: // All other message types, we don't know how to handle their CRCs, give up return -2; } // decode the bulk of the message // AA (Address announced) if (mm->msgtype == 11 || mm->msgtype == 17 || mm->msgtype == 18) { mm->AA = mm->addr = getbits(msg, 9, 32); } // AC (Altitude Code) if (mm->msgtype == 0 || mm->msgtype == 4 || mm->msgtype == 16 || mm->msgtype == 20) { mm->AC = getbits(msg, 20, 32); if (mm->AC) { // Only attempt to decode if a valid (non zero) altitude is present mm->altitude_baro = decodeAC13Field(mm->AC, &mm->altitude_baro_unit); if (mm->altitude_baro != INVALID_ALTITUDE) mm->altitude_baro_valid = 1; } } // AF (DF19 Application Field) not decoded // CA (Capability) if (mm->msgtype == 11 || mm->msgtype == 17) { mm->CA = getbits(msg, 6, 8); switch (mm->CA) { case 0: mm->airground = AG_UNCERTAIN; break; case 4: mm->airground = AG_GROUND; break; case 5: mm->airground = AG_AIRBORNE; break; case 6: mm->airground = AG_UNCERTAIN; break; case 7: mm->airground = AG_UNCERTAIN; break; } } // CC (Cross-link capability) if (mm->msgtype == 0) { mm->CC = getbit(msg, 7); } // CF (Control field, see Figure 2-2 ADS-B Message BaselineFormat Structure) if (mm->msgtype == 18) { mm->CF = getbits(msg, 6, 8); } // DR (Downlink Request) if (mm->msgtype == 4 || mm->msgtype == 5 || mm->msgtype == 20 || mm->msgtype == 21) { mm->DR = getbits(msg, 9, 13); } // FS (Flight Status) if (mm->msgtype == 4 || mm->msgtype == 5 || mm->msgtype == 20 || mm->msgtype == 21) { mm->FS = getbits(msg, 6, 8); mm->alert_valid = 1; mm->spi_valid = 1; switch (mm->FS) { case 0: mm->airground = AG_UNCERTAIN; break; case 1: mm->airground = AG_GROUND; break; case 2: mm->airground = AG_UNCERTAIN; mm->alert = 1; break; case 3: mm->airground = AG_GROUND; mm->alert = 1; break; case 4: mm->airground = AG_UNCERTAIN; mm->alert = 1; mm->spi = 1; break; case 5: mm->airground = AG_UNCERTAIN; mm->spi = 1; break; default: mm->spi_valid = 0; mm->alert_valid = 0; break; } } // ID (Identity) if (mm->msgtype == 5 || mm->msgtype == 21) { // Gillham encoded Squawk mm->ID = getbits(msg, 20, 32); if (mm->ID) { mm->squawk = decodeID13Field(mm->ID); mm->squawk_valid = 1; } } // KE (Control, ELM) if (mm->msgtype >= 24 && mm->msgtype <= 31) { mm->KE = getbit(msg, 4); } // MB (messsage, Comm-B) if (mm->msgtype == 20 || mm->msgtype == 21) { memcpy(mm->MB, &msg[4], 7); decodeCommB(mm); } // MD (message, Comm-D) if (mm->msgtype >= 24 && mm->msgtype <= 31) { memcpy(mm->MD, &msg[1], 10); } // ME (message, extended squitter) if (mm->msgtype == 17 || mm->msgtype == 18) { memcpy(mm->ME, &msg[4], 7); decodeExtendedSquitter(mm); } // MV (message, ACAS) if (mm->msgtype == 16) { memcpy(mm->MV, &msg[4], 7); } // ND (number of D-segment, Comm-D) if (mm->msgtype >= 24 && mm->msgtype <= 31) { mm->ND = getbits(msg, 5, 8); } // RI (Reply information, ACAS) if (mm->msgtype == 0 || mm->msgtype == 16) { mm->RI = getbits(msg, 14, 17); } // SL (Sensitivity level, ACAS) if (mm->msgtype == 0 || mm->msgtype == 16) { mm->SL = getbits(msg, 9, 11); } // UM (Utility Message) if (mm->msgtype == 4 || mm->msgtype == 5 || mm->msgtype == 20 || mm->msgtype == 21) { mm->UM = getbits(msg, 14, 19); } // VS (Vertical Status) if (mm->msgtype == 0 || mm->msgtype == 16) { mm->VS = getbit(msg, 6); if (mm->VS) mm->airground = AG_GROUND; else mm->airground = AG_UNCERTAIN; } if (!mm->correctedbits && (mm->msgtype == 17 || (mm->msgtype == 11 && mm->IID == 0))) { // No CRC errors seen, and either it was an DF17 extended squitter // or a DF11 acquisition squitter with II = 0. We probably have the right address. // Don't do this for DF18, as a DF18 transmitter doesn't necessarily have a // Mode S transponder. // NB this is the only place that adds addresses! icaoFilterAdd(mm->addr); } // MLAT overrides all other sources if (mm->remote && mm->timestampMsg == MAGIC_MLAT_TIMESTAMP) mm->source = SOURCE_MLAT; // all done return 0; } static void decodeESIdentAndCategory(struct modesMessage *mm) { // Aircraft Identification and Category unsigned char *me = mm->ME; mm->mesub = getbits(me, 6, 8); mm->callsign[0] = ais_charset[getbits(me, 9, 14)]; mm->callsign[1] = ais_charset[getbits(me, 15, 20)]; mm->callsign[2] = ais_charset[getbits(me, 21, 26)]; mm->callsign[3] = ais_charset[getbits(me, 27, 32)]; mm->callsign[4] = ais_charset[getbits(me, 33, 38)]; mm->callsign[5] = ais_charset[getbits(me, 39, 44)]; mm->callsign[6] = ais_charset[getbits(me, 45, 50)]; mm->callsign[7] = ais_charset[getbits(me, 51, 56)]; mm->callsign[8] = 0; mm->callsign_valid = 1; // actually valid? for (unsigned i = 0; i < 8; ++i) { if (!(mm->callsign[i] >= 'A' && mm->callsign[i] <= 'Z') && !(mm->callsign[i] >= '0' && mm->callsign[i] <= '9') && mm->callsign[i] != ' ') { // Bad callsign, ignore it mm->callsign_valid = 0; break; } } mm->category = ((0x0E - mm->metype) << 4) | mm->mesub; mm->category_valid = 1; } // Handle setting a non-ICAO address static void setIMF(struct modesMessage *mm) { mm->addr |= MODES_NON_ICAO_ADDRESS; switch (mm->addrtype) { case ADDR_ADSB_ICAO: case ADDR_ADSB_ICAO_NT: // Shouldn't happen, but let's try to handle it mm->addrtype = ADDR_ADSB_OTHER; break; case ADDR_TISB_ICAO: mm->addrtype = ADDR_TISB_TRACKFILE; break; case ADDR_ADSR_ICAO: mm->addrtype = ADDR_ADSR_OTHER; break; default: // Nothing. break; } } static void decodeESAirborneVelocity(struct modesMessage *mm, int check_imf) { // Airborne Velocity Message unsigned char *me = mm->ME; // 1-5: ME type // 6-8: ME subtype mm->mesub = getbits(me, 6, 8); if (mm->mesub < 1 || mm->mesub > 4) return; // 9: IMF or Intent Change if (check_imf && getbit(me, 9)) setIMF(mm); // 10: reserved // 11-13: NACv (NUCr in v0, maps directly to NACv in v2) mm->accuracy.nac_v_valid = 1; mm->accuracy.nac_v = getbits(me, 11, 13); // 14-35: speed/velocity depending on subtype switch (mm->mesub) { case 1: case 2: { // 14: E/W direction // 15-24: E/W speed // 25: N/S direction // 26-35: N/S speed unsigned ew_raw = getbits(me, 15, 24); unsigned ns_raw = getbits(me, 26, 35); if (ew_raw && ns_raw) { int ew_vel = (ew_raw - 1) * (getbit(me, 14) ? -1 : 1) * ((mm->mesub == 2) ? 4 : 1); int ns_vel = (ns_raw - 1) * (getbit(me, 25) ? -1 : 1) * ((mm->mesub == 2) ? 4 : 1); // Compute velocity and angle from the two speed components mm->gs.v0 = mm->gs.v2 = mm->gs.selected = sqrtf((ns_vel * ns_vel) + (ew_vel * ew_vel) + 0.5); mm->gs_valid = 1; if (mm->gs.selected > 0) { float ground_track = atan2(ew_vel, ns_vel) * 180.0 / M_PI; // We don't want negative values but a 0-360 scale if (ground_track < 0) ground_track += 360; mm->heading = ground_track; mm->heading_type = HEADING_GROUND_TRACK; mm->heading_valid = 1; } } break; } case 3: case 4: { // 14: heading status // 15-24: heading if (getbit(me, 14)) { mm->heading_valid = 1; mm->heading = getbits(me, 15, 24) * 360.0 / 1024.0; mm->heading_type = HEADING_MAGNETIC_OR_TRUE; } // 25: airspeed type // 26-35: airspeed unsigned airspeed = getbits(me, 26, 35); if (airspeed) { unsigned speed = (airspeed - 1) * (mm->mesub == 4 ? 4 : 1); if (getbit(me, 25)) { mm->tas_valid = 1; mm->tas = speed; } else { mm->ias_valid = 1; mm->ias = speed; } } break; } } // 36: vert rate source // 37: vert rate sign // 38-46: vert rate magnitude unsigned vert_rate = getbits(me, 38, 46); unsigned vert_rate_is_baro = getbit(me, 36); if (vert_rate) { int rate = (vert_rate - 1) * (getbit(me, 37) ? -64 : 64); if (vert_rate_is_baro) { mm->baro_rate = rate; mm->baro_rate_valid = 1; } else { mm->geom_rate = rate; mm->geom_rate_valid = 1; } } // 47-48: reserved // 49: baro/geom delta sign // 50-56: baro/geom delta magnitude unsigned raw_delta = getbits(me, 50, 56); if (raw_delta) { mm->geom_delta_valid = 1; mm->geom_delta = (raw_delta - 1) * (getbit(me, 49) ? -25 : 25); } } static void decodeESSurfacePosition(struct modesMessage *mm, int check_imf) { // Surface position and movement unsigned char *me = mm->ME; mm->airground = AG_GROUND; // definitely. mm->cpr_valid = 1; mm->cpr_type = CPR_SURFACE; // 6-12: Movement unsigned movement = getbits(me, 6, 12); if (movement > 0 && movement < 125) { mm->gs_valid = 1; mm->gs.selected = mm->gs.v0 = decodeMovementFieldV0(movement); // assumed v0 until told otherwise mm->gs.v2 = decodeMovementFieldV2(movement); } // 13: Heading/track status // 14-20: Heading/track if (getbit(me, 13)) { mm->heading_valid = 1; mm->heading = getbits(me, 14, 20) * 360.0 / 128.0; mm->heading_type = HEADING_TRACK_OR_HEADING; } // 21: IMF or T flag if (check_imf && getbit(me, 21)) setIMF(mm); // 22: F flag (odd/even) mm->cpr_odd = getbit(me, 22); // 23-39: CPR encoded latitude mm->cpr_lat = getbits(me, 23, 39); // 40-56: CPR encoded longitude mm->cpr_lon = getbits(me, 40, 56); } static void decodeESAirbornePosition(struct modesMessage *mm, int check_imf) { // Airborne position and altitude unsigned char *me = mm->ME; // 6-7: surveillance status switch (getbits(me, 6, 7)) { case 0: // no status mm->alert_valid = mm->spi_valid = 1; mm->alert = mm->spi = 0; break; case 1: // permanent alert case 2: // temporary alert mm->alert_valid = 1; mm->alert = 1; // states 1/2 override state 3, so we don't know SPI status here. break; case 3: // SPI // we know there's no alert in this case mm->alert_valid = mm->spi_valid = 1; mm->alert = 0; mm->spi = 1; break; } // 8: IMF or NIC supplement-B if (check_imf) { if (getbit(me, 8)) setIMF(mm); } else { // NIC-B (v2) or SAF (v0/v1) mm->accuracy.nic_b_valid = 1; mm->accuracy.nic_b = getbit(me, 8); } // 9-20: altitude unsigned AC12Field = getbits(me, 9, 20); if (mm->metype == 0) { // no position information } else { // 21: T flag (UTC sync or not) // 22: F flag (odd or even) // 23-39: CPR encoded latitude // 40-56: CPR encoded longitude mm->cpr_lat = getbits(me, 23, 39); mm->cpr_lon = getbits(me, 40, 56); // Catch some common failure modes and don't mark them as valid // (so they won't be used for positioning) if (AC12Field == 0 && mm->cpr_lon == 0 && (mm->cpr_lat & 0x0fff) == 0 && mm->metype == 15) { // Seen from at least: // 400F3F (Eurocopter ECC155 B1) - Bristow Helicopters // 4008F3 (BAE ATP) - Atlantic Airlines // 400648 (BAE ATP) - Atlantic Airlines // altitude == 0, longitude == 0, type == 15 and zeros in latitude LSB. // Can alternate with valid reports having type == 14 Modes.stats_current.cpr_filtered++; } else { // Otherwise, assume it's valid. mm->cpr_valid = 1; mm->cpr_type = CPR_AIRBORNE; mm->cpr_odd = getbit(me, 22); } } if (AC12Field && mm->airground != AG_GROUND) {// Only attempt to decode if a valid (non zero) altitude is present and not on ground altitude_unit_t unit; int alt = decodeAC12Field(AC12Field, &unit); if (alt != INVALID_ALTITUDE) { if (mm->metype == 20 || mm->metype == 21 || mm->metype == 22) { mm->altitude_geom = alt; mm->altitude_geom_unit = unit; mm->altitude_geom_valid = 1; } else { mm->altitude_baro = alt; mm->altitude_baro_unit = unit; mm->altitude_baro_valid = 1; } } } } static void decodeESTestMessage(struct modesMessage *mm) { unsigned char *me = mm->ME; mm->mesub = getbits(me, 6, 8); if (mm->mesub == 7) { // (see 1090-WP-15-20) int ID13Field = getbits(me, 9, 21); if (ID13Field) { mm->squawk_valid = 1; mm->squawk = decodeID13Field(ID13Field); } } } static void decodeESAircraftStatus(struct modesMessage *mm, int check_imf) { // Extended Squitter Aircraft Status unsigned char *me = mm->ME; mm->mesub = getbits(me, 6, 8); if (mm->mesub == 1) { // Emergency status squawk field mm->emergency_valid = 1; mm->emergency = (emergency_t) getbits(me, 9, 11); unsigned ID13Field = getbits(me, 12, 24); if (ID13Field) { mm->squawk_valid = 1; mm->squawk = decodeID13Field(ID13Field); } if (check_imf && getbit(me, 56)) setIMF(mm); } } static void decodeESTargetStatus(struct modesMessage *mm, int check_imf) { unsigned char *me = mm->ME; mm->mesub = getbits(me, 6, 7); // an unusual message: only 2 bits of subtype if (check_imf && getbit(me, 51)) setIMF(mm); if (mm->mesub == 0 && getbit(me, 11) == 0) { // Target state and status, V1 // 8-9: vertical source switch (getbits(me, 8, 9)) { case 1: mm->nav.altitude_source = NAV_ALT_MCP; break; case 2: mm->nav.altitude_source = NAV_ALT_AIRCRAFT; break; case 3: mm->nav.altitude_source = NAV_ALT_FMS; break; default: // nothing break; } // 10: target altitude type (MSL or Baro, ignored) // 11: backward compatibility bit, always 0 // 12-13: target alt capabilities (ignored) // 14-15: vertical mode switch (getbits(me, 14, 15)) { case 1: // "acquiring" mm->nav.modes_valid = 1; if (mm->nav.altitude_source == NAV_ALT_FMS) { mm->nav.modes |= NAV_MODE_VNAV; } else { mm->nav.modes |= NAV_MODE_AUTOPILOT; } break; case 2: // "maintaining" mm->nav.modes_valid = 1; if (mm->nav.altitude_source == NAV_ALT_FMS) { mm->nav.modes |= NAV_MODE_VNAV; } else if (mm->nav.altitude_source == NAV_ALT_AIRCRAFT) { mm->nav.modes |= NAV_MODE_ALT_HOLD; } else { mm->nav.modes |= NAV_MODE_AUTOPILOT; } break; default: // nothing break; } // 16-25: target altitude int alt = -1000 + 100 * getbits(me, 16, 25); switch (mm->nav.altitude_source) { case NAV_ALT_MCP: mm->nav.mcp_altitude_valid = 1; mm->nav.mcp_altitude = alt; break; case NAV_ALT_FMS: mm->nav.fms_altitude_valid = 1; mm->nav.fms_altitude = alt; break; default: // nothing break; } // 26-27: horizontal data source unsigned h_source = getbits(me, 26, 27); if (h_source != 0) { // 28-36: target heading/track mm->nav.heading_valid = 1; mm->nav.heading = getbits(me, 28, 36); // 37: track vs heading if (getbit(me, 37)) { mm->nav.heading_type = HEADING_GROUND_TRACK; } else { mm->nav.heading_type = HEADING_MAGNETIC_OR_TRUE; } } // 38-39: horizontal mode switch (getbits(me, 38, 39)) { case 1: // acquiring case 2: // maintaining mm->nav.modes_valid = 1; if (h_source == 3) { // FMS mm->nav.modes |= NAV_MODE_LNAV; } else { mm->nav.modes |= NAV_MODE_AUTOPILOT; } break; default: // nothing break; } // 40-43: NACp mm->accuracy.nac_p_valid = 1; mm->accuracy.nac_p = getbits(me, 40, 43); // 44: NICbaro mm->accuracy.nic_baro_valid = 1; mm->accuracy.nic_baro = getbit(me, 44); // 45-46: SIL mm->accuracy.sil = getbits(me, 45, 46); mm->accuracy.sil_type = SIL_UNKNOWN; // 47-51: reserved // 52-53: TCAS status switch (getbits(me, 52, 53)) { case 1: mm->nav.modes_valid = 1; // no tcas break; case 2: case 3: mm->nav.modes_valid = 1; mm->nav.modes |= NAV_MODE_TCAS; break; case 0: // assume TCAS if we had any other modes // but don't enable modes just for this mm->nav.modes |= NAV_MODE_TCAS; break; default: // nothing break; } // 54-56: emergency/priority mm->emergency_valid = 1; mm->emergency = (emergency_t) getbits(me, 54, 56); } else if (mm->mesub == 1) { // Target state and status, V2 // 8: SIL unsigned is_fms = getbit(me, 9); unsigned alt_bits = getbits(me, 10, 20); if (alt_bits != 0) { if (is_fms) { mm->nav.fms_altitude_valid = 1; mm->nav.fms_altitude = (alt_bits - 1) * 32; } else { mm->nav.mcp_altitude_valid = 1; mm->nav.mcp_altitude = (alt_bits - 1) * 32; } } unsigned baro_bits = getbits(me, 21, 29); if (baro_bits != 0) { mm->nav.qnh_valid = 1; mm->nav.qnh = 800.0 + (baro_bits - 1) * 0.8; } if (getbit(me, 30)) { mm->nav.heading_valid = 1; // two's complement -180..+180, which is conveniently // also the same as unsigned 0..360 mm->nav.heading = getbits(me, 31, 39) * 180.0 / 256.0; mm->nav.heading_type = HEADING_MAGNETIC_OR_TRUE; } // 40-43: NACp mm->accuracy.nac_p_valid = 1; mm->accuracy.nac_p = getbits(me, 40, 43); // 44: NICbaro mm->accuracy.nic_baro_valid = 1; mm->accuracy.nic_baro = getbit(me, 44); // 45-46: SIL mm->accuracy.sil = getbits(me, 45, 46); mm->accuracy.sil_type = SIL_UNKNOWN; // 47: mode bits validity if (getbit(me, 47)) { // 48-54: mode bits mm->nav.modes_valid = 1; mm->nav.modes = (getbit(me, 48) ? NAV_MODE_AUTOPILOT : 0) | (getbit(me, 49) ? NAV_MODE_VNAV : 0) | (getbit(me, 50) ? NAV_MODE_ALT_HOLD : 0) | // 51: IMF (getbit(me, 52) ? NAV_MODE_APPROACH : 0) | (getbit(me, 53) ? NAV_MODE_TCAS : 0) | (getbit(me, 54) ? NAV_MODE_LNAV : 0); } // 55-56 reserved } } static void decodeESOperationalStatus(struct modesMessage *mm, int check_imf) { unsigned char *me = mm->ME; mm->mesub = getbits(me, 6, 8); // Aircraft Operational Status if (check_imf && getbit(me, 56)) setIMF(mm); if (mm->mesub == 0 || mm->mesub == 1) { mm->opstatus.valid = 1; mm->opstatus.version = getbits(me, 41, 43); switch (mm->opstatus.version) { case 0: if (mm->mesub == 0 && getbits(me, 9, 10) == 0) { mm->opstatus.cc_acas = !getbit(me, 12); mm->opstatus.cc_cdti = getbit(me, 13); } break; case 1: if (getbits(me, 25, 26) == 0) { mm->opstatus.om_acas_ra = getbit(me, 27); mm->opstatus.om_ident = getbit(me, 28); mm->opstatus.om_atc = getbit(me, 29); } if (mm->mesub == 0 && getbits(me, 9, 10) == 0 && getbits(me, 13, 14) == 0) { // airborne mm->opstatus.cc_acas = !getbit(me, 11); mm->opstatus.cc_cdti = getbit(me, 12); mm->opstatus.cc_arv = getbit(me, 15); mm->opstatus.cc_ts = getbit(me, 16); mm->opstatus.cc_tc = getbits(me, 17, 18); } else if (mm->mesub == 1 && getbits(me, 9, 10) == 0 && getbits(me, 13, 14) == 0) { // surface mm->opstatus.cc_poa = getbit(me, 11); mm->opstatus.cc_cdti = getbit(me, 12); mm->opstatus.cc_b2_low = getbit(me, 15); mm->opstatus.cc_lw_valid = 1; mm->opstatus.cc_lw = getbits(me, 21, 24); } mm->accuracy.nic_a_valid = 1; mm->accuracy.nic_a = getbit(me, 44); mm->accuracy.nac_p_valid = 1; mm->accuracy.nac_p = getbits(me, 45, 48); mm->accuracy.sil_type = SIL_UNKNOWN; mm->accuracy.sil = getbits(me, 51, 52); mm->opstatus.hrd = getbit(me, 54) ? HEADING_MAGNETIC : HEADING_TRUE; if (mm->mesub == 0) { mm->accuracy.nic_baro_valid = 1; mm->accuracy.nic_baro = getbit(me, 53); } else { mm->opstatus.tah = getbit(me, 53) ? HEADING_GROUND_TRACK : mm->opstatus.hrd; } break; case 2: if (getbits(me, 25, 26) == 0) { mm->opstatus.om_acas_ra = getbit(me, 27); mm->opstatus.om_ident = getbit(me, 28); mm->opstatus.om_atc = getbit(me, 29); mm->opstatus.om_saf = getbit(me, 30); mm->accuracy.sda_valid = 1; mm->accuracy.sda = getbits(me, 31, 32); } if (mm->mesub == 0 && getbits(me, 9, 10) == 0) { // airborne mm->opstatus.cc_acas = getbit(me, 11); // nb inverted sense versus v0/v1 mm->opstatus.cc_1090_in = getbit(me, 12); mm->opstatus.cc_arv = getbit(me, 15); mm->opstatus.cc_ts = getbit(me, 16); mm->opstatus.cc_tc = getbits(me, 17, 18); mm->opstatus.cc_uat_in = getbit(me, 19); } else if (mm->mesub == 1 && getbits(me, 9, 10) == 0) { // surface mm->opstatus.cc_poa = getbit(me, 11); mm->opstatus.cc_1090_in = getbit(me, 12); mm->opstatus.cc_b2_low = getbit(me, 15); mm->opstatus.cc_uat_in = getbit(me, 16); mm->accuracy.nac_v_valid = 1; mm->accuracy.nac_v = getbits(me, 17, 19); mm->accuracy.nic_c_valid = 1; mm->accuracy.nic_c = getbit(me, 20); mm->opstatus.cc_lw_valid = 1; mm->opstatus.cc_lw = getbits(me, 21, 24); mm->opstatus.cc_antenna_offset = getbits(me, 33, 40); } mm->accuracy.nic_a_valid = 1; mm->accuracy.nic_a = getbit(me, 44); mm->accuracy.nac_p_valid = 1; mm->accuracy.nac_p = getbits(me, 45, 48); mm->accuracy.sil = getbits(me, 51, 52); mm->accuracy.sil_type = getbit(me, 55) ? SIL_PER_SAMPLE : SIL_PER_HOUR; mm->opstatus.hrd = getbit(me, 54) ? HEADING_MAGNETIC : HEADING_TRUE; if (mm->mesub == 0) { mm->accuracy.gva_valid = 1; mm->accuracy.gva = getbits(me, 49, 50); mm->accuracy.nic_baro_valid = 1; mm->accuracy.nic_baro = getbit(me, 53); } else { mm->opstatus.tah = getbit(me, 53) ? HEADING_GROUND_TRACK : mm->opstatus.hrd; } break; } } } static void decodeExtendedSquitter(struct modesMessage *mm) { unsigned char *me = mm->ME; unsigned metype = mm->metype = getbits(me, 1, 5); unsigned check_imf = 0; // Check CF on DF18 to work out the format of the ES and whether we need to look for an IMF bit if (mm->msgtype == 18) { switch (mm->CF) { case 0: // ADS-B Message from a non-transponder device, AA field holds 24-bit ICAO aircraft address mm->addrtype = ADDR_ADSB_ICAO_NT; break; case 1: // Reserved for ADS-B Message in which the AA field holds anonymous address or ground vehicle address or fixed obstruction address mm->addrtype = ADDR_ADSB_OTHER; mm->addr |= MODES_NON_ICAO_ADDRESS; break; case 2: // Fine TIS-B Message // IMF=0: AA field contains the 24-bit ICAO aircraft address // IMF=1: AA field contains the 12-bit Mode A code followed by a 12-bit track file number mm->source = SOURCE_TISB; mm->addrtype = ADDR_TISB_ICAO; check_imf = 1; break; case 3: // Coarse TIS-B airborne position and velocity. // IMF=0: AA field contains the 24-bit ICAO aircraft address // IMF=1: AA field contains the 12-bit Mode A code followed by a 12-bit track file number // For now we only look at the IMF bit. mm->source = SOURCE_TISB; mm->addrtype = ADDR_TISB_ICAO; if (getbit(me, 1)) setIMF(mm); return; case 5: // Fine TIS-B Message, AA field contains a non-ICAO 24-bit address mm->addrtype = ADDR_TISB_OTHER; mm->source = SOURCE_TISB; mm->addr |= MODES_NON_ICAO_ADDRESS; break; case 6: // Rebroadcast of ADS-B Message from an alternate data link // IMF=0: AA field holds 24-bit ICAO aircraft address // IMF=1: AA field holds anonymous address or ground vehicle address or fixed obstruction address mm->addrtype = ADDR_ADSR_ICAO; check_imf = 1; break; default: // All others, we don't know the format. mm->addrtype = ADDR_UNKNOWN; mm->addr |= MODES_NON_ICAO_ADDRESS; // assume non-ICAO return; } } switch (metype) { case 1: case 2: case 3: case 4: decodeESIdentAndCategory(mm); break; case 19: decodeESAirborneVelocity(mm, check_imf); break; case 5: case 6: case 7: case 8: decodeESSurfacePosition(mm, check_imf); break; case 0: // Airborne position, baro altitude only case 9: case 10: case 11: case 12: case 13: case 14: case 15: case 16: case 17: case 18: // Airborne position, baro case 20: case 21: case 22: // Airborne position, geometric altitude (HAE or MSL) decodeESAirbornePosition(mm, check_imf); break; case 23: decodeESTestMessage(mm); break; case 24: // Reserved for Surface System Status break; case 28: decodeESAircraftStatus(mm, check_imf); break; case 29: decodeESTargetStatus(mm, check_imf); break; case 30: // Aircraft Operational Coordination break; case 31: decodeESOperationalStatus(mm, check_imf); break; default: break; } } static const char *df_names[33] = { /* 0 */ "Short Air-Air Surveillance", /* 1 */ NULL, /* 2 */ NULL, /* 3 */ NULL, /* 4 */ "Survelliance, Altitude Reply", /* 5 */ "Survelliance, Identity Reply", /* 6 */ NULL, /* 7 */ NULL, /* 8 */ NULL, /* 9 */ NULL, /* 10 */ NULL, /* 11 */ "All Call Reply", /* 12 */ NULL, /* 13 */ NULL, /* 14 */ NULL, /* 15 */ NULL, /* 16 */ "Long Air-Air ACAS", /* 17 */ "Extended Squitter", /* 18 */ "Extended Squitter (Non-Transponder)", /* 19 */ "Extended Squitter (Military)", /* 20 */ "Comm-B, Altitude Reply", /* 21 */ "Comm-B, Identity Reply", /* 22 */ "Military Use", /* 23 */ NULL, /* 24 */ "Comm-D Extended Length Message", /* 25 */ "Comm-D Extended Length Message", /* 26 */ "Comm-D Extended Length Message", /* 27 */ "Comm-D Extended Length Message", /* 28 */ "Comm-D Extended Length Message", /* 29 */ "Comm-D Extended Length Message", /* 30 */ "Comm-D Extended Length Message", /* 31 */ "Comm-D Extended Length Message", /* 32 */ "Mode A/C Reply", }; static const char *df_to_string(unsigned df) { if (df > 32) return "out of range"; if (!df_names[df]) return "reserved"; return df_names[df]; } static const char *altitude_unit_to_string(altitude_unit_t unit) { switch (unit) { case UNIT_FEET: return "ft"; case UNIT_METERS: return "m"; default: return "(unknown altitude unit)"; } } static const char *airground_to_string(airground_t airground) { switch (airground) { case AG_GROUND: return "ground"; case AG_AIRBORNE: return "airborne"; case AG_INVALID: return "invalid"; case AG_UNCERTAIN: return "airborne?"; default: return "(unknown airground state)"; } } static const char *addrtype_to_string(addrtype_t type) { switch (type) { case ADDR_ADSB_ICAO: return "Mode S / ADS-B"; case ADDR_ADSB_ICAO_NT: return "ADS-B, non-transponder"; case ADDR_ADSB_OTHER: return "ADS-B, other addressing scheme"; case ADDR_TISB_ICAO: return "TIS-B"; case ADDR_TISB_OTHER: return "TIS-B, other addressing scheme"; case ADDR_TISB_TRACKFILE: return "TIS-B, Mode A code and track file number"; case ADDR_ADSR_ICAO: return "ADS-R"; case ADDR_ADSR_OTHER: return "ADS-R, other addressing scheme"; case ADDR_MODE_A: return "Mode A"; default: return "unknown addressing scheme"; } } static const char *cpr_type_to_string(cpr_type_t type) { switch (type) { case CPR_SURFACE: return "Surface"; case CPR_AIRBORNE: return "Airborne"; case CPR_COARSE: return "TIS-B Coarse"; default: return "unknown CPR type"; } } static const char *heading_type_to_string(heading_type_t type) { switch (type) { case HEADING_GROUND_TRACK: return "Ground track"; case HEADING_MAGNETIC: return "Mag heading"; case HEADING_TRUE: return "True heading"; case HEADING_MAGNETIC_OR_TRUE: return "Heading"; case HEADING_TRACK_OR_HEADING: return "Track/Heading"; default: return "unknown heading type"; } } static const char *commb_format_to_string(commb_format_t format) { switch (format) { case COMMB_EMPTY_RESPONSE: return "empty response"; case COMMB_AMBIGUOUS: return "ambiguous format"; case COMMB_DATALINK_CAPS: return "BDS1,0 Datalink capabilities"; case COMMB_GICB_CAPS: return "BDS1,7 Common usage GICB capabilities"; case COMMB_AIRCRAFT_IDENT: return "BDS2,0 Aircraft identification"; case COMMB_ACAS_RA: return "BDS3,0 ACAS resolution advisory"; case COMMB_VERTICAL_INTENT: return "BDS4,0 Selected vertical intention"; case COMMB_TRACK_TURN: return "BDS5,0 Track and turn report"; case COMMB_HEADING_SPEED: return "BDS6,0 Heading and speed report"; default: return "unknown format"; } } static const char *nav_modes_to_string(nav_modes_t flags) { static char buf[128]; buf[0] = 0; if (flags & NAV_MODE_AUTOPILOT) strcat(buf, "autopilot "); if (flags & NAV_MODE_VNAV) strcat(buf, "vnav "); if (flags & NAV_MODE_ALT_HOLD) strcat(buf, "althold "); if (flags & NAV_MODE_APPROACH) strcat(buf, "approach "); if (flags & NAV_MODE_LNAV) strcat(buf, "lnav "); if (flags & NAV_MODE_TCAS) strcat(buf, "tcas "); if (buf[0] != 0) buf[strlen(buf)-1] = 0; return buf; } static const char *sil_type_to_string(sil_type_t type) { switch (type) { case SIL_UNKNOWN: return "unknown type"; case SIL_PER_HOUR: return "per flight hour"; case SIL_PER_SAMPLE: return "per sample"; default: return "invalid type"; } } static const char *emergency_to_string(emergency_t emergency) { switch (emergency) { case EMERGENCY_NONE: return "no emergency"; case EMERGENCY_GENERAL: return "general emergency (7700)"; case EMERGENCY_LIFEGUARD: return "lifeguard / medical emergency"; case EMERGENCY_MINFUEL: return "minimum fuel"; case EMERGENCY_NORDO: return "no communications (7600)"; case EMERGENCY_UNLAWFUL: return "unlawful interference (7500)"; case EMERGENCY_DOWNED: return "downed aircraft"; default: return "reserved"; } } static void print_hex_bytes(unsigned char *data, size_t len) { size_t i; for (i = 0; i < len; ++i) { printf("%02X", (unsigned)data[i]); } } static int esTypeHasSubtype(unsigned metype) { if (metype <= 18) { return 0; } if (metype >= 20 && metype <= 22) { return 0; } return 1; } static const char *esTypeName(unsigned metype, unsigned mesub) { switch (metype) { case 0: return "No position information (airborne or surface)"; case 1: case 2: case 3: case 4: return "Aircraft identification and category"; case 5: case 6: case 7: case 8: return "Surface position"; case 9: case 10: case 11: case 12: case 13: case 14: case 15: case 16: case 17: case 18: return "Airborne position (barometric altitude)"; case 19: switch (mesub) { case 1: return "Airborne velocity over ground, subsonic"; case 2: return "Airborne velocity over ground, supersonic"; case 3: return "Airspeed and heading, subsonic"; case 4: return "Airspeed and heading, supersonic"; default: return "Unknown"; } case 20: case 21: case 22: return "Airborne position (geometric altitude)"; case 23: switch (mesub) { case 0: return "Test message"; case 7: return "National use / 1090-WP-15-20 Mode A squawk"; default: return "Unknown"; } case 24: return "Reserved for surface system status"; case 27: return "Reserved for trajectory change"; case 28: switch (mesub) { case 1: return "Emergency/priority status"; case 2: return "ACAS RA broadcast"; default: return "Unknown"; } case 29: switch (mesub) { case 0: return "Target state and status (V1)"; case 1: return "Target state and status (V2)"; default: return "Unknown"; } case 30: return "Aircraft Operational Coordination"; case 31: // Aircraft Operational Status switch (mesub) { case 0: return "Aircraft operational status (airborne)"; case 1: return "Aircraft operational status (surface)"; default: return "Unknown"; } default: return "Unknown"; } } void displayModesMessage(struct modesMessage *mm) { int j; // Handle only addresses mode first. if (Modes.onlyaddr) { printf("%06x\n", mm->addr); return; // Enough for --onlyaddr mode } // Show the raw message. if (Modes.mlat && mm->timestampMsg) { printf("@%012" PRIX64, mm->timestampMsg); } else printf("*"); for (j = 0; j < mm->msgbits/8; j++) printf("%02x", mm->msg[j]); printf(";\n"); if (Modes.raw) { fflush(stdout); // Provide data to the reader ASAP return; // Enough for --raw mode } if (mm->msgtype < 32) printf("CRC: %06x\n", mm->crc); if (mm->correctedbits != 0) printf("No. of bit errors fixed: %d\n", mm->correctedbits); if (mm->signalLevel > 0) printf("RSSI: %.1f dBFS\n", 10 * log10(mm->signalLevel)); if (mm->score) printf("Score: %d\n", mm->score); if (mm->timestampMsg) { if (mm->timestampMsg == MAGIC_MLAT_TIMESTAMP) printf("This is a synthetic MLAT message.\n"); else printf("Time: %.2fus\n", mm->timestampMsg / 12.0); } switch (mm->msgtype) { case 0: printf("DF:0 addr:%06X VS:%u CC:%u SL:%u RI:%u AC:%u\n", mm->addr, mm->VS, mm->CC, mm->SL, mm->RI, mm->AC); break; case 4: printf("DF:4 addr:%06X FS:%u DR:%u UM:%u AC:%u\n", mm->addr, mm->FS, mm->DR, mm->UM, mm->AC); break; case 5: printf("DF:5 addr:%06X FS:%u DR:%u UM:%u ID:%u\n", mm->addr, mm->FS, mm->DR, mm->UM, mm->ID); break; case 11: printf("DF:11 AA:%06X IID:%u CA:%u\n", mm->AA, mm->IID, mm->CA); break; case 16: printf("DF:16 addr:%06x VS:%u SL:%u RI:%u AC:%u MV:", mm->addr, mm->VS, mm->SL, mm->RI, mm->AC); print_hex_bytes(mm->MV, sizeof(mm->MV)); printf("\n"); break; case 17: printf("DF:17 AA:%06X CA:%u ME:", mm->AA, mm->CA); print_hex_bytes(mm->ME, sizeof(mm->ME)); printf("\n"); break; case 18: printf("DF:18 AA:%06X CF:%u ME:", mm->AA, mm->CF); print_hex_bytes(mm->ME, sizeof(mm->ME)); printf("\n"); break; case 20: printf("DF:20 addr:%06X FS:%u DR:%u UM:%u AC:%u MB:", mm->addr, mm->FS, mm->DR, mm->UM, mm->AC); print_hex_bytes(mm->MB, sizeof(mm->MB)); printf("\n"); break; case 21: printf("DF:21 addr:%06x FS:%u DR:%u UM:%u ID:%u MB:", mm->addr, mm->FS, mm->DR, mm->UM, mm->ID); print_hex_bytes(mm->MB, sizeof(mm->MB)); printf("\n"); break; case 24: case 25: case 26: case 27: case 28: case 29: case 30: case 31: printf("DF:24 addr:%06x KE:%u ND:%u MD:", mm->addr, mm->KE, mm->ND); print_hex_bytes(mm->MD, sizeof(mm->MD)); printf("\n"); break; } printf(" %s", df_to_string(mm->msgtype)); if (mm->msgtype == 17 || mm->msgtype == 18) { if (esTypeHasSubtype(mm->metype)) { printf(" %s (%u/%u)", esTypeName(mm->metype, mm->mesub), mm->metype, mm->mesub); } else { printf(" %s (%u)", esTypeName(mm->metype, mm->mesub), mm->metype); } } printf("\n"); if (mm->msgtype == 20 || mm->msgtype == 21) { printf(" Comm-B format: %s\n", commb_format_to_string(mm->commb_format)); } if (mm->addr & MODES_NON_ICAO_ADDRESS) { printf(" Other Address: %06X (%s)\n", mm->addr & 0xFFFFFF, addrtype_to_string(mm->addrtype)); } else { printf(" ICAO Address: %06X (%s)\n", mm->addr, addrtype_to_string(mm->addrtype)); } if (mm->airground != AG_INVALID) { printf(" Air/Ground: %s\n", airground_to_string(mm->airground)); } if (mm->altitude_baro_valid) { printf(" Baro altitude: %d %s\n", mm->altitude_baro, altitude_unit_to_string(mm->altitude_baro_unit)); } if (mm->altitude_geom_valid) { printf(" Geom altitude: %d %s\n", mm->altitude_geom, altitude_unit_to_string(mm->altitude_geom_unit)); } if (mm->geom_delta_valid) { printf(" Geom - baro: %d ft\n", mm->geom_delta); } if (mm->heading_valid) { printf(" %-13s %.1f\n", heading_type_to_string(mm->heading_type), mm->heading); } if (mm->track_rate_valid) { printf(" Track rate: %.2f deg/sec %s\n", mm->track_rate, mm->track_rate < 0 ? "left" : mm->track_rate > 0 ? "right" : ""); } if (mm->roll_valid) { printf(" Roll: %.1f degrees %s\n", mm->roll, mm->roll < -0.05 ? "left" : mm->roll > 0.05 ? "right" : ""); } if (mm->gs_valid) { printf(" Groundspeed: %.1f kt", mm->gs.selected); if (mm->gs.v0 != mm->gs.selected) { printf(" (v0: %.1f kt)", mm->gs.v0); } if (mm->gs.v2 != mm->gs.selected) { printf(" (v2: %.1f kt)", mm->gs.v2); } printf("\n"); } if (mm->ias_valid) { printf(" IAS: %u kt\n", mm->ias); } if (mm->tas_valid) { printf(" TAS: %u kt\n", mm->tas); } if (mm->mach_valid) { printf(" Mach number: %.3f\n", mm->mach); } if (mm->baro_rate_valid) { printf(" Baro rate: %d ft/min\n", mm->baro_rate); } if (mm->geom_rate_valid) { printf(" Geom rate: %d ft/min\n", mm->geom_rate); } if (mm->squawk_valid) { printf(" Squawk: %04x\n", mm->squawk); } if (mm->callsign_valid) { printf(" Ident: %s\n", mm->callsign); } if (mm->category_valid) { printf(" Category: %02X\n", mm->category); } if (mm->cpr_valid) { printf(" CPR type: %s\n" " CPR odd flag: %s\n", cpr_type_to_string(mm->cpr_type), mm->cpr_odd ? "odd" : "even"); if (mm->cpr_decoded) { printf(" CPR latitude: %.5f (%u)\n" " CPR longitude: %.5f (%u)\n" " CPR decoding: %s\n" " NIC: %u\n" " Rc: %.3f km / %.1f NM\n", mm->decoded_lat, mm->cpr_lat, mm->decoded_lon, mm->cpr_lon, mm->cpr_relative ? "local" : "global", mm->decoded_nic, mm->decoded_rc / 1000.0, mm->decoded_rc / 1852.0); } else { printf(" CPR latitude: (%u)\n" " CPR longitude: (%u)\n" " CPR decoding: none\n", mm->cpr_lat, mm->cpr_lon); } } if (mm->accuracy.nic_a_valid) { printf(" NIC-A: %d\n", mm->accuracy.nic_a); } if (mm->accuracy.nic_b_valid) { printf(" NIC-B: %d\n", mm->accuracy.nic_b); } if (mm->accuracy.nic_c_valid) { printf(" NIC-C: %d\n", mm->accuracy.nic_c); } if (mm->accuracy.nic_baro_valid) { printf(" NIC-baro: %d\n", mm->accuracy.nic_baro); } if (mm->accuracy.nac_p_valid) { printf(" NACp: %d\n", mm->accuracy.nac_p); } if (mm->accuracy.nac_v_valid) { printf(" NACv: %d\n", mm->accuracy.nac_v); } if (mm->accuracy.gva_valid) { printf(" GVA: %d\n", mm->accuracy.gva); } if (mm->accuracy.sil_type != SIL_INVALID) { const char *sil_description; switch (mm->accuracy.sil) { case 1: sil_description = "p <= 0.1%"; break; case 2: sil_description = "p <= 0.001%"; break; case 3: sil_description = "p <= 0.00001%"; break; default: sil_description = "p > 0.1%"; break; } printf(" SIL: %d (%s, %s)\n", mm->accuracy.sil, sil_description, sil_type_to_string(mm->accuracy.sil_type)); } if (mm->accuracy.sda_valid) { printf(" SDA: %d\n", mm->accuracy.sda); } if (mm->opstatus.valid) { printf(" Aircraft Operational Status:\n"); printf(" Version: %d\n", mm->opstatus.version); printf(" Capability classes: "); if (mm->opstatus.cc_acas) printf("ACAS "); if (mm->opstatus.cc_cdti) printf("CDTI "); if (mm->opstatus.cc_1090_in) printf("1090IN "); if (mm->opstatus.cc_arv) printf("ARV "); if (mm->opstatus.cc_ts) printf("TS "); if (mm->opstatus.cc_tc) printf("TC=%d ", mm->opstatus.cc_tc); if (mm->opstatus.cc_uat_in) printf("UATIN "); if (mm->opstatus.cc_poa) printf("POA "); if (mm->opstatus.cc_b2_low) printf("B2-LOW "); if (mm->opstatus.cc_lw_valid) printf("L/W=%d ", mm->opstatus.cc_lw); if (mm->opstatus.cc_antenna_offset) printf("GPS-OFFSET=%d ", mm->opstatus.cc_antenna_offset); printf("\n"); printf(" Operational modes: "); if (mm->opstatus.om_acas_ra) printf("ACASRA "); if (mm->opstatus.om_ident) printf("IDENT "); if (mm->opstatus.om_atc) printf("ATC "); if (mm->opstatus.om_saf) printf("SAF "); printf("\n"); if (mm->mesub == 1) printf(" Track/heading: %s\n", heading_type_to_string(mm->opstatus.tah)); printf(" Heading ref dir: %s\n", heading_type_to_string(mm->opstatus.hrd)); } if (mm->nav.heading_valid) printf(" Selected heading: %.1f\n", mm->nav.heading); if (mm->nav.fms_altitude_valid) printf(" FMS selected altitude: %u ft\n", mm->nav.fms_altitude); if (mm->nav.mcp_altitude_valid) printf(" MCP selected altitude: %u ft\n", mm->nav.mcp_altitude); if (mm->nav.qnh_valid) printf(" QNH: %.1f millibars\n", mm->nav.qnh); if (mm->nav.altitude_source != NAV_ALT_INVALID) { printf(" Target altitude source: "); switch (mm->nav.altitude_source) { case NAV_ALT_AIRCRAFT: printf("aircraft altitude\n"); break; case NAV_ALT_MCP: printf("MCP selected altitude\n"); break; case NAV_ALT_FMS: printf("FMS selected altitude\n"); break; default: printf("unknown\n"); } } if (mm->nav.modes_valid) { printf(" Nav modes: %s\n", nav_modes_to_string(mm->nav.modes)); } if (mm->emergency_valid) { printf(" Emergency/priority: %s\n", emergency_to_string(mm->emergency)); } printf("\n"); fflush(stdout); } // //========================================================================= // // When a new message is available, because it was decoded from the RTL device, // file, or received in the TCP input port, or any other way we can receive a // decoded message, we call this function in order to use the message. // // Basically this function passes a raw message to the upper layers for further // processing and visualization // void useModesMessage(struct modesMessage *mm) { struct aircraft *a; ++Modes.stats_current.messages_total; // Track aircraft state a = trackUpdateFromMessage(mm); // In non-interactive non-quiet mode, display messages on standard output if (!Modes.interactive && !Modes.quiet && (!Modes.show_only || mm->addr == Modes.show_only)) { displayModesMessage(mm); } // Feed output clients. // If in --net-verbatim mode, do this for all messages. // Otherwise, apply a sanity-check filter and only // forward messages when we have seen two of them. if (Modes.net) { if (Modes.net_verbatim || mm->msgtype == 32 || !a) { // Unconditionally send modesQueueOutput(mm, a); } else if (a->messages > 1) { // Suppress the first message. When we receive a second message, // emit the first two messages. if (a->messages == 2) { modesQueueOutput(&a->first_message, a); } modesQueueOutput(mm, a); } } } // // ===================== Mode S detection and decoding =================== //