src/Instrumentation/tcas.cxx

   1 // tcas.cxx -- Traffic Alert and Collision Avoidance System (TCAS) Emulation
   2 //
   3 // Written by Thorsten Brehm, started December 2010.
   4 //
   5 // Copyright (C) 2010 Thorsten Brehm - brehmt (at) gmail com
   6 //
   7 // This program is free software; you can redistribute it and/or
   8 // modify it under the terms of the GNU General Public License as
   9 // published by the Free Software Foundation; either version 2 of the
  10 // License, or (at your option) any later version.
  11 //
  12 // This program is distributed in the hope that it will be useful, but
  13 // WITHOUT ANY WARRANTY; without even the implied warranty of
  14 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15 // General Public License for more details.
  16 //
  17 // You should have received a copy of the GNU General Public License
  18 // along with this program; if not, write to the Free Software
  19 // Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301, USA.
  20 //
  21 ///////////////////////////////////////////////////////////////////////////////
  22
  23 /* References:
  24  *
  25  *  [TCASII] Introduction to TCAS II Version 7, Federal Aviation Administration, November 2000
  26  *           http://www.arinc.com/downloads/tcas/tcas.pdf
  27  *
  28  *  [EUROACAS] Eurocontrol Airborne Collision Avoidance System (ACAS),
  29  *           http://www.eurocontrol.int/msa/public/standard_page/ACAS_Startpage.html
  30  *
  31  * Glossary:
  32  *
  33  *  ALIM: Altitude Limit
  34  *
  35  *  CPA: Closest point of approach as computed from a threat's range and range rate.
  36  *
  37  *  DMOD: Distance MODification
  38  *
  39  *  Intruder: A target that has satisfied the traffic detection criteria.
  40  *
  41  *  Proximity target: Any target that is less than 6 nmi in range and within +/-1200ft
  42  *      vertically, but that does not meet the intruder or threat criteria.
  43  *
  44  *  RA: Resolution advisory. An indication given by TCAS II to a flight crew that a
  45  *      vertical maneuver should, or in some cases should not, be performed to attain or
  46  *      maintain safe separation from a threat.
  47  *
  48  *  SL: Sensitivity Level. A value used in defining the size of the protected volume
  49  *      around the own aircraft.
  50  *
  51  *  TA: Traffic Advisory. An indication given by TCAS to the pilot when an aircraft has
  52  *      entered, or is projected to enter, the protected volume around the own aircraft.
  53  *
  54  *  Tau: Approximation of the time, in seconds, to CPA or to the aircraft being at the
  55  *       same altitude.
  56  *
  57  *  TCAS: Traffic alert and Collision Avoidance System
  58  */
  59
  60 /* Module properties:
  61  *
  62  *   serviceable             enable/disable TCAS processing
  63  *
  64  *   voice/file-prefix       path (and optional prefix) for sound sample files
  65  *                           (only evaluated at start-up)
  66  *
  67  *   inputs/mode             TCAS mode selection: 0=off,1=standby,2=TA only,3=auto(TA/RA)
  68  *   inputs/self-test        trigger self-test sequence
  69  *
  70  *   outputs/traffic-alert   intruder detected (true=TA-threat is active, includes RA-threats)
  71  *   outputs/advisory-alert  resolution advisory is issued (true=advisory is valid)
  72  *   outputs/vertical-speed  vertical speed required by advisory (+/-2000/1500/500/0)
  73  *
  74  *   speaker/max-dist        Max. distance where speaker is heard
  75  *   speaker/reference-dist  Distance to pilot
  76  *   speaker/volume          Volume at reference distance
  77  *
  78  *   debug/threat-trigger    trigger debugging test (in debug mode only)
  79  *   debug/threat-RA         debugging RA value (in debug mode only)
  80  *   debug/threat-level      debugging threat level (in debug mode only)
  81  */
  82
  83 #ifdef _MSC_VER
  84 #  pragma warning( disable: 4355 )
  85 #endif
  86
  87 #ifdef HAVE_CONFIG_H
  88 #  include <config.h>
  89 #endif
  90
  91 #include <stdio.h>
  92 #include <string.h>
  93 #include <assert.h>
  94 #include <math.h>
  95
  96 #include <string>
  97 #include <sstream>
  98
  99 #include <simgear/constants.h>
 100 #include <simgear/sg_inlines.h>
 101 #include <simgear/debug/logstream.hxx>
 102 #include <simgear/math/sg_geodesy.hxx>
 103 #include <simgear/sound/soundmgr_openal.hxx>
 104 #include <simgear/structure/exception.hxx>
 105
 106 using std::string;
 107
 108 #if defined( HAVE_VERSION_H ) && HAVE_VERSION_H
 109 #  include <Include/version.h>
 110 #else
 111 #  include <Include/no_version.h>
 112 #endif
 113
 114 #include <Main/fg_props.hxx>
 115 #include <Main/globals.hxx>
 116 #include "instrument_mgr.hxx"
 117 #include "tcas.hxx"
 118
 119 ///////////////////////////////////////////////////////////////////////////////
 120 // debug switches /////////////////////////////////////////////////////////////
 121 ///////////////////////////////////////////////////////////////////////////////
 122 //#define FEATURE_TCAS_DEBUG_ANNUNCIATOR
 123 //#define FEATURE_TCAS_DEBUG_COORDINATOR
 124 //#define FEATURE_TCAS_DEBUG_THREAT_DETECTOR
 125 //#define FEATURE_TCAS_DEBUG_TRACKER
 126 //#define FEATURE_TCAS_DEBUG_ADV_GENERATOR
 127 //#define FEATURE_TCAS_DEBUG_PROPERTIES
 128
 129 ///////////////////////////////////////////////////////////////////////////////
 130 // constants //////////////////////////////////////////////////////////////////
 131 ///////////////////////////////////////////////////////////////////////////////
 132
 133 /** Sensitivity Level Definition and Alarm Thresholds (TCASII, Version 7)
 134  *  Max Own        |    |TA-level                |RA-level
 135  *  Altitude(ft)   | SL |Tau(s),DMOD(nm),ALIM(ft)|Tau(s),DMOD(nm),ALIM(ft) */
 136 const TCAS::SensitivityLevel
 137 TCAS::ThreatDetector::sensitivityLevels[] = {
 138    { 1000,           2,  {20,   0.30,     850},  {0,    0,        0  }},
 139    { 2350,           3,  {25,   0.33,     850},  {15,   0.20,     300}},
 140    { 5000,           4,  {30,   0.48,     850},  {20,   0.35,     300}},
 141    {10000,           5,  {40,   0.75,     850},  {25,   0.55,     350}},
 142    {20000,           6,  {45,   1.00,     850},  {30,   0.80,     400}},
 143    {42000,           7,  {48,   1.30,     850},  {35,   1.10,     600}},
 144    {0,               8,  {48,   1.30,    1200},  {35,   1.10,     700}}
 145 };
 146
 147 ///////////////////////////////////////////////////////////////////////////////
 148 // helpers ////////////////////////////////////////////////////////////////////
 149 ///////////////////////////////////////////////////////////////////////////////
 150
 151 #define ADD_VOICE(Var, Sample, SayTwice)    \
 152     { make_voice(&Var);                    \
 153       append(Var, Sample);                  \
 154       if (SayTwice) append(Var, Sample); }
 155
 156 #define AVAILABLE_RA(Options, Advisory) (Advisory == (Advisory & Options))
 157
 158 #ifdef FEATURE_TCAS_DEBUG_THREAT_DETECTOR
 159 /** calculate relative angle in between two headings */
 160 static float
 161 relAngle(float Heading1, float Heading2)
 162 {
 163     Heading1 -= Heading2;
 164
 165     while (Heading1 >= 360.0)
 166         Heading1 -= 360.0;
 167
 168     while (Heading1 < 0.0)
 169         Heading1 += 360;
 170
 171     return Heading1;
 172 }
 173 #endif
 174
 175 /** calculate range and bearing of lat2/lon2 relative to lat1/lon1 */
 176 static void
 177 calcRangeBearing(double lat1, double lon1, double lat2, double lon2,
 178                  double &rangeNm, double &bearing)
 179 {
 180     // calculate the bearing and range of the second pos from the first
 181     double az2, distanceM;
 182     geo_inverse_wgs_84(lat1, lon1, lat2, lon2, &bearing, &az2, &distanceM);
 183     rangeNm = distanceM * SG_METER_TO_NM;
 184 }
 185
 186 ///////////////////////////////////////////////////////////////////////////////
 187 // VoicePlayer ////////////////////////////////////////////////////////////////
 188 ///////////////////////////////////////////////////////////////////////////////
 189
 190 void
 191 TCAS::VoicePlayer::init(void)
 192 {
 193     FGVoicePlayer::init();
 194
 195     ADD_VOICE(Voices.pTrafficTraffic, "traffic",                 true);
 196     ADD_VOICE(Voices.pClear,          "clear",                   false);
 197     ADD_VOICE(Voices.pClimb,          "climb",                   true);
 198     ADD_VOICE(Voices.pClimbNow,       "climb_now",               true);
 199     ADD_VOICE(Voices.pClimbCrossing,  "climb_crossing",          true);
 200     ADD_VOICE(Voices.pClimbIncrease,  "increase_climb",          false);
 201     ADD_VOICE(Voices.pDescend,        "descend",                 true);
 202     ADD_VOICE(Voices.pDescendNow,     "descend_now",             true);
 203     ADD_VOICE(Voices.pDescendCrossing,"descend_crossing",        true);
 204     ADD_VOICE(Voices.pDescendIncrease,"increase_descent",        false);
 205     ADD_VOICE(Voices.pAdjustVSpeed,   "adjust_vertical_speed",   false);
 206     ADD_VOICE(Voices.pMaintVSpeed,    "maintain_vertical_speed", false);
 207     ADD_VOICE(Voices.pMonitorVSpeed,  "monitor_vertical_speed",  false);
 208     ADD_VOICE(Voices.pLevelOff,       "level_off",               false);
 209     ADD_VOICE(Voices.pTestOk,         "test_ok",                 false);
 210     ADD_VOICE(Voices.pTestFail,       "test_fail",               false);
 211
 212     speaker.update_configuration();
 213 }
 214
 215 /////////////////////////////////////////////////////////////////////////////
 216 // TCAS::Annunciator ////////////////////////////////////////////////////////
 217 /////////////////////////////////////////////////////////////////////////////
 218
 219 TCAS::Annunciator::Annunciator(TCAS* _tcas) :
 220     tcas(_tcas),
 221     pLastVoice(NULL),
 222     voicePlayer(_tcas)
 223 {
 224     clear();
 225 }
 226
 227 void TCAS::Annunciator::clear(void)
 228 {
 229     previous.threatLevel = ThreatNone;
 230     previous.RA          = AdvisoryClear;
 231     previous.RAOption    = OptionNone;
 232     pLastVoice = NULL;
 233 }
 234
 235 void
 236 TCAS::Annunciator::bind(SGPropertyNode* node)
 237 {
 238     voicePlayer.bind(node, "Sounds/tcas/female/");
 239 }
 240
 241 void
 242 TCAS::Annunciator::init(void)
 243 {
 244     //TODO link to GPWS module/audio-on signal must be configurable
 245     nodeGpwsAlertOn = fgGetNode("/instrumentation/mk-viii/outputs/discretes/audio-on", true);
 246     voicePlayer.init();
 247 }
 248
 249 void
 250 TCAS::Annunciator::update(void)
 251 {
 252     voicePlayer.update();
 253
 254     /* [TCASII]: "The priority scheme gives ground proximity warning systems (GPWS)
 255      *   a higher annunciation priority than a TCAS alert. TCAS aural annunciation will
 256      *   be inhibited during the time that a GPWS alert is active." */
 257     if (nodeGpwsAlertOn->getBoolValue())
 258         voicePlayer.pause();
 259     else
 260         voicePlayer.resume();
 261 }
 262
 263 /** Trigger voice sample for current alert. */
 264 void
 265 TCAS::Annunciator::trigger(const ResolutionAdvisory& current, bool revertedRA)
 266 {
 267     int RA = current.RA;
 268     int RAOption = current.RAOption;
 269
 270     if (RA == AdvisoryClear)
 271     {
 272         if (previous.RA != AdvisoryClear)
 273         {
 274             voicePlayer.play(voicePlayer.Voices.pClear, VoicePlayer::PLAY_NOW);
 275             previous = current;
 276         }
 277         pLastVoice = NULL;
 278         return;
 279     }
 280
 281     if ((previous.RA == AdvisoryClear)||
 282         (tcas->tracker.newTraffic()))
 283     {
 284         voicePlayer.play(voicePlayer.Voices.pTrafficTraffic, VoicePlayer::PLAY_NOW);
 285     }
 286
 287     // pick voice sample
 288     VoicePlayer::Voice* pVoice = NULL;
 289     switch(RA)
 290     {
 291         case AdvisoryClimb:
 292             if (revertedRA)
 293                 pVoice = voicePlayer.Voices.pClimbNow;
 294             else
 295             if (AVAILABLE_RA(RAOption, OptionIncreaseClimb))
 296                 pVoice = voicePlayer.Voices.pClimbIncrease;
 297             else
 298             if (AVAILABLE_RA(RAOption, OptionCrossingClimb))
 299                 pVoice = voicePlayer.Voices.pClimbCrossing;
 300             else
 301                 pVoice = voicePlayer.Voices.pClimb;
 302             break;
 303
 304         case AdvisoryDescend:
 305             if (revertedRA)
 306                 pVoice = voicePlayer.Voices.pDescendNow;
 307             else
 308             if (AVAILABLE_RA(RAOption, OptionIncreaseDescend))
 309                 pVoice = voicePlayer.Voices.pDescendIncrease;
 310             else
 311             if (AVAILABLE_RA(RAOption, OptionCrossingDescent))
 312                 pVoice = voicePlayer.Voices.pDescendCrossing;
 313             else
 314                 pVoice = voicePlayer.Voices.pDescend;
 315             break;
 316
 317         case AdvisoryAdjustVSpeed:
 318             pVoice = voicePlayer.Voices.pAdjustVSpeed;
 319             break;
 320
 321         case AdvisoryMaintVSpeed:
 322             pVoice = voicePlayer.Voices.pMaintVSpeed;
 323             break;
 324
 325         case AdvisoryMonitorVSpeed:
 326             pVoice = voicePlayer.Voices.pMonitorVSpeed;
 327             break;
 328
 329         case AdvisoryLevelOff:
 330             pVoice = voicePlayer.Voices.pLevelOff;
 331             break;
 332
 333         case AdvisoryIntrusion:
 334             break;
 335
 336         default:
 337             RA = AdvisoryIntrusion;
 338             break;
 339     }
 340
 341     previous = current;
 342
 343     if ((pLastVoice == pVoice)&&
 344         (!tcas->tracker.newTraffic()))
 345     {
 346         // don't repeat annunciation
 347         return;
 348     }
 349     pLastVoice = pVoice;
 350     if (pVoice)
 351         voicePlayer.play(pVoice);
 352
 353 #ifdef FEATURE_TCAS_DEBUG_ANNUNCIATOR
 354     cout << "Annunciating TCAS RA " << RA << endl;
 355 #endif
 356 }
 357
 358 void
 359 TCAS::Annunciator::test(bool testOk)
 360 {
 361     if (testOk)
 362         voicePlayer.play(voicePlayer.Voices.pTestOk);
 363     else
 364         voicePlayer.play(voicePlayer.Voices.pTestFail);
 365 }
 366
 367 /////////////////////////////////////////////////////////////////////////////
 368 // TCAS::AdvisoryCoordinator ////////////////////////////////////////////////
 369 /////////////////////////////////////////////////////////////////////////////
 370
 371 TCAS::AdvisoryCoordinator::AdvisoryCoordinator(TCAS* _tcas) :
 372   tcas(_tcas),
 373   lastTATime(0)
 374 {
 375     init();
 376 }
 377
 378 void
 379 TCAS::AdvisoryCoordinator::init(void)
 380 {
 381     clear();
 382     previous = current;
 383 }
 384
 385 void
 386 TCAS::AdvisoryCoordinator::bind(SGPropertyNode* node)
 387 {
 388     nodeTAWarning = node->getNode("outputs/traffic-alert", true);
 389     nodeTAWarning->setBoolValue(false);
 390 }
 391
 392 void
 393 TCAS::AdvisoryCoordinator::clear(void)
 394 {
 395     current.threatLevel = ThreatNone;
 396     current.RA          = AdvisoryClear;
 397     current.RAOption    = OptionNone;
 398 }
 399
 400 /** Add all suitable resolution advisories for a single threat. */
 401 void
 402 TCAS::AdvisoryCoordinator::add(const ResolutionAdvisory& newAdvisory)
 403 {
 404     if ((newAdvisory.RA == AdvisoryClear)||
 405         (newAdvisory.threatLevel < current.threatLevel))
 406         return;
 407
 408     if (current.threatLevel == newAdvisory.threatLevel)
 409     {
 410         // combine with other advisories so far
 411         current.RA &= newAdvisory.RA;
 412         // remember any advisory modifier
 413         current.RAOption |= newAdvisory.RAOption;
 414     }
 415     else
 416     {
 417         current = newAdvisory;
 418     }
 419 }
 420
 421 /** Pick and trigger suitable resolution advisory. */
 422 void
 423 TCAS::AdvisoryCoordinator::update(int mode)
 424 {
 425     bool revertedRA = false; // has advisory changed?
 426     double currentTime = globals->get_sim_time_sec();
 427
 428     if (current.RA == AdvisoryClear)
 429     {
 430         // filter: wait 5 seconds after last TA/RA before announcing TA clearance
 431         if ((previous.RA != AdvisoryClear)&&
 432              (currentTime - lastTATime < 5.0))
 433             return;
 434     }
 435     else
 436     {
 437         // intruder detected
 438
 439 #ifdef FEATURE_TCAS_DEBUG_COORDINATOR
 440         cout << "TCAS::Annunciator::update: previous: " << previous.RA << ", new: " << current.RA << endl;
 441 #endif
 442
 443         lastTATime = currentTime;
 444         if ((previous.RA == AdvisoryClear)||
 445             (previous.RA == AdvisoryIntrusion)||
 446             ((current.RA & previous.RA) != previous.RA))
 447         {
 448             // no RA yet, or we can't keep previous RA: pick one - in order of priority
 449
 450             if (AVAILABLE_RA(current.RA, AdvisoryMonitorVSpeed))
 451             {
 452                 // prio 1: monitor vertical speed only
 453                 current.RA = AdvisoryMonitorVSpeed;
 454             }
 455             else
 456             if (AVAILABLE_RA(current.RA, AdvisoryMaintVSpeed))
 457             {
 458                 // prio 2: maintain vertical speed
 459                 current.RA = AdvisoryMaintVSpeed;
 460             }
 461             else
 462             if (AVAILABLE_RA(current.RA, AdvisoryAdjustVSpeed))
 463             {
 464                 // prio 3: adjust vertical speed (TCAS II 7.0 only)
 465                 current.RA = AdvisoryAdjustVSpeed;
 466             }
 467             else
 468             if (AVAILABLE_RA(current.RA, AdvisoryLevelOff))
 469             {
 470                 // prio 3: adjust vertical speed (TCAS II 7.1 only, [EUROACAS]: CP115)
 471                 current.RA = AdvisoryLevelOff;
 472             }
 473             else
 474             if (AVAILABLE_RA(current.RA, AdvisoryClimb))
 475             {
 476                 // prio 4: climb
 477                 current.RA = AdvisoryClimb;
 478             }
 479             else
 480             if (AVAILABLE_RA(current.RA, AdvisoryDescend))
 481             {
 482                 // prio 5: descend
 483                 current.RA = AdvisoryDescend;
 484             }
 485             else
 486             {
 487                 // no RA, issue a TA only
 488                 current.RA = AdvisoryIntrusion;
 489             }
 490
 491             // check if earlier advisory was reverted
 492             revertedRA = ((previous.RA != current.RA)&&
 493                           (previous.RA != 0)&&
 494                           (previous.RA != AdvisoryIntrusion));
 495         }
 496         else
 497         {
 498             // keep earlier RA
 499             current.RA = previous.RA;
 500         }
 501     }
 502
 503     /* [TCASII]: "Aural annunciations are inhibited below 500+/-100 feet AGL." */
 504     if ((tcas->threatDetector.getRadarAlt() > 500)&&
 505         (mode >= SwitchTaOnly))
 506         tcas->annunciator.trigger(current, revertedRA);
 507     else
 508     if (current.RA == AdvisoryClear)
 509     {
 510         /* explicitly clear traffic alert (since aural annunciation disabled) */
 511         tcas->annunciator.clear();
 512     }
 513
 514     previous = current;
 515
 516     /* [TCASII] "[..] also performs the function of setting flags that control the displays.
 517      *   The traffic display, the RA display, [..] use these flags to alert the pilot to
 518      *   the presence of TAs and RAs." */
 519     nodeTAWarning->setBoolValue(current.RA != AdvisoryClear);
 520 }
 521
 522 ///////////////////////////////////////////////////////////////////////////////
 523 // TCAS::ThreatDetector ///////////////////////////////////////////////////////
 524 ///////////////////////////////////////////////////////////////////////////////
 525
 526 TCAS::ThreatDetector::ThreatDetector(TCAS* _tcas) :
 527     tcas(_tcas),
 528     checkCount(0),
 529     pAlarmThresholds(&sensitivityLevels[0])
 530 {
 531     self.radarAltFt = 0.0;
 532     unitTest();
 533 }
 534
 535 void
 536 TCAS::ThreatDetector::init(void)
 537 {
 538     nodeLat         = fgGetNode("/position/latitude-deg",          true);
 539     nodeLon         = fgGetNode("/position/longitude-deg",         true);
 540     nodePressureAlt = fgGetNode("/position/altitude-ft",           true);
 541     nodeRadarAlt    = fgGetNode("/position/altitude-agl-ft",       true);
 542     nodeHeading     = fgGetNode("/orientation/heading-deg",        true);
 543     nodeVelocity    = fgGetNode("/velocities/airspeed-kt",         true);
 544     nodeVerticalFps = fgGetNode("/velocities/vertical-speed-fps",  true);
 545
 546     tcas->advisoryGenerator.init(&self,&currentThreat);
 547 }
 548
 549 /** Update local position and threat sensitivity levels. */
 550 void
 551 TCAS::ThreatDetector::update(void)
 552 {
 553     // update local position
 554     self.lat           = nodeLat->getDoubleValue();
 555     self.lon           = nodeLon->getDoubleValue();
 556     self.pressureAltFt = nodePressureAlt->getDoubleValue();
 557     self.heading       = nodeHeading->getDoubleValue();
 558     self.velocityKt    = nodeVelocity->getDoubleValue();
 559     self.verticalFps   = nodeVerticalFps->getDoubleValue();
 560
 561     /* radar altimeter provides a lot of spikes due to uneven terrain
 562      * MK-VIII GPWS-spec requires smoothing the radar altitude with a
 563      * 10second moving average. Likely the TCAS spec requires the same.
 564      * => We use a cheap 10 second exponential average method.
 565      */
 566     const double SmoothingFactor = 0.3;
 567     self.radarAltFt = nodeRadarAlt->getDoubleValue()*SmoothingFactor +
 568             (1-SmoothingFactor)*self.radarAltFt;
 569
 570 #ifdef FEATURE_TCAS_DEBUG_THREAT_DETECTOR
 571     printf("TCAS::ThreatDetector::update: radarAlt = %f\n",self.radarAltFt);
 572     checkCount = 0;
 573 #endif
 574
 575     // determine current altitude's "Sensitivity Level Definition and Alarm Thresholds"
 576     int sl=0;
 577     for (sl=0;((self.radarAltFt > sensitivityLevels[sl].maxAltitude)&&
 578                (sensitivityLevels[sl].maxAltitude));sl++);
 579     pAlarmThresholds = &sensitivityLevels[sl];
 580     tcas->advisoryGenerator.setAlarmThresholds(pAlarmThresholds);
 581 }
 582
 583 /** Check if plane's transponder is enabled. */
 584 bool
 585 TCAS::ThreatDetector::checkTransponder(const SGPropertyNode* pModel, float velocityKt)
 586 {
 587     const string name = pModel->getName();
 588     if (name != "multiplayer" && name != "aircraft")
 589     {
 590         // assume non-MP/non-AI planes (e.g. ships) have no transponder
 591         return false;
 592     }
 593
 594     if (velocityKt < 40)
 595     {
 596         /* assume all pilots have their transponder switched off while taxiing/parking
 597          * (at low speed) */
 598         return false;
 599     }
 600
 601     if ((name == "multiplayer")&&
 602         (pModel->getBoolValue("controls/invisible")))
 603     {
 604         // ignored MP plane: pretend transponder is switched off
 605         return false;
 606     }
 607
 608     return true;
 609 }
 610
 611 /** Check if plane is a threat. */
 612 int
 613 TCAS::ThreatDetector::checkThreat(int mode, const SGPropertyNode* pModel)
 614 {
 615 #ifdef FEATURE_TCAS_DEBUG_THREAT_DETECTOR
 616     checkCount++;
 617 #endif
 618
 619     float velocityKt  = pModel->getDoubleValue("velocities/true-airspeed-kt");
 620
 621     if (!checkTransponder(pModel, velocityKt))
 622         return ThreatInvisible;
 623
 624     int threatLevel = ThreatNone;
 625     float altFt = pModel->getDoubleValue("position/altitude-ft");
 626     currentThreat.relativeAltitudeFt = altFt - self.pressureAltFt;
 627
 628     // save computation time: don't care when relative altitude is excessive
 629     if (fabs(currentThreat.relativeAltitudeFt) > 10000)
 630         return threatLevel;
 631
 632     // position data of current intruder
 633     double lat        = pModel->getDoubleValue("position/latitude-deg");
 634     double lon        = pModel->getDoubleValue("position/longitude-deg");
 635     float heading     = pModel->getDoubleValue("orientation/true-heading-deg");
 636
 637     double distanceNm, bearing;
 638     calcRangeBearing(self.lat, self.lon, lat, lon, distanceNm, bearing);
 639
 640     // save computation time: don't care for excessive distances (also captures NaNs...)
 641     if ((distanceNm > 10)||(distanceNm < 0))
 642         return threatLevel;
 643
 644     currentThreat.verticalFps = pModel->getDoubleValue("velocities/vertical-speed-fps");
 645
 646     /* Detect proximity targets
 647      * [TCASII]: "Any target that is less than 6 nmi in range and within +/-1200ft
 648      *  vertically, but that does not meet the intruder or threat criteria." */
 649     if ((distanceNm < 6)&&
 650         (fabs(currentThreat.relativeAltitudeFt) < 1200))
 651     {
 652         // at least a proximity target
 653         threatLevel = ThreatProximity;
 654     }
 655
 656     /* do not detect any threats when in standby or on ground and taxiing */
 657     if ((mode <= SwitchStandby)||
 658         ((self.radarAltFt < 360)&&(self.velocityKt < 40)))
 659     {
 660         return threatLevel;
 661     }
 662
 663     if (tcas->tracker.active())
 664     {
 665         currentThreat.callsign = pModel->getStringValue("callsign");
 666         currentThreat.isTracked = tcas->tracker.isTracked(currentThreat.callsign);
 667     }
 668     else
 669         currentThreat.isTracked = false;
 670
 671     // first stage: vertical movement
 672     checkVerticalThreat();
 673
 674     // stop processing when no vertical threat
 675     if ((!currentThreat.verticalTA)&&
 676         (!currentThreat.isTracked))
 677         return threatLevel;
 678
 679     // second stage: horizontal movement
 680     horizontalThreat(bearing, distanceNm, heading, velocityKt);
 681
 682     if (!currentThreat.isTracked)
 683     {
 684         // no horizontal threat?
 685         if (!currentThreat.horizontalTA)
 686             return threatLevel;
 687
 688         if ((currentThreat.horizontalTau < 0)||
 689             (currentThreat.verticalTau < 0))
 690         {
 691             // do not trigger new alerts when Tau is negative, but keep existing alerts
 692             int previousThreatLevel = pModel->getIntValue("tcas/threat-level", 0);
 693             if (previousThreatLevel == 0)
 694                 return threatLevel;
 695         }
 696     }
 697
 698 #ifdef FEATURE_TCAS_DEBUG_THREAT_DETECTOR
 699     cout << "#" << checkCount << ": " << pModel->getStringValue("callsign") << endl;
 700 #endif
 701
 702
 703     /* [TCASII]: "For either a TA or an RA to be issued, both the range and
 704      *    vertical criteria, in terms of tau or the fixed thresholds, must be
 705      *    satisfied only one of the criteria is satisfied, TCAS will not issue
 706      *    an advisory." */
 707     if (currentThreat.horizontalTA && currentThreat.verticalTA)
 708         threatLevel = ThreatTA;
 709     if (currentThreat.horizontalRA && currentThreat.verticalRA)
 710         threatLevel = ThreatRA;
 711
 712     if (!tcas->tracker.active())
 713         currentThreat.callsign = pModel->getStringValue("callsign");
 714
 715     tcas->tracker.add(currentThreat.callsign, threatLevel);
 716
 717     // check existing threat level
 718     if (currentThreat.isTracked)
 719     {
 720         int oldLevel = tcas->tracker.getThreatLevel(currentThreat.callsign);
 721         if (oldLevel > threatLevel)
 722             threatLevel = oldLevel;
 723     }
 724
 725     // find all resolution options for this conflict
 726     threatLevel = tcas->advisoryGenerator.resolution(mode, threatLevel, distanceNm, altFt, heading, velocityKt);
 727
 728
 729 #ifdef FEATURE_TCAS_DEBUG_THREAT_DETECTOR
 730     printf("  threat: distance: %4.1f, bearing: %4.1f, alt: %5.1f, velocity: %4.1f, heading: %4.1f, vspeed: %4.1f, "
 731            "own alt: %5.1f, own heading: %4.1f, own velocity: %4.1f, vertical tau: %3.2f"
 732            //", closing speed: %f"
 733            "\n",
 734            distanceNm, relAngle(bearing, self.heading), altFt, velocityKt, heading, currentThreat.verticalFps,
 735            self.altFt, self.heading, self.velocityKt
 736            //, currentThreat.closingSpeedKt
 737            ,currentThreat.verticalTau
 738            );
 739 #endif
 740
 741     return threatLevel;
 742 }
 743
 744 /** Check if plane is a vertical threat. */
 745 void
 746 TCAS::ThreatDetector::checkVerticalThreat(void)
 747 {
 748     // calculate relative vertical speed and altitude
 749     float dV = self.verticalFps - currentThreat.verticalFps;
 750     float dA = currentThreat.relativeAltitudeFt;
 751
 752     currentThreat.verticalTA  = false;
 753     currentThreat.verticalRA  = false;
 754     currentThreat.verticalTau = 0;
 755
 756     /* [TCASII]: "The vertical tau is equal to the altitude separation (feet)
 757      *   divided by the combined vertical speed of the two aircraft (feet/minute)
 758      *   times 60." */
 759     float tau = 0;
 760     if (fabs(dV) > 0.1)
 761         tau = dA/dV;
 762
 763     /* [TCASII]: "When the combined vertical speed of the TCAS and the intruder aircraft
 764      *    is low, TCAS will use a fixed-altitude threshold to determine whether a TA or
 765      *    an RA should be issued." */
 766     if ((fabs(dV) < 3.0)||
 767         ((tau < 0) && (tau > -5)))
 768     {
 769         /* vertical closing speed is low (below 180fpm/3fps), check
 770          * fixed altitude range. */
 771         float abs_dA = fabs(dA);
 772         if (abs_dA < pAlarmThresholds->RA.ALIM)
 773         {
 774             // continuous intrusion at RA-level
 775             currentThreat.verticalTA = true;
 776             currentThreat.verticalRA = true;
 777         }
 778         else
 779         if (abs_dA < pAlarmThresholds->TA.ALIM)
 780         {
 781             // continuous intrusion: with TA-level, but no RA-threat
 782             currentThreat.verticalTA = true;
 783         }
 784         // else: no RA/TA threat
 785     }
 786     else
 787     {
 788         if ((tau < pAlarmThresholds->TA.Tau)&&
 789             (tau >= -5))
 790         {
 791             currentThreat.verticalTA = true;
 792             currentThreat.verticalRA = (tau < pAlarmThresholds->RA.Tau);
 793         }
 794     }
 795     currentThreat.verticalTau = tau;
 796
 797 #ifdef FEATURE_TCAS_DEBUG_THREAT_DETECTOR
 798     if (currentThreat.verticalTA)
 799         printf("  vertical dV=%f (%f-%f), dA=%f\n", dV, self.verticalFps, currentThreat.verticalFps, dA);
 800 #endif
 801 }
 802
 803 /** Check if plane is a horizontal threat. */
 804 void
 805 TCAS::ThreatDetector::horizontalThreat(float bearing, float distanceNm, float heading, float velocityKt)
 806 {
 807     // calculate speed
 808     float vxKt = sin(heading*SGD_DEGREES_TO_RADIANS)*velocityKt - sin(self.heading*SGD_DEGREES_TO_RADIANS)*self.velocityKt;
 809     float vyKt = cos(heading*SGD_DEGREES_TO_RADIANS)*velocityKt - cos(self.heading*SGD_DEGREES_TO_RADIANS)*self.velocityKt;
 810
 811     // calculate horizontal closing speed
 812     float closingSpeedKt2 = vxKt*vxKt+vyKt*vyKt;
 813     float closingSpeedKt  = sqrt(closingSpeedKt2);
 814
 815     /* [TCASII]: "The range tau is equal to the slant range (nmi) divided by the closing speed
 816      *    (knots) multiplied by 3600."
 817      * => calculate allowed slant range (nmi) based on known maximum tau */
 818     float TA_rangeNm = (pAlarmThresholds->TA.Tau*closingSpeedKt)/3600;
 819     float RA_rangeNm = (pAlarmThresholds->RA.Tau*closingSpeedKt)/3600;
 820
 821     if (closingSpeedKt < 100)
 822     {
 823         /* [TCASII]: "In events where the rate of closure is very low, [..]
 824          *    an intruder aircraft can come very close in range without crossing the
 825          *    range tau boundaries [..]. To provide protection in these types of
 826          *    advisories, the range tau boundaries are modified [..] to use
 827          *    a fixed-range threshold to issue TAs and RAs in these slow closure
 828          *    encounters." */
 829         TA_rangeNm += (100.0-closingSpeedKt)*(pAlarmThresholds->TA.DMOD/100.0);
 830         RA_rangeNm += (100.0-closingSpeedKt)*(pAlarmThresholds->RA.DMOD/100.0);
 831     }
 832     if (TA_rangeNm < pAlarmThresholds->TA.DMOD)
 833         TA_rangeNm = pAlarmThresholds->TA.DMOD;
 834     if (RA_rangeNm < pAlarmThresholds->RA.DMOD)
 835         RA_rangeNm = pAlarmThresholds->RA.DMOD;
 836
 837     currentThreat.horizontalTA   = (distanceNm < TA_rangeNm);
 838     currentThreat.horizontalRA   = (distanceNm < RA_rangeNm);
 839     currentThreat.horizontalTau  = -1;
 840
 841     if ((currentThreat.horizontalRA)&&
 842         (currentThreat.verticalRA))
 843     {
 844         /* an RA will be issued. Prepare extra data for the
 845          * traffic resolution stage, i.e. calculate
 846          * exact time tau to horizontal CPA.
 847          */
 848
 849         /* relative position of intruder is
 850          *   Sx(t) = sx + vx*t
 851          *   Sy(t) = sy + vy*t
 852          * horizontal distance to intruder is r(t)
 853          *   r(t) = sqrt( Sx(t)^2 + Sy(t)^2 )
 854          * => horizontal CPA at time t=tau, where r(t) has minimum
 855          * r2(t) := r^2(t) = Sx(t)^2 + Sy(t)^2
 856          * since r(t)>0 for all t => minimum of r(t) is also minimum of r2(t)
 857          * => (d/dt) r2(t) = r2'(t) is 0 for t=tau
 858          *    r2(t) = ((Sx(t)^2 + Sy(t))^2) = c + b*t + a*t^2
 859          * => r2'(t) = b + a*2*t
 860          * at t=tau:
 861          *    r2'(tau) = 0 = b + 2*a*tau
 862          * => tau = -b/(2*a)
 863          */
 864         float sx = sin(bearing*SGD_DEGREES_TO_RADIANS)*distanceNm;
 865         float sy = cos(bearing*SGD_DEGREES_TO_RADIANS)*distanceNm;
 866         float vx = vxKt * (SG_KT_TO_MPS*SG_METER_TO_NM);
 867         float vy = vyKt * (SG_KT_TO_MPS*SG_METER_TO_NM);
 868         float a  = vx*vx + vy*vy;
 869         float b  = 2*(sx*vx + sy*vy);
 870         float tau = 0;
 871         if (a > 0.0001)
 872             tau = -b/(2*a);
 873 #ifdef FEATURE_TCAS_DEBUG_THREAT_DETECTOR
 874         printf("  Time to horizontal CPA: %4.2f\n",tau);
 875 #endif
 876         if (tau > pAlarmThresholds->RA.Tau)
 877             tau = pAlarmThresholds->RA.Tau;
 878
 879         // remember time to horizontal CPA
 880         currentThreat.horizontalTau = tau;
 881     }
 882 }
 883
 884 /** Test threat detection logic. */
 885 void
 886 TCAS::ThreatDetector::unitTest(void)
 887 {
 888     pAlarmThresholds = &sensitivityLevels[1];
 889 #if 0
 890     // vertical tests
 891     self.verticalFps = 0;
 892     self.altFt = 1000;
 893     cout << "identical altitude and vspeed " << endl;
 894     checkVerticalThreat(self.altFt, self.verticalFps);
 895     cout << "1000ft alt offset, dV=100 " << endl;
 896     checkVerticalThreat(self.altFt+1000, 100);
 897     cout << "-1000ft alt offset, dV=100 " << endl;
 898     checkVerticalThreat(self.altFt-1000, 100);
 899     cout << "3000ft alt offset, dV=10 " << endl;
 900     checkVerticalThreat(self.altFt+3000, 10);
 901     cout << "500ft alt offset, dV=100 " << endl;
 902     checkVerticalThreat(self.altFt+500, 100);
 903     cout << "500ft alt offset, dV=-100 " << endl;
 904     checkVerticalThreat(self.altFt+500, -100);
 905
 906     // horizontal tests
 907     self.heading = 0;
 908     self.velocityKt = 0;
 909     cout << "10nm behind, overtaking with 1Nm/s" << endl;
 910     horizontalThreat(-180, 10, 0, 1/(SG_KT_TO_MPS*SG_METER_TO_NM));
 911
 912     cout << "10nm ahead, departing with 1Nm/s" << endl;
 913     horizontalThreat(0, 20, 0, 1/(SG_KT_TO_MPS*SG_METER_TO_NM));
 914
 915     self.heading = 90;
 916     self.velocityKt = 1/(SG_KT_TO_MPS*SG_METER_TO_NM);
 917     cout << "10nm behind, overtaking with 1Nm/s at 90 degrees" << endl;
 918     horizontalThreat(-90, 20, 90, 2/(SG_KT_TO_MPS*SG_METER_TO_NM));
 919
 920     self.heading = 20;
 921     self.velocityKt = 1/(SG_KT_TO_MPS*SG_METER_TO_NM);
 922     cout << "10nm behind, overtaking with 1Nm/s at 20 degrees" << endl;
 923     horizontalThreat(200, 20, 20, 2/(SG_KT_TO_MPS*SG_METER_TO_NM));
 924 #endif
 925 }
 926
 927 ///////////////////////////////////////////////////////////////////////////////
 928 // TCAS::AdvisoryGenerator ////////////////////////////////////////////////////
 929 ///////////////////////////////////////////////////////////////////////////////
 930
 931 TCAS::AdvisoryGenerator::AdvisoryGenerator(TCAS* _tcas) :
 932     tcas(_tcas),
 933     pSelf(NULL),
 934     pCurrentThreat(NULL),
 935     pAlarmThresholds(NULL)
 936 {
 937 }
 938
 939 void
 940 TCAS::AdvisoryGenerator::init(const LocalInfo* _pSelf, ThreatInfo* _pCurrentThreat)
 941 {
 942     pCurrentThreat = _pCurrentThreat;
 943     pSelf = _pSelf;
 944 }
 945
 946 void
 947 TCAS::AdvisoryGenerator::setAlarmThresholds(const SensitivityLevel* _pAlarmThresholds)
 948 {
 949     pAlarmThresholds = _pAlarmThresholds;
 950 }
 951
 952 /** Calculate projected vertical separation at horizontal CPA. */
 953 float
 954 TCAS::AdvisoryGenerator::verticalSeparation(float newVerticalFps)
 955 {
 956     // calculate relative vertical speed and altitude
 957     float dV = pCurrentThreat->verticalFps - newVerticalFps;
 958     float tau = pCurrentThreat->horizontalTau;
 959     // don't use negative tau to project future separation...
 960     if (tau < 0.5)
 961         tau = 0.5;
 962     return pCurrentThreat->relativeAltitudeFt + tau * dV;
 963 }
 964
 965 /** Determine RA sense. */
 966 void
 967 TCAS::AdvisoryGenerator::determineRAsense(int& RASense, bool& isCrossing)
 968 {
 969     /* [TCASII]: "[..] a two step process is used to select the appropriate RA for the encounter
 970              *   geometry. The first step in the process is to select the RA sense, i.e., upward or downward." */
 971     RASense = 0;
 972     isCrossing = false;
 973
 974     /* [TCASII]: "Based on the range and altitude tracks of the intruder, the CAS logic models the
 975      *   intruder's flight path from its present position to CPA. The CAS logic then models upward
 976      *   and downward sense RAs for own aircraft [..] to determine which sense provides the most
 977      *   vertical separation at CPA." */
 978     float upSenseRelAltFt   = verticalSeparation(+2000/60.0);
 979     float downSenseRelAltFt = verticalSeparation(-2000/60.0);
 980     if (fabs(upSenseRelAltFt) >= fabs(downSenseRelAltFt))
 981         RASense = +1;  // upward
 982     else
 983         RASense = -1; // downward
 984
 985     /* [TCASII]: "In encounters where either of the senses results in the TCAS aircraft crossing through
 986      *   the intruder's altitude, TCAS is designed to select the nonaltitude crossing sense if the
 987      *   noncrossing sense provides the desired vertical separation, known as ALIM, at CPA." */
 988     /* [TCASII]: "If ALIM cannot be obtained in the nonaltitude crossing sense, an altitude
 989      *   crossing RA will be issued." */
 990     if ((RASense > 0)&&
 991         (pCurrentThreat->relativeAltitudeFt > 200))
 992     {
 993         // threat is above and RA is crossing
 994         if (fabs(downSenseRelAltFt) > pAlarmThresholds->TA.ALIM)
 995         {
 996             // non-crossing descend is sufficient
 997             RASense = -1;
 998         }
 999         else
1000         {
1001             // keep crossing climb RA
1002             isCrossing = true;
1003         }
1004     }
1005     else
1006     if ((RASense < 0)&&
1007         (pCurrentThreat->relativeAltitudeFt < -200))
1008     {
1009         // threat is below and RA is crossing
1010         if (fabs(upSenseRelAltFt) > pAlarmThresholds->TA.ALIM)
1011         {
1012             // non-crossing climb is sufficient
1013             RASense = 1;
1014         }
1015         else
1016         {
1017             // keep crossing descent RA
1018             isCrossing = true;
1019         }
1020     }
1021     // else: threat is at same altitude, keep optimal RA sense (non-crossing)
1022
1023     pCurrentThreat->RASense = RASense;
1024
1025 #ifdef FEATURE_TCAS_DEBUG_ADV_GENERATOR
1026         printf("  RASense: %i, crossing: %u, relAlt: %4.1f, upward separation: %4.1f, downward separation: %4.1f\n",
1027                RASense,isCrossing,
1028                pCurrentThreat->relativeAltitudeFt,
1029                upSenseRelAltFt,downSenseRelAltFt);
1030 #endif
1031 }
1032
1033 /** Determine suitable resolution advisories. */
1034 int
1035 TCAS::AdvisoryGenerator::resolution(int mode, int threatLevel, float rangeNm, float altFt,
1036                                     float heading, float velocityKt)
1037 {
1038     int RAOption = OptionNone;
1039     int RA       = AdvisoryIntrusion;
1040
1041     // RAs are disabled under certain conditions
1042     if (threatLevel == ThreatRA)
1043     {
1044         /* [TCASII]: "... less than 360 feet, TCAS considers the reporting aircraft
1045          *   to be on the ground. If TCAS determines the intruder to be on the ground, it
1046          *   inhibits the generation of advisories against this aircraft."*/
1047         if (altFt < 360)
1048             threatLevel = ThreatTA;
1049
1050         /* [EUROACAS]: "Certain RAs are inhibited at altitudes based on inputs from the radio altimeter:
1051          *   [..] (c)1000ft (+/- 100ft) and below, all RAs are inhibited;" */
1052         if (pSelf->radarAltFt < 1000)
1053             threatLevel = ThreatTA;
1054
1055         // RAs only issued in mode "Auto" (= "TA/RA" mode)
1056         if (mode != SwitchAuto)
1057             threatLevel = ThreatTA;
1058     }
1059
1060     bool isCrossing = false;
1061     int RASense = 0;
1062     // determine suitable RAs
1063     if (threatLevel == ThreatRA)
1064     {
1065         /* [TCASII]: "[..] a two step process is used to select the appropriate RA for the encounter
1066          *   geometry. The first step in the process is to select the RA sense, i.e., upward or downward." */
1067         determineRAsense(RASense, isCrossing);
1068
1069         /* second step: determine required strength */
1070         if (RASense > 0)
1071         {
1072             // upward
1073
1074             if ((pSelf->verticalFps < -1000/60.0)&&
1075                 (!isCrossing))
1076             {
1077                 // currently descending, see if reducing current descent is sufficient
1078                 float relAltFt = verticalSeparation(-500/60.0);
1079                 if (relAltFt > pAlarmThresholds->TA.ALIM)
1080                     RA |= AdvisoryAdjustVSpeed;
1081             }
1082             RA |= AdvisoryClimb;
1083             if (isCrossing)
1084                 RAOption |= OptionCrossingClimb;
1085         }
1086
1087         if (RASense < 0)
1088         {
1089             // downward
1090
1091             if ((pSelf->verticalFps > 1000/60.0)&&
1092                 (!isCrossing))
1093             {
1094                 // currently climbing, see if reducing current climb is sufficient
1095                 float relAltFt = verticalSeparation(500/60.0);
1096                 if (relAltFt < -pAlarmThresholds->TA.ALIM)
1097                     RA |= AdvisoryAdjustVSpeed;
1098             }
1099             RA |= AdvisoryDescend;
1100             if (isCrossing)
1101                 RAOption |= OptionCrossingDescent;
1102         }
1103
1104         //TODO
1105         /* [TCASII]: "When two TCAS-equipped aircraft are converging vertically with opposite rates
1106          *   and are currently well separated in altitude, TCAS will first issue a vertical speed
1107          *   limit (Negative) RA to reinforce the pilots' likely intention to level off at adjacent
1108          *   flight levels." */
1109
1110         //TODO
1111         /* [TCASII]: "[..] if the CAS logic determines that the response to a Positive RA has provided
1112          *   ALIM feet of vertical separation before CPA, the initial RA will be weakened to either a
1113          *   Do Not Descend RA (after an initial Climb RA) or a Do Not Climb RA (after an initial
1114          *   Descend RA)." */
1115
1116         //TODO
1117         /* [TCASII]: "TCAS is designed to inhibit Increase Descent RAs below 1450 feet AGL; */
1118
1119         /* [TCASII]: "Descend RAs below 1100 feet AGL;" (inhibited) */
1120         if (pSelf->radarAltFt < 1100)
1121         {
1122             RA &= ~AdvisoryDescend;
1123             //TODO Support "Do not descend" RA
1124             RA |= AdvisoryIntrusion;
1125         }
1126     }
1127
1128 #ifdef FEATURE_TCAS_DEBUG_ADV_GENERATOR
1129     cout << "  resolution advisory: " << RA << endl;
1130 #endif
1131
1132     ResolutionAdvisory newAdvisory;
1133     newAdvisory.RAOption    = RAOption;
1134     newAdvisory.RA          = RA;
1135     newAdvisory.threatLevel = threatLevel;
1136     tcas->advisoryCoordinator.add(newAdvisory);
1137
1138     return threatLevel;
1139 }
1140
1141 ///////////////////////////////////////////////////////////////////////////////
1142 // TCAS ///////////////////////////////////////////////////////////////////////
1143 ///////////////////////////////////////////////////////////////////////////////
1144
1145 TCAS::TCAS(SGPropertyNode* pNode) :
1146     name("tcas"),
1147     num(0),
1148     nextUpdateTime(0),
1149     selfTestStep(0),
1150     properties_handler(this),
1151     threatDetector(this),
1152     tracker(this),
1153     advisoryCoordinator(this),
1154     advisoryGenerator(this),
1155     annunciator(this)
1156 {
1157     for (int i = 0; i < pNode->nChildren(); ++i)
1158     {
1159         SGPropertyNode* pChild = pNode->getChild(i);
1160         string cname = pChild->getName();
1161         string cval = pChild->getStringValue();
1162
1163         if (cname == "name")
1164             name = cval;
1165         else if (cname == "number")
1166             num = pChild->getIntValue();
1167         else
1168         {
1169             SG_LOG(SG_INSTR, SG_WARN, "Error in TCAS config logic");
1170             if (name.length())
1171                 SG_LOG(SG_INSTR, SG_WARN, "Section = " << name);
1172         }
1173     }
1174 }
1175
1176 void
1177 TCAS::init(void)
1178 {
1179     annunciator.init();
1180     advisoryCoordinator.init();
1181     threatDetector.init();
1182 }
1183
1184 void
1185 TCAS::bind(void)
1186 {
1187     SGPropertyNode* node = fgGetNode(("/instrumentation/" + name).c_str(), num, true);
1188
1189     nodeServiceable  = node->getNode("serviceable", true);
1190
1191     // TCAS mode selection (0=off, 1=standby, 2=TA only, 3=auto(TA/RA) )
1192     nodeModeSwitch   = node->getNode("inputs/mode", true);
1193     // self-test button
1194     nodeSelfTest     = node->getNode("inputs/self-test", true);
1195     // default value
1196     nodeSelfTest->setBoolValue(false);
1197
1198 #ifdef FEATURE_TCAS_DEBUG_PROPERTIES
1199     SGPropertyNode* nodeDebug = node->getNode("debug", true);
1200     // debug triggers
1201     nodeDebugTrigger = nodeDebug->getNode("threat-trigger", true);
1202     nodeDebugRA      = nodeDebug->getNode("threat-RA",      true);
1203     nodeDebugThreat  = nodeDebug->getNode("threat-level",   true);
1204     // default values
1205     nodeDebugTrigger->setBoolValue(false);
1206     nodeDebugRA->setIntValue(3);
1207     nodeDebugThreat->setIntValue(1);
1208 #endif
1209
1210     annunciator.bind(node);
1211     advisoryCoordinator.bind(node);
1212 }
1213
1214 void
1215 TCAS::unbind(void)
1216 {
1217     properties_handler.unbind();
1218 }
1219
1220 /** Monitor traffic for safety threats. */
1221 void
1222 TCAS::update(double dt)
1223 {
1224     if (!nodeServiceable->getBoolValue())
1225         return;
1226     int mode = nodeModeSwitch->getIntValue();
1227     if (mode == SwitchOff)
1228         return;
1229
1230     nextUpdateTime -= dt;
1231     if (nextUpdateTime <= 0.0 )
1232     {
1233         nextUpdateTime = 1.0;
1234
1235         // remove obsolete targets
1236         tracker.update();
1237
1238         // get aircrafts current position/speed/heading
1239         threatDetector.update();
1240
1241         // clear old threats
1242         advisoryCoordinator.clear();
1243
1244         if (nodeSelfTest->getBoolValue())
1245         {
1246             if (threatDetector.getVelocityKt() >= 40)
1247             {
1248                 // disable self-test when plane moves above taxiing speed
1249                 nodeSelfTest->setBoolValue(false);
1250                 selfTestStep = 0;
1251             }
1252             else
1253             {
1254                 selfTest();
1255                 // speed-up self test
1256                 nextUpdateTime = 0;
1257                 // no further TCAS processing during self-test
1258                 return;
1259             }
1260         }
1261
1262 #ifdef FEATURE_TCAS_DEBUG_PROPERTIES
1263         if (nodeDebugTrigger->getBoolValue())
1264         {
1265             // debugging test
1266             ResolutionAdvisory debugAdvisory;
1267             debugAdvisory.RAOption    = OptionNone;
1268             debugAdvisory.RA          = nodeDebugRA->getIntValue();
1269             debugAdvisory.threatLevel = nodeDebugThreat->getIntValue();
1270             advisoryCoordinator.add(debugAdvisory);
1271         }
1272         else
1273 #endif
1274         {
1275             SGPropertyNode* pAi = fgGetNode("/ai/models", true);
1276
1277             // check all aircraft
1278             for (int i = pAi->nChildren() - 1; i >= -1; i--)
1279             {
1280                 SGPropertyNode* pModel = pAi->getChild(i);
1281                 if ((pModel)&&(pModel->nChildren()))
1282                 {
1283                     int threatLevel = threatDetector.checkThreat(mode, pModel);
1284                     /* expose aircraft threat-level (to be used by other instruments,
1285                      * i.e. TCAS display) */
1286                     if (threatLevel==ThreatRA)
1287                         pModel->setIntValue("tcas/ra-sense", -threatDetector.getRASense());
1288                     pModel->setIntValue("tcas/threat-level", threatLevel);
1289                 }
1290             }
1291         }
1292         advisoryCoordinator.update(mode);
1293     }
1294     annunciator.update();
1295 }
1296
1297 /** Run a single self-test iteration. */
1298 void
1299 TCAS::selfTest(void)
1300 {
1301     annunciator.update();
1302     if (annunciator.isPlaying())
1303     {
1304         return;
1305     }
1306
1307     ResolutionAdvisory newAdvisory;
1308     newAdvisory.threatLevel = ThreatRA;
1309     newAdvisory.RA          = AdvisoryClear;
1310     newAdvisory.RAOption    = OptionNone;
1311     // TCAS audio is disabled below 500ft AGL
1312     threatDetector.setRadarAlt(501);
1313
1314     // trigger various advisories
1315     switch(selfTestStep)
1316     {
1317         case 0:
1318             newAdvisory.RA = AdvisoryIntrusion;
1319             newAdvisory.threatLevel = ThreatTA;
1320             break;
1321         case 1:
1322             newAdvisory.RA = AdvisoryClimb;
1323             break;
1324         case 2:
1325             newAdvisory.RA = AdvisoryClimb;
1326             newAdvisory.RAOption = OptionIncreaseClimb;
1327             break;
1328         case 3:
1329             newAdvisory.RA = AdvisoryClimb;
1330             newAdvisory.RAOption = OptionCrossingClimb;
1331             break;
1332         case 4:
1333             newAdvisory.RA = AdvisoryDescend;
1334             break;
1335         case 5:
1336             newAdvisory.RA = AdvisoryDescend;
1337             newAdvisory.RAOption = OptionIncreaseDescend;
1338             break;
1339         case 6:
1340             newAdvisory.RA = AdvisoryDescend;
1341             newAdvisory.RAOption = OptionCrossingDescent;
1342             break;
1343         case 7:
1344             newAdvisory.RA = AdvisoryAdjustVSpeed;
1345             break;
1346         case 8:
1347             newAdvisory.RA = AdvisoryMaintVSpeed;
1348             break;
1349         case 9:
1350             newAdvisory.RA = AdvisoryMonitorVSpeed;
1351             break;
1352         case 10:
1353             newAdvisory.threatLevel = ThreatNone;
1354             newAdvisory.RA = AdvisoryClear;
1355             break;
1356         case 11:
1357             annunciator.test(true);
1358             selfTestStep+=2;
1359             return;
1360         default:
1361             nodeSelfTest->setBoolValue(false);
1362             selfTestStep = 0;
1363             return;
1364     }
1365
1366     advisoryCoordinator.add(newAdvisory);
1367     advisoryCoordinator.update(SwitchAuto);
1368
1369     selfTestStep++;
1370 }
1371
1372 ///////////////////////////////////////////////////////////////////////////////
1373 // TCAS::Tracker //////////////////////////////////////////////////////////////
1374 ///////////////////////////////////////////////////////////////////////////////
1375
1376 TCAS::Tracker::Tracker(TCAS* _tcas) :
1377     tcas(_tcas),
1378     currentTime(0),
1379     haveTargets(false),
1380     newTargets(false)
1381 {
1382     targets.clear();
1383 }
1384
1385 void
1386 TCAS::Tracker::update(void)
1387 {
1388     currentTime = globals->get_sim_time_sec();
1389     newTargets = false;
1390
1391     if (haveTargets)
1392     {
1393         // remove outdated targets
1394         TrackerTargets::iterator it = targets.begin();
1395         while (it != targets.end())
1396         {
1397             TrackerTarget* pTarget = it->second;
1398             if (currentTime - pTarget->TAtimestamp > 10.0)
1399             {
1400                 TrackerTargets::iterator temp = it;
1401                 ++it;
1402 #ifdef FEATURE_TCAS_DEBUG_TRACKER
1403                 printf("target %s no longer a TA threat.\n",temp->first.c_str());
1404 #endif
1405                 targets.erase(temp->first);
1406                 delete pTarget;
1407                 pTarget = NULL;
1408             }
1409             else
1410             {
1411                 if ((pTarget->threatLevel == ThreatRA)&&
1412                     (currentTime - pTarget->RAtimestamp > 7.0))
1413                 {
1414                     pTarget->threatLevel = ThreatTA;
1415 #ifdef FEATURE_TCAS_DEBUG_TRACKER
1416                     printf("target %s no longer an RA threat.\n",it->first.c_str());
1417 #endif
1418                 }
1419                 ++it;
1420             }
1421         }
1422         haveTargets = !targets.empty();
1423     }
1424 }
1425
1426 void
1427 TCAS::Tracker::add(const string callsign, int detectedLevel)
1428 {
1429     TrackerTarget* pTarget = NULL;
1430     if (haveTargets)
1431     {
1432         TrackerTargets::iterator it = targets.find(callsign);
1433         if (it != targets.end())
1434         {
1435             pTarget = it->second;
1436         }
1437     }
1438
1439     if (!pTarget)
1440     {
1441         pTarget = new TrackerTarget();
1442         pTarget->TAtimestamp = 0;
1443         pTarget->RAtimestamp = 0;
1444         pTarget->threatLevel = 0;
1445         newTargets = true;
1446         targets[callsign] = pTarget;
1447 #ifdef FEATURE_TCAS_DEBUG_TRACKER
1448         printf("new target: %s, level: %i\n",callsign.c_str(),detectedLevel);
1449 #endif
1450     }
1451
1452     if (detectedLevel > pTarget->threatLevel)
1453         pTarget->threatLevel = detectedLevel;
1454
1455     if (detectedLevel >= ThreatTA)
1456         pTarget->TAtimestamp = currentTime;
1457
1458     if (detectedLevel >= ThreatRA)
1459         pTarget->RAtimestamp = currentTime;
1460
1461     haveTargets = true;
1462 }
1463
1464 bool
1465 TCAS::Tracker::_isTracked(string callsign)
1466 {
1467     return targets.find(callsign) != targets.end();
1468 }
1469
1470 int
1471 TCAS::Tracker::getThreatLevel(string callsign)
1472 {
1473     TrackerTargets::iterator it = targets.find(callsign);
1474     if (it != targets.end())
1475         return it->second->threatLevel;
1476     else
1477         return 0;
1478 }