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/sound/sample_group.hxx>
 105 #include <simgear/structure/exception.hxx>
 106
 107 using std::string;
 108
 109 #if defined( HAVE_VERSION_H ) && HAVE_VERSION_H
 110 #  include <Include/version.h>
 111 #else
 112 #  include <Include/no_version.h>
 113 #endif
 114
 115 #include <Main/fg_props.hxx>
 116 #include <Main/globals.hxx>
 117 #include "instrument_mgr.hxx"
 118 #include "tcas.hxx"
 119
 120 ///////////////////////////////////////////////////////////////////////////////
 121 // debug switches /////////////////////////////////////////////////////////////
 122 ///////////////////////////////////////////////////////////////////////////////
 123 //#define FEATURE_TCAS_DEBUG_ANNUNCIATOR
 124 //#define FEATURE_TCAS_DEBUG_COORDINATOR
 125 //#define FEATURE_TCAS_DEBUG_THREAT_DETECTOR
 126 //#define FEATURE_TCAS_DEBUG_TRACKER
 127 //#define FEATURE_TCAS_DEBUG_ADV_GENERATOR
 128 //#define FEATURE_TCAS_DEBUG_PROPERTIES
 129
 130 ///////////////////////////////////////////////////////////////////////////////
 131 // constants //////////////////////////////////////////////////////////////////
 132 ///////////////////////////////////////////////////////////////////////////////
 133
 134 /** Sensitivity Level Definition and Alarm Thresholds (TCASII, Version 7)
 135  *  Max Own        |    |TA-level                |RA-level
 136  *  Altitude(ft)   | SL |Tau(s),DMOD(nm),ALIM(ft)|Tau(s),DMOD(nm),ALIM(ft) */
 137 const TCAS::SensitivityLevel
 138 TCAS::ThreatDetector::sensitivityLevels[] = {
 139    { 1000,           2,  {20,   0.30,     850},  {0,    0,        0  }},
 140    { 2350,           3,  {25,   0.33,     850},  {15,   0.20,     300}},
 141    { 5000,           4,  {30,   0.48,     850},  {20,   0.35,     300}},
 142    {10000,           5,  {40,   0.75,     850},  {25,   0.55,     350}},
 143    {20000,           6,  {45,   1.00,     850},  {30,   0.80,     400}},
 144    {42000,           7,  {48,   1.30,     850},  {35,   1.10,     600}},
 145    {0,               8,  {48,   1.30,    1200},  {35,   1.10,     700}}
 146 };
 147
 148 ///////////////////////////////////////////////////////////////////////////////
 149 // helpers ////////////////////////////////////////////////////////////////////
 150 ///////////////////////////////////////////////////////////////////////////////
 151
 152 #define ADD_VOICE(Var, Sample, SayTwice)    \
 153     { make_voice(&Var);                    \
 154       append(Var, Sample);                  \
 155       if (SayTwice) append(Var, Sample); }
 156
 157 #define AVAILABLE_RA(Options, Advisory) (Advisory == (Advisory & Options))
 158
 159 #ifdef FEATURE_TCAS_DEBUG_THREAT_DETECTOR
 160 /** calculate relative angle in between two headings */
 161 static float
 162 relAngle(float Heading1, float Heading2)
 163 {
 164     Heading1 -= Heading2;
 165
 166     while (Heading1 >= 360.0)
 167         Heading1 -= 360.0;
 168
 169     while (Heading1 < 0.0)
 170         Heading1 += 360;
 171
 172     return Heading1;
 173 }
 174 #endif
 175
 176 /** calculate range and bearing of lat2/lon2 relative to lat1/lon1 */
 177 static void
 178 calcRangeBearing(double lat1, double lon1, double lat2, double lon2,
 179                  double &rangeNm, double &bearing)
 180 {
 181     // calculate the bearing and range of the second pos from the first
 182     double az2, distanceM;
 183     geo_inverse_wgs_84(lat1, lon1, lat2, lon2, &bearing, &az2, &distanceM);
 184     rangeNm = distanceM * SG_METER_TO_NM;
 185 }
 186
 187 ///////////////////////////////////////////////////////////////////////////////
 188 // VoicePlayer ////////////////////////////////////////////////////////////////
 189 ///////////////////////////////////////////////////////////////////////////////
 190
 191 void
 192 TCAS::VoicePlayer::init(void)
 193 {
 194     FGVoicePlayer::init();
 195
 196     ADD_VOICE(Voices.pTrafficTraffic, "traffic",                 true);
 197     ADD_VOICE(Voices.pClear,          "clear",                   false);
 198     ADD_VOICE(Voices.pClimb,          "climb",                   true);
 199     ADD_VOICE(Voices.pClimbNow,       "climb_now",               true);
 200     ADD_VOICE(Voices.pClimbCrossing,  "climb_crossing",          true);
 201     ADD_VOICE(Voices.pClimbIncrease,  "increase_climb",          false);
 202     ADD_VOICE(Voices.pDescend,        "descend",                 true);
 203     ADD_VOICE(Voices.pDescendNow,     "descend_now",             true);
 204     ADD_VOICE(Voices.pDescendCrossing,"descend_crossing",        true);
 205     ADD_VOICE(Voices.pDescendIncrease,"increase_descent",        false);
 206     ADD_VOICE(Voices.pAdjustVSpeed,   "adjust_vertical_speed",   false);
 207     ADD_VOICE(Voices.pMaintVSpeed,    "maintain_vertical_speed", false);
 208     ADD_VOICE(Voices.pMonitorVSpeed,  "monitor_vertical_speed",  false);
 209     ADD_VOICE(Voices.pLevelOff,       "level_off",               false);
 210     ADD_VOICE(Voices.pTestOk,         "test_ok",                 false);
 211     ADD_VOICE(Voices.pTestFail,       "test_fail",               false);
 212
 213     speaker.update_configuration();
 214 }
 215
 216 /////////////////////////////////////////////////////////////////////////////
 217 // TCAS::Annunciator ////////////////////////////////////////////////////////
 218 /////////////////////////////////////////////////////////////////////////////
 219
 220 TCAS::Annunciator::Annunciator(TCAS* _tcas) :
 221     tcas(_tcas),
 222     pLastVoice(NULL),
 223     voicePlayer(_tcas)
 224 {
 225     clear();
 226 }
 227
 228 void TCAS::Annunciator::clear(void)
 229 {
 230     previous.threatLevel = ThreatNone;
 231     previous.RA          = AdvisoryClear;
 232     previous.RAOption    = OptionNone;
 233     pLastVoice = NULL;
 234 }
 235
 236 void
 237 TCAS::Annunciator::bind(SGPropertyNode* node)
 238 {
 239     voicePlayer.bind(node, "Sounds/tcas/female/");
 240 }
 241
 242 void
 243 TCAS::Annunciator::init(void)
 244 {
 245     //TODO link to GPWS module/audio-on signal must be configurable
 246     nodeGpwsAlertOn = fgGetNode("/instrumentation/mk-viii/outputs/discretes/audio-on", true);
 247     voicePlayer.init();
 248 }
 249
 250 void
 251 TCAS::Annunciator::update(void)
 252 {
 253     voicePlayer.update();
 254
 255     /* [TCASII]: "The priority scheme gives ground proximity warning systems (GPWS)
 256      *   a higher annunciation priority than a TCAS alert. TCAS aural annunciation will
 257      *   be inhibited during the time that a GPWS alert is active." */
 258     if (nodeGpwsAlertOn->getBoolValue())
 259         voicePlayer.pause();
 260     else
 261         voicePlayer.resume();
 262 }
 263
 264 /** Trigger voice sample for current alert. */
 265 void
 266 TCAS::Annunciator::trigger(const ResolutionAdvisory& current, bool revertedRA)
 267 {
 268     int RA = current.RA;
 269     int RAOption = current.RAOption;
 270
 271     if (RA == AdvisoryClear)
 272     {
 273         if (previous.RA != AdvisoryClear)
 274         {
 275             voicePlayer.play(voicePlayer.Voices.pClear, VoicePlayer::PLAY_NOW);
 276             previous = current;
 277         }
 278         pLastVoice = NULL;
 279         return;
 280     }
 281
 282     if ((previous.RA == AdvisoryClear)||
 283         (tcas->tracker.newTraffic()))
 284     {
 285         voicePlayer.play(voicePlayer.Voices.pTrafficTraffic, VoicePlayer::PLAY_NOW);
 286     }
 287
 288     // pick voice sample
 289     VoicePlayer::Voice* pVoice = NULL;
 290     switch(RA)
 291     {
 292         case AdvisoryClimb:
 293             if (revertedRA)
 294                 pVoice = voicePlayer.Voices.pClimbNow;
 295             else
 296             if (AVAILABLE_RA(RAOption, OptionIncreaseClimb))
 297                 pVoice = voicePlayer.Voices.pClimbIncrease;
 298             else
 299             if (AVAILABLE_RA(RAOption, OptionCrossingClimb))
 300                 pVoice = voicePlayer.Voices.pClimbCrossing;
 301             else
 302                 pVoice = voicePlayer.Voices.pClimb;
 303             break;
 304
 305         case AdvisoryDescend:
 306             if (revertedRA)
 307                 pVoice = voicePlayer.Voices.pDescendNow;
 308             else
 309             if (AVAILABLE_RA(RAOption, OptionIncreaseDescend))
 310                 pVoice = voicePlayer.Voices.pDescendIncrease;
 311             else
 312             if (AVAILABLE_RA(RAOption, OptionCrossingDescent))
 313                 pVoice = voicePlayer.Voices.pDescendCrossing;
 314             else
 315                 pVoice = voicePlayer.Voices.pDescend;
 316             break;
 317
 318         case AdvisoryAdjustVSpeed:
 319             pVoice = voicePlayer.Voices.pAdjustVSpeed;
 320             break;
 321
 322         case AdvisoryMaintVSpeed:
 323             pVoice = voicePlayer.Voices.pMaintVSpeed;
 324             break;
 325
 326         case AdvisoryMonitorVSpeed:
 327             pVoice = voicePlayer.Voices.pMonitorVSpeed;
 328             break;
 329
 330         case AdvisoryLevelOff:
 331             pVoice = voicePlayer.Voices.pLevelOff;
 332             break;
 333
 334         case AdvisoryIntrusion:
 335             break;
 336
 337         default:
 338             RA = AdvisoryIntrusion;
 339             break;
 340     }
 341
 342     previous = current;
 343
 344     if ((pLastVoice == pVoice)&&
 345         (!tcas->tracker.newTraffic()))
 346     {
 347         // don't repeat annunciation
 348         return;
 349     }
 350     pLastVoice = pVoice;
 351     if (pVoice)
 352         voicePlayer.play(pVoice);
 353
 354 #ifdef FEATURE_TCAS_DEBUG_ANNUNCIATOR
 355     cout << "Annunciating TCAS RA " << RA << endl;
 356 #endif
 357 }
 358
 359 void
 360 TCAS::Annunciator::test(bool testOk)
 361 {
 362     if (testOk)
 363         voicePlayer.play(voicePlayer.Voices.pTestOk);
 364     else
 365         voicePlayer.play(voicePlayer.Voices.pTestFail);
 366 }
 367
 368 /////////////////////////////////////////////////////////////////////////////
 369 // TCAS::AdvisoryCoordinator ////////////////////////////////////////////////
 370 /////////////////////////////////////////////////////////////////////////////
 371
 372 TCAS::AdvisoryCoordinator::AdvisoryCoordinator(TCAS* _tcas) :
 373   tcas(_tcas),
 374   lastTATime(0)
 375 {
 376     init();
 377 }
 378
 379 void
 380 TCAS::AdvisoryCoordinator::init(void)
 381 {
 382     reinit();
 383 }
 384
 385 void
 386 TCAS::AdvisoryCoordinator::reinit(void)
 387 {
 388     clear();
 389     previous = current;
 390 }
 391
 392 void
 393 TCAS::AdvisoryCoordinator::bind(SGPropertyNode* node)
 394 {
 395     nodeTAWarning = node->getNode("outputs/traffic-alert", true);
 396     nodeTAWarning->setBoolValue(false);
 397 }
 398
 399 void
 400 TCAS::AdvisoryCoordinator::clear(void)
 401 {
 402     current.threatLevel = ThreatNone;
 403     current.RA          = AdvisoryClear;
 404     current.RAOption    = OptionNone;
 405 }
 406
 407 /** Add all suitable resolution advisories for a single threat. */
 408 void
 409 TCAS::AdvisoryCoordinator::add(const ResolutionAdvisory& newAdvisory)
 410 {
 411     if ((newAdvisory.RA == AdvisoryClear)||
 412         (newAdvisory.threatLevel < current.threatLevel))
 413         return;
 414
 415     if (current.threatLevel == newAdvisory.threatLevel)
 416     {
 417         // combine with other advisories so far
 418         current.RA &= newAdvisory.RA;
 419         // remember any advisory modifier
 420         current.RAOption |= newAdvisory.RAOption;
 421     }
 422     else
 423     {
 424         current = newAdvisory;
 425     }
 426 }
 427
 428 /** Pick and trigger suitable resolution advisory. */
 429 void
 430 TCAS::AdvisoryCoordinator::update(int mode)
 431 {
 432     bool revertedRA = false; // has advisory changed?
 433     double currentTime = globals->get_sim_time_sec();
 434
 435     if (current.RA == AdvisoryClear)
 436     {
 437         // filter: wait 5 seconds after last TA/RA before announcing TA clearance
 438         if ((previous.RA != AdvisoryClear)&&
 439              (currentTime - lastTATime < 5.0))
 440             return;
 441     }
 442     else
 443     {
 444         // intruder detected
 445
 446 #ifdef FEATURE_TCAS_DEBUG_COORDINATOR
 447         cout << "TCAS::Annunciator::update: previous: " << previous.RA << ", new: " << current.RA << endl;
 448 #endif
 449
 450         lastTATime = currentTime;
 451         if ((previous.RA == AdvisoryClear)||
 452             (previous.RA == AdvisoryIntrusion)||
 453             ((current.RA & previous.RA) != previous.RA))
 454         {
 455             // no RA yet, or we can't keep previous RA: pick one - in order of priority
 456
 457             if (AVAILABLE_RA(current.RA, AdvisoryMonitorVSpeed))
 458             {
 459                 // prio 1: monitor vertical speed only
 460                 current.RA = AdvisoryMonitorVSpeed;
 461             }
 462             else
 463             if (AVAILABLE_RA(current.RA, AdvisoryMaintVSpeed))
 464             {
 465                 // prio 2: maintain vertical speed
 466                 current.RA = AdvisoryMaintVSpeed;
 467             }
 468             else
 469             if (AVAILABLE_RA(current.RA, AdvisoryAdjustVSpeed))
 470             {
 471                 // prio 3: adjust vertical speed (TCAS II 7.0 only)
 472                 current.RA = AdvisoryAdjustVSpeed;
 473             }
 474             else
 475             if (AVAILABLE_RA(current.RA, AdvisoryLevelOff))
 476             {
 477                 // prio 3: adjust vertical speed (TCAS II 7.1 only, [EUROACAS]: CP115)
 478                 current.RA = AdvisoryLevelOff;
 479             }
 480             else
 481             if (AVAILABLE_RA(current.RA, AdvisoryClimb))
 482             {
 483                 // prio 4: climb
 484                 current.RA = AdvisoryClimb;
 485             }
 486             else
 487             if (AVAILABLE_RA(current.RA, AdvisoryDescend))
 488             {
 489                 // prio 5: descend
 490                 current.RA = AdvisoryDescend;
 491             }
 492             else
 493             {
 494                 // no RA, issue a TA only
 495                 current.RA = AdvisoryIntrusion;
 496             }
 497
 498             // check if earlier advisory was reverted
 499             revertedRA = ((previous.RA != current.RA)&&
 500                           (previous.RA != 0)&&
 501                           (previous.RA != AdvisoryIntrusion));
 502         }
 503         else
 504         {
 505             // keep earlier RA
 506             current.RA = previous.RA;
 507         }
 508     }
 509
 510     /* [TCASII]: "Aural annunciations are inhibited below 500+/-100 feet AGL." */
 511     if ((tcas->threatDetector.getRadarAlt() > 500)&&
 512         (mode >= SwitchTaOnly))
 513         tcas->annunciator.trigger(current, revertedRA);
 514     else
 515     if (current.RA == AdvisoryClear)
 516     {
 517         /* explicitly clear traffic alert (since aural annunciation disabled) */
 518         tcas->annunciator.clear();
 519     }
 520
 521     previous = current;
 522
 523     /* [TCASII] "[..] also performs the function of setting flags that control the displays.
 524      *   The traffic display, the RA display, [..] use these flags to alert the pilot to
 525      *   the presence of TAs and RAs." */
 526     nodeTAWarning->setBoolValue(current.RA != AdvisoryClear);
 527 }
 528
 529 ///////////////////////////////////////////////////////////////////////////////
 530 // TCAS::ThreatDetector ///////////////////////////////////////////////////////
 531 ///////////////////////////////////////////////////////////////////////////////
 532
 533 TCAS::ThreatDetector::ThreatDetector(TCAS* _tcas) :
 534     tcas(_tcas),
 535     checkCount(0),
 536     pAlarmThresholds(&sensitivityLevels[0])
 537 {
 538     self.radarAltFt = 0.0;
 539     unitTest();
 540 }
 541
 542 void
 543 TCAS::ThreatDetector::init(void)
 544 {
 545     nodeLat         = fgGetNode("/position/latitude-deg",          true);
 546     nodeLon         = fgGetNode("/position/longitude-deg",         true);
 547     nodePressureAlt = fgGetNode("/position/altitude-ft",           true);
 548     nodeRadarAlt    = fgGetNode("/position/altitude-agl-ft",       true);
 549     nodeHeading     = fgGetNode("/orientation/heading-deg",        true);
 550     nodeVelocity    = fgGetNode("/velocities/airspeed-kt",         true);
 551     nodeVerticalFps = fgGetNode("/velocities/vertical-speed-fps",  true);
 552
 553     tcas->advisoryGenerator.init(&self,&currentThreat);
 554 }
 555
 556 /** Update local position and threat sensitivity levels. */
 557 void
 558 TCAS::ThreatDetector::update(void)
 559 {
 560     // update local position
 561     self.lat           = nodeLat->getDoubleValue();
 562     self.lon           = nodeLon->getDoubleValue();
 563     self.pressureAltFt = nodePressureAlt->getDoubleValue();
 564     self.heading       = nodeHeading->getDoubleValue();
 565     self.velocityKt    = nodeVelocity->getDoubleValue();
 566     self.verticalFps   = nodeVerticalFps->getDoubleValue();
 567
 568     /* radar altimeter provides a lot of spikes due to uneven terrain
 569      * MK-VIII GPWS-spec requires smoothing the radar altitude with a
 570      * 10second moving average. Likely the TCAS spec requires the same.
 571      * => We use a cheap 10 second exponential average method.
 572      */
 573     const double SmoothingFactor = 0.3;
 574     self.radarAltFt = nodeRadarAlt->getDoubleValue()*SmoothingFactor +
 575             (1-SmoothingFactor)*self.radarAltFt;
 576
 577 #ifdef FEATURE_TCAS_DEBUG_THREAT_DETECTOR
 578     printf("TCAS::ThreatDetector::update: radarAlt = %f\n",self.radarAltFt);
 579     checkCount = 0;
 580 #endif
 581
 582     // determine current altitude's "Sensitivity Level Definition and Alarm Thresholds"
 583     int sl=0;
 584     for (sl=0;((self.radarAltFt > sensitivityLevels[sl].maxAltitude)&&
 585                (sensitivityLevels[sl].maxAltitude));sl++);
 586     pAlarmThresholds = &sensitivityLevels[sl];
 587     tcas->advisoryGenerator.setAlarmThresholds(pAlarmThresholds);
 588 }
 589
 590 /** Check if plane's transponder is enabled. */
 591 bool
 592 TCAS::ThreatDetector::checkTransponder(const SGPropertyNode* pModel, float velocityKt)
 593 {
 594     const string name = pModel->getName();
 595     if (name != "multiplayer" && name != "aircraft")
 596     {
 597         // assume non-MP/non-AI planes (e.g. ships) have no transponder
 598         return false;
 599     }
 600
 601     if (velocityKt < 40)
 602     {
 603         /* assume all pilots have their transponder switched off while taxiing/parking
 604          * (at low speed) */
 605         return false;
 606     }
 607
 608     if ((name == "multiplayer")&&
 609         (pModel->getBoolValue("controls/invisible")))
 610     {
 611         // ignored MP plane: pretend transponder is switched off
 612         return false;
 613     }
 614
 615     return true;
 616 }
 617
 618 /** Check if plane is a threat. */
 619 int
 620 TCAS::ThreatDetector::checkThreat(int mode, const SGPropertyNode* pModel)
 621 {
 622 #ifdef FEATURE_TCAS_DEBUG_THREAT_DETECTOR
 623     checkCount++;
 624 #endif
 625
 626     float velocityKt  = pModel->getDoubleValue("velocities/true-airspeed-kt");
 627
 628     if (!checkTransponder(pModel, velocityKt))
 629         return ThreatInvisible;
 630
 631     int threatLevel = ThreatNone;
 632     float altFt = pModel->getDoubleValue("position/altitude-ft");
 633     currentThreat.relativeAltitudeFt = altFt - self.pressureAltFt;
 634
 635     // save computation time: don't care when relative altitude is excessive
 636     if (fabs(currentThreat.relativeAltitudeFt) > 10000)
 637         return threatLevel;
 638
 639     // position data of current intruder
 640     double lat        = pModel->getDoubleValue("position/latitude-deg");
 641     double lon        = pModel->getDoubleValue("position/longitude-deg");
 642     float heading     = pModel->getDoubleValue("orientation/true-heading-deg");
 643
 644     double distanceNm, bearing;
 645     calcRangeBearing(self.lat, self.lon, lat, lon, distanceNm, bearing);
 646
 647     // save computation time: don't care for excessive distances (also captures NaNs...)
 648     if ((distanceNm > 10)||(distanceNm < 0))
 649         return threatLevel;
 650
 651     currentThreat.verticalFps = pModel->getDoubleValue("velocities/vertical-speed-fps");
 652
 653     /* Detect proximity targets
 654      * [TCASII]: "Any target that is less than 6 nmi in range and within +/-1200ft
 655      *  vertically, but that does not meet the intruder or threat criteria." */
 656     if ((distanceNm < 6)&&
 657         (fabs(currentThreat.relativeAltitudeFt) < 1200))
 658     {
 659         // at least a proximity target
 660         threatLevel = ThreatProximity;
 661     }
 662
 663     /* do not detect any threats when in standby or on ground and taxiing */
 664     if ((mode <= SwitchStandby)||
 665         ((self.radarAltFt < 360)&&(self.velocityKt < 40)))
 666     {
 667         return threatLevel;
 668     }
 669
 670     if (tcas->tracker.active())
 671     {
 672         currentThreat.callsign = pModel->getStringValue("callsign");
 673         currentThreat.isTracked = tcas->tracker.isTracked(currentThreat.callsign);
 674     }
 675     else
 676         currentThreat.isTracked = false;
 677
 678     // first stage: vertical movement
 679     checkVerticalThreat();
 680
 681     // stop processing when no vertical threat
 682     if ((!currentThreat.verticalTA)&&
 683         (!currentThreat.isTracked))
 684         return threatLevel;
 685
 686     // second stage: horizontal movement
 687     horizontalThreat(bearing, distanceNm, heading, velocityKt);
 688
 689     if (!currentThreat.isTracked)
 690     {
 691         // no horizontal threat?
 692         if (!currentThreat.horizontalTA)
 693             return threatLevel;
 694
 695         if ((currentThreat.horizontalTau < 0)||
 696             (currentThreat.verticalTau < 0))
 697         {
 698             // do not trigger new alerts when Tau is negative, but keep existing alerts
 699             int previousThreatLevel = pModel->getIntValue("tcas/threat-level", 0);
 700             if (previousThreatLevel == 0)
 701                 return threatLevel;
 702         }
 703     }
 704
 705 #ifdef FEATURE_TCAS_DEBUG_THREAT_DETECTOR
 706     cout << "#" << checkCount << ": " << pModel->getStringValue("callsign") << endl;
 707 #endif
 708
 709
 710     /* [TCASII]: "For either a TA or an RA to be issued, both the range and
 711      *    vertical criteria, in terms of tau or the fixed thresholds, must be
 712      *    satisfied only one of the criteria is satisfied, TCAS will not issue
 713      *    an advisory." */
 714     if (currentThreat.horizontalTA && currentThreat.verticalTA)
 715         threatLevel = ThreatTA;
 716     if (currentThreat.horizontalRA && currentThreat.verticalRA)
 717         threatLevel = ThreatRA;
 718
 719     if (!tcas->tracker.active())
 720         currentThreat.callsign = pModel->getStringValue("callsign");
 721
 722     tcas->tracker.add(currentThreat.callsign, threatLevel);
 723
 724     // check existing threat level
 725     if (currentThreat.isTracked)
 726     {
 727         int oldLevel = tcas->tracker.getThreatLevel(currentThreat.callsign);
 728         if (oldLevel > threatLevel)
 729             threatLevel = oldLevel;
 730     }
 731
 732     // find all resolution options for this conflict
 733     threatLevel = tcas->advisoryGenerator.resolution(mode, threatLevel, distanceNm, altFt, heading, velocityKt);
 734
 735
 736 #ifdef FEATURE_TCAS_DEBUG_THREAT_DETECTOR
 737     printf("  threat: distance: %4.1f, bearing: %4.1f, alt: %5.1f, velocity: %4.1f, heading: %4.1f, vspeed: %4.1f, "
 738            "own alt: %5.1f, own heading: %4.1f, own velocity: %4.1f, vertical tau: %3.2f"
 739            //", closing speed: %f"
 740            "\n",
 741            distanceNm, relAngle(bearing, self.heading), altFt, velocityKt, heading, currentThreat.verticalFps,
 742            self.altFt, self.heading, self.velocityKt
 743            //, currentThreat.closingSpeedKt
 744            ,currentThreat.verticalTau
 745            );
 746 #endif
 747
 748     return threatLevel;
 749 }
 750
 751 /** Check if plane is a vertical threat. */
 752 void
 753 TCAS::ThreatDetector::checkVerticalThreat(void)
 754 {
 755     // calculate relative vertical speed and altitude
 756     float dV = self.verticalFps - currentThreat.verticalFps;
 757     float dA = currentThreat.relativeAltitudeFt;
 758
 759     currentThreat.verticalTA  = false;
 760     currentThreat.verticalRA  = false;
 761     currentThreat.verticalTau = 0;
 762
 763     /* [TCASII]: "The vertical tau is equal to the altitude separation (feet)
 764      *   divided by the combined vertical speed of the two aircraft (feet/minute)
 765      *   times 60." */
 766     float tau = 0;
 767     if (fabs(dV) > 0.1)
 768         tau = dA/dV;
 769
 770     /* [TCASII]: "When the combined vertical speed of the TCAS and the intruder aircraft
 771      *    is low, TCAS will use a fixed-altitude threshold to determine whether a TA or
 772      *    an RA should be issued." */
 773     if ((fabs(dV) < 3.0)||
 774         ((tau < 0) && (tau > -5)))
 775     {
 776         /* vertical closing speed is low (below 180fpm/3fps), check
 777          * fixed altitude range. */
 778         float abs_dA = fabs(dA);
 779         if (abs_dA < pAlarmThresholds->RA.ALIM)
 780         {
 781             // continuous intrusion at RA-level
 782             currentThreat.verticalTA = true;
 783             currentThreat.verticalRA = true;
 784         }
 785         else
 786         if (abs_dA < pAlarmThresholds->TA.ALIM)
 787         {
 788             // continuous intrusion: with TA-level, but no RA-threat
 789             currentThreat.verticalTA = true;
 790         }
 791         // else: no RA/TA threat
 792     }
 793     else
 794     {
 795         if ((tau < pAlarmThresholds->TA.Tau)&&
 796             (tau >= -5))
 797         {
 798             currentThreat.verticalTA = true;
 799             currentThreat.verticalRA = (tau < pAlarmThresholds->RA.Tau);
 800         }
 801     }
 802     currentThreat.verticalTau = tau;
 803
 804 #ifdef FEATURE_TCAS_DEBUG_THREAT_DETECTOR
 805     if (currentThreat.verticalTA)
 806         printf("  vertical dV=%f (%f-%f), dA=%f\n", dV, self.verticalFps, currentThreat.verticalFps, dA);
 807 #endif
 808 }
 809
 810 /** Check if plane is a horizontal threat. */
 811 void
 812 TCAS::ThreatDetector::horizontalThreat(float bearing, float distanceNm, float heading, float velocityKt)
 813 {
 814     // calculate speed
 815     float vxKt = sin(heading*SGD_DEGREES_TO_RADIANS)*velocityKt - sin(self.heading*SGD_DEGREES_TO_RADIANS)*self.velocityKt;
 816     float vyKt = cos(heading*SGD_DEGREES_TO_RADIANS)*velocityKt - cos(self.heading*SGD_DEGREES_TO_RADIANS)*self.velocityKt;
 817
 818     // calculate horizontal closing speed
 819     float closingSpeedKt2 = vxKt*vxKt+vyKt*vyKt;
 820     float closingSpeedKt  = sqrt(closingSpeedKt2);
 821
 822     /* [TCASII]: "The range tau is equal to the slant range (nmi) divided by the closing speed
 823      *    (knots) multiplied by 3600."
 824      * => calculate allowed slant range (nmi) based on known maximum tau */
 825     float TA_rangeNm = (pAlarmThresholds->TA.Tau*closingSpeedKt)/3600;
 826     float RA_rangeNm = (pAlarmThresholds->RA.Tau*closingSpeedKt)/3600;
 827
 828     if (closingSpeedKt < 100)
 829     {
 830         /* [TCASII]: "In events where the rate of closure is very low, [..]
 831          *    an intruder aircraft can come very close in range without crossing the
 832          *    range tau boundaries [..]. To provide protection in these types of
 833          *    advisories, the range tau boundaries are modified [..] to use
 834          *    a fixed-range threshold to issue TAs and RAs in these slow closure
 835          *    encounters." */
 836         TA_rangeNm += (100.0-closingSpeedKt)*(pAlarmThresholds->TA.DMOD/100.0);
 837         RA_rangeNm += (100.0-closingSpeedKt)*(pAlarmThresholds->RA.DMOD/100.0);
 838     }
 839     if (TA_rangeNm < pAlarmThresholds->TA.DMOD)
 840         TA_rangeNm = pAlarmThresholds->TA.DMOD;
 841     if (RA_rangeNm < pAlarmThresholds->RA.DMOD)
 842         RA_rangeNm = pAlarmThresholds->RA.DMOD;
 843
 844     currentThreat.horizontalTA   = (distanceNm < TA_rangeNm);
 845     currentThreat.horizontalRA   = (distanceNm < RA_rangeNm);
 846     currentThreat.horizontalTau  = -1;
 847
 848     if ((currentThreat.horizontalRA)&&
 849         (currentThreat.verticalRA))
 850     {
 851         /* an RA will be issued. Prepare extra data for the
 852          * traffic resolution stage, i.e. calculate
 853          * exact time tau to horizontal CPA.
 854          */
 855
 856         /* relative position of intruder is
 857          *   Sx(t) = sx + vx*t
 858          *   Sy(t) = sy + vy*t
 859          * horizontal distance to intruder is r(t)
 860          *   r(t) = sqrt( Sx(t)^2 + Sy(t)^2 )
 861          * => horizontal CPA at time t=tau, where r(t) has minimum
 862          * r2(t) := r^2(t) = Sx(t)^2 + Sy(t)^2
 863          * since r(t)>0 for all t => minimum of r(t) is also minimum of r2(t)
 864          * => (d/dt) r2(t) = r2'(t) is 0 for t=tau
 865          *    r2(t) = ((Sx(t)^2 + Sy(t))^2) = c + b*t + a*t^2
 866          * => r2'(t) = b + a*2*t
 867          * at t=tau:
 868          *    r2'(tau) = 0 = b + 2*a*tau
 869          * => tau = -b/(2*a)
 870          */
 871         float sx = sin(bearing*SGD_DEGREES_TO_RADIANS)*distanceNm;
 872         float sy = cos(bearing*SGD_DEGREES_TO_RADIANS)*distanceNm;
 873         float vx = vxKt * (SG_KT_TO_MPS*SG_METER_TO_NM);
 874         float vy = vyKt * (SG_KT_TO_MPS*SG_METER_TO_NM);
 875         float a  = vx*vx + vy*vy;
 876         float b  = 2*(sx*vx + sy*vy);
 877         float tau = 0;
 878         if (a > 0.0001)
 879             tau = -b/(2*a);
 880 #ifdef FEATURE_TCAS_DEBUG_THREAT_DETECTOR
 881         printf("  Time to horizontal CPA: %4.2f\n",tau);
 882 #endif
 883         if (tau > pAlarmThresholds->RA.Tau)
 884             tau = pAlarmThresholds->RA.Tau;
 885
 886         // remember time to horizontal CPA
 887         currentThreat.horizontalTau = tau;
 888     }
 889 }
 890
 891 /** Test threat detection logic. */
 892 void
 893 TCAS::ThreatDetector::unitTest(void)
 894 {
 895     pAlarmThresholds = &sensitivityLevels[1];
 896 #if 0
 897     // vertical tests
 898     self.verticalFps = 0;
 899     self.altFt = 1000;
 900     cout << "identical altitude and vspeed " << endl;
 901     checkVerticalThreat(self.altFt, self.verticalFps);
 902     cout << "1000ft alt offset, dV=100 " << endl;
 903     checkVerticalThreat(self.altFt+1000, 100);
 904     cout << "-1000ft alt offset, dV=100 " << endl;
 905     checkVerticalThreat(self.altFt-1000, 100);
 906     cout << "3000ft alt offset, dV=10 " << endl;
 907     checkVerticalThreat(self.altFt+3000, 10);
 908     cout << "500ft alt offset, dV=100 " << endl;
 909     checkVerticalThreat(self.altFt+500, 100);
 910     cout << "500ft alt offset, dV=-100 " << endl;
 911     checkVerticalThreat(self.altFt+500, -100);
 912
 913     // horizontal tests
 914     self.heading = 0;
 915     self.velocityKt = 0;
 916     cout << "10nm behind, overtaking with 1Nm/s" << endl;
 917     horizontalThreat(-180, 10, 0, 1/(SG_KT_TO_MPS*SG_METER_TO_NM));
 918
 919     cout << "10nm ahead, departing with 1Nm/s" << endl;
 920     horizontalThreat(0, 20, 0, 1/(SG_KT_TO_MPS*SG_METER_TO_NM));
 921
 922     self.heading = 90;
 923     self.velocityKt = 1/(SG_KT_TO_MPS*SG_METER_TO_NM);
 924     cout << "10nm behind, overtaking with 1Nm/s at 90 degrees" << endl;
 925     horizontalThreat(-90, 20, 90, 2/(SG_KT_TO_MPS*SG_METER_TO_NM));
 926
 927     self.heading = 20;
 928     self.velocityKt = 1/(SG_KT_TO_MPS*SG_METER_TO_NM);
 929     cout << "10nm behind, overtaking with 1Nm/s at 20 degrees" << endl;
 930     horizontalThreat(200, 20, 20, 2/(SG_KT_TO_MPS*SG_METER_TO_NM));
 931 #endif
 932 }
 933
 934 ///////////////////////////////////////////////////////////////////////////////
 935 // TCAS::AdvisoryGenerator ////////////////////////////////////////////////////
 936 ///////////////////////////////////////////////////////////////////////////////
 937
 938 TCAS::AdvisoryGenerator::AdvisoryGenerator(TCAS* _tcas) :
 939     tcas(_tcas),
 940     pSelf(NULL),
 941     pCurrentThreat(NULL),
 942     pAlarmThresholds(NULL)
 943 {
 944 }
 945
 946 void
 947 TCAS::AdvisoryGenerator::init(const LocalInfo* _pSelf, ThreatInfo* _pCurrentThreat)
 948 {
 949     pCurrentThreat = _pCurrentThreat;
 950     pSelf = _pSelf;
 951 }
 952
 953 void
 954 TCAS::AdvisoryGenerator::setAlarmThresholds(const SensitivityLevel* _pAlarmThresholds)
 955 {
 956     pAlarmThresholds = _pAlarmThresholds;
 957 }
 958
 959 /** Calculate projected vertical separation at horizontal CPA. */
 960 float
 961 TCAS::AdvisoryGenerator::verticalSeparation(float newVerticalFps)
 962 {
 963     // calculate relative vertical speed and altitude
 964     float dV = pCurrentThreat->verticalFps - newVerticalFps;
 965     float tau = pCurrentThreat->horizontalTau;
 966     // don't use negative tau to project future separation...
 967     if (tau < 0.5)
 968         tau = 0.5;
 969     return pCurrentThreat->relativeAltitudeFt + tau * dV;
 970 }
 971
 972 /** Determine RA sense. */
 973 void
 974 TCAS::AdvisoryGenerator::determineRAsense(int& RASense, bool& isCrossing)
 975 {
 976     /* [TCASII]: "[..] a two step process is used to select the appropriate RA for the encounter
 977              *   geometry. The first step in the process is to select the RA sense, i.e., upward or downward." */
 978     RASense = 0;
 979     isCrossing = false;
 980
 981     /* [TCASII]: "Based on the range and altitude tracks of the intruder, the CAS logic models the
 982      *   intruder's flight path from its present position to CPA. The CAS logic then models upward
 983      *   and downward sense RAs for own aircraft [..] to determine which sense provides the most
 984      *   vertical separation at CPA." */
 985     float upSenseRelAltFt   = verticalSeparation(+2000/60.0);
 986     float downSenseRelAltFt = verticalSeparation(-2000/60.0);
 987     if (fabs(upSenseRelAltFt) >= fabs(downSenseRelAltFt))
 988         RASense = +1;  // upward
 989     else
 990         RASense = -1; // downward
 991
 992     /* [TCASII]: "In encounters where either of the senses results in the TCAS aircraft crossing through
 993      *   the intruder's altitude, TCAS is designed to select the nonaltitude crossing sense if the
 994      *   noncrossing sense provides the desired vertical separation, known as ALIM, at CPA." */
 995     /* [TCASII]: "If ALIM cannot be obtained in the nonaltitude crossing sense, an altitude
 996      *   crossing RA will be issued." */
 997     if ((RASense > 0)&&
 998         (pCurrentThreat->relativeAltitudeFt > 200))
 999     {
1000         // threat is above and RA is crossing
1001         if (fabs(downSenseRelAltFt) > pAlarmThresholds->TA.ALIM)
1002         {
1003             // non-crossing descend is sufficient
1004             RASense = -1;
1005         }
1006         else
1007         {
1008             // keep crossing climb RA
1009             isCrossing = true;
1010         }
1011     }
1012     else
1013     if ((RASense < 0)&&
1014         (pCurrentThreat->relativeAltitudeFt < -200))
1015     {
1016         // threat is below and RA is crossing
1017         if (fabs(upSenseRelAltFt) > pAlarmThresholds->TA.ALIM)
1018         {
1019             // non-crossing climb is sufficient
1020             RASense = 1;
1021         }
1022         else
1023         {
1024             // keep crossing descent RA
1025             isCrossing = true;
1026         }
1027     }
1028     // else: threat is at same altitude, keep optimal RA sense (non-crossing)
1029
1030     pCurrentThreat->RASense = RASense;
1031
1032 #ifdef FEATURE_TCAS_DEBUG_ADV_GENERATOR
1033         printf("  RASense: %i, crossing: %u, relAlt: %4.1f, upward separation: %4.1f, downward separation: %4.1f\n",
1034                RASense,isCrossing,
1035                pCurrentThreat->relativeAltitudeFt,
1036                upSenseRelAltFt,downSenseRelAltFt);
1037 #endif
1038 }
1039
1040 /** Determine suitable resolution advisories. */
1041 int
1042 TCAS::AdvisoryGenerator::resolution(int mode, int threatLevel, float rangeNm, float altFt,
1043                                     float heading, float velocityKt)
1044 {
1045     int RAOption = OptionNone;
1046     int RA       = AdvisoryIntrusion;
1047
1048     // RAs are disabled under certain conditions
1049     if (threatLevel == ThreatRA)
1050     {
1051         /* [TCASII]: "... less than 360 feet, TCAS considers the reporting aircraft
1052          *   to be on the ground. If TCAS determines the intruder to be on the ground, it
1053          *   inhibits the generation of advisories against this aircraft."*/
1054         if (altFt < 360)
1055             threatLevel = ThreatTA;
1056
1057         /* [EUROACAS]: "Certain RAs are inhibited at altitudes based on inputs from the radio altimeter:
1058          *   [..] (c)1000ft (+/- 100ft) and below, all RAs are inhibited;" */
1059         if (pSelf->radarAltFt < 1000)
1060             threatLevel = ThreatTA;
1061
1062         // RAs only issued in mode "Auto" (= "TA/RA" mode)
1063         if (mode != SwitchAuto)
1064             threatLevel = ThreatTA;
1065     }
1066
1067     bool isCrossing = false;
1068     int RASense = 0;
1069     // determine suitable RAs
1070     if (threatLevel == ThreatRA)
1071     {
1072         /* [TCASII]: "[..] a two step process is used to select the appropriate RA for the encounter
1073          *   geometry. The first step in the process is to select the RA sense, i.e., upward or downward." */
1074         determineRAsense(RASense, isCrossing);
1075
1076         /* second step: determine required strength */
1077         if (RASense > 0)
1078         {
1079             // upward
1080
1081             if ((pSelf->verticalFps < -1000/60.0)&&
1082                 (!isCrossing))
1083             {
1084                 // currently descending, see if reducing current descent is sufficient
1085                 float relAltFt = verticalSeparation(-500/60.0);
1086                 if (relAltFt > pAlarmThresholds->TA.ALIM)
1087                     RA |= AdvisoryAdjustVSpeed;
1088             }
1089             RA |= AdvisoryClimb;
1090             if (isCrossing)
1091                 RAOption |= OptionCrossingClimb;
1092         }
1093
1094         if (RASense < 0)
1095         {
1096             // downward
1097
1098             if ((pSelf->verticalFps > 1000/60.0)&&
1099                 (!isCrossing))
1100             {
1101                 // currently climbing, see if reducing current climb is sufficient
1102                 float relAltFt = verticalSeparation(500/60.0);
1103                 if (relAltFt < -pAlarmThresholds->TA.ALIM)
1104                     RA |= AdvisoryAdjustVSpeed;
1105             }
1106             RA |= AdvisoryDescend;
1107             if (isCrossing)
1108                 RAOption |= OptionCrossingDescent;
1109         }
1110
1111         //TODO
1112         /* [TCASII]: "When two TCAS-equipped aircraft are converging vertically with opposite rates
1113          *   and are currently well separated in altitude, TCAS will first issue a vertical speed
1114          *   limit (Negative) RA to reinforce the pilots' likely intention to level off at adjacent
1115          *   flight levels." */
1116
1117         //TODO
1118         /* [TCASII]: "[..] if the CAS logic determines that the response to a Positive RA has provided
1119          *   ALIM feet of vertical separation before CPA, the initial RA will be weakened to either a
1120          *   Do Not Descend RA (after an initial Climb RA) or a Do Not Climb RA (after an initial
1121          *   Descend RA)." */
1122
1123         //TODO
1124         /* [TCASII]: "TCAS is designed to inhibit Increase Descent RAs below 1450 feet AGL; */
1125
1126         /* [TCASII]: "Descend RAs below 1100 feet AGL;" (inhibited) */
1127         if (pSelf->radarAltFt < 1100)
1128         {
1129             RA &= ~AdvisoryDescend;
1130             //TODO Support "Do not descend" RA
1131             RA |= AdvisoryIntrusion;
1132         }
1133     }
1134
1135 #ifdef FEATURE_TCAS_DEBUG_ADV_GENERATOR
1136     cout << "  resolution advisory: " << RA << endl;
1137 #endif
1138
1139     ResolutionAdvisory newAdvisory;
1140     newAdvisory.RAOption    = RAOption;
1141     newAdvisory.RA          = RA;
1142     newAdvisory.threatLevel = threatLevel;
1143     tcas->advisoryCoordinator.add(newAdvisory);
1144
1145     return threatLevel;
1146 }
1147
1148 ///////////////////////////////////////////////////////////////////////////////
1149 // TCAS ///////////////////////////////////////////////////////////////////////
1150 ///////////////////////////////////////////////////////////////////////////////
1151
1152 TCAS::TCAS(SGPropertyNode* pNode) :
1153     name("tcas"),
1154     num(0),
1155     nextUpdateTime(0),
1156     selfTestStep(0),
1157     properties_handler(this),
1158     threatDetector(this),
1159     tracker(this),
1160     advisoryCoordinator(this),
1161     advisoryGenerator(this),
1162     annunciator(this)
1163 {
1164     for (int i = 0; i < pNode->nChildren(); ++i)
1165     {
1166         SGPropertyNode* pChild = pNode->getChild(i);
1167         string cname = pChild->getName();
1168         string cval = pChild->getStringValue();
1169
1170         if (cname == "name")
1171             name = cval;
1172         else if (cname == "number")
1173             num = pChild->getIntValue();
1174         else
1175         {
1176             SG_LOG(SG_INSTR, SG_WARN, "Error in TCAS config logic");
1177             if (name.length())
1178                 SG_LOG(SG_INSTR, SG_WARN, "Section = " << name);
1179         }
1180     }
1181 }
1182
1183 void
1184 TCAS::init(void)
1185 {
1186     annunciator.init();
1187     advisoryCoordinator.init();
1188     threatDetector.init();
1189 }
1190
1191 void
1192 TCAS::reinit(void)
1193 {
1194     nextUpdateTime = 0;
1195     advisoryCoordinator.reinit();
1196 }
1197
1198 void
1199 TCAS::bind(void)
1200 {
1201     SGPropertyNode* node = fgGetNode(("/instrumentation/" + name).c_str(), num, true);
1202
1203     nodeServiceable  = node->getNode("serviceable", true);
1204
1205     // TCAS mode selection (0=off, 1=standby, 2=TA only, 3=auto(TA/RA) )
1206     nodeModeSwitch   = node->getNode("inputs/mode", true);
1207     // self-test button
1208     nodeSelfTest     = node->getNode("inputs/self-test", true);
1209     // default value
1210     nodeSelfTest->setBoolValue(false);
1211
1212 #ifdef FEATURE_TCAS_DEBUG_PROPERTIES
1213     SGPropertyNode* nodeDebug = node->getNode("debug", true);
1214     // debug triggers
1215     nodeDebugTrigger = nodeDebug->getNode("threat-trigger", true);
1216     nodeDebugRA      = nodeDebug->getNode("threat-RA",      true);
1217     nodeDebugThreat  = nodeDebug->getNode("threat-level",   true);
1218     // default values
1219     nodeDebugTrigger->setBoolValue(false);
1220     nodeDebugRA->setIntValue(3);
1221     nodeDebugThreat->setIntValue(1);
1222 #endif
1223
1224     annunciator.bind(node);
1225     advisoryCoordinator.bind(node);
1226 }
1227
1228 void
1229 TCAS::unbind(void)
1230 {
1231     properties_handler.unbind();
1232 }
1233
1234 /** Monitor traffic for safety threats. */
1235 void
1236 TCAS::update(double dt)
1237 {
1238     if (!nodeServiceable->getBoolValue())
1239         return;
1240     int mode = nodeModeSwitch->getIntValue();
1241     if (mode == SwitchOff)
1242         return;
1243
1244     nextUpdateTime -= dt;
1245     if (nextUpdateTime <= 0.0 )
1246     {
1247         nextUpdateTime = 1.0;
1248
1249         // remove obsolete targets
1250         tracker.update();
1251
1252         // get aircrafts current position/speed/heading
1253         threatDetector.update();
1254
1255         // clear old threats
1256         advisoryCoordinator.clear();
1257
1258         if (nodeSelfTest->getBoolValue())
1259         {
1260             if (threatDetector.getVelocityKt() >= 40)
1261             {
1262                 // disable self-test when plane moves above taxiing speed
1263                 nodeSelfTest->setBoolValue(false);
1264                 selfTestStep = 0;
1265             }
1266             else
1267             {
1268                 selfTest();
1269                 // speed-up self test
1270                 nextUpdateTime = 0;
1271                 // no further TCAS processing during self-test
1272                 return;
1273             }
1274         }
1275
1276 #ifdef FEATURE_TCAS_DEBUG_PROPERTIES
1277         if (nodeDebugTrigger->getBoolValue())
1278         {
1279             // debugging test
1280             ResolutionAdvisory debugAdvisory;
1281             debugAdvisory.RAOption    = OptionNone;
1282             debugAdvisory.RA          = nodeDebugRA->getIntValue();
1283             debugAdvisory.threatLevel = nodeDebugThreat->getIntValue();
1284             advisoryCoordinator.add(debugAdvisory);
1285         }
1286         else
1287 #endif
1288         {
1289             SGPropertyNode* pAi = fgGetNode("/ai/models", true);
1290
1291             // check all aircraft
1292             for (int i = pAi->nChildren() - 1; i >= -1; i--)
1293             {
1294                 SGPropertyNode* pModel = pAi->getChild(i);
1295                 if ((pModel)&&(pModel->nChildren()))
1296                 {
1297                     int threatLevel = threatDetector.checkThreat(mode, pModel);
1298                     /* expose aircraft threat-level (to be used by other instruments,
1299                      * i.e. TCAS display) */
1300                     if (threatLevel==ThreatRA)
1301                         pModel->setIntValue("tcas/ra-sense", -threatDetector.getRASense());
1302                     pModel->setIntValue("tcas/threat-level", threatLevel);
1303                 }
1304             }
1305         }
1306         advisoryCoordinator.update(mode);
1307     }
1308     annunciator.update();
1309 }
1310
1311 /** Run a single self-test iteration. */
1312 void
1313 TCAS::selfTest(void)
1314 {
1315     annunciator.update();
1316     if (annunciator.isPlaying())
1317     {
1318         return;
1319     }
1320
1321     ResolutionAdvisory newAdvisory;
1322     newAdvisory.threatLevel = ThreatRA;
1323     newAdvisory.RA          = AdvisoryClear;
1324     newAdvisory.RAOption    = OptionNone;
1325     // TCAS audio is disabled below 500ft AGL
1326     threatDetector.setRadarAlt(501);
1327
1328     // trigger various advisories
1329     switch(selfTestStep)
1330     {
1331         case 0:
1332             newAdvisory.RA = AdvisoryIntrusion;
1333             newAdvisory.threatLevel = ThreatTA;
1334             break;
1335         case 1:
1336             newAdvisory.RA = AdvisoryClimb;
1337             break;
1338         case 2:
1339             newAdvisory.RA = AdvisoryClimb;
1340             newAdvisory.RAOption = OptionIncreaseClimb;
1341             break;
1342         case 3:
1343             newAdvisory.RA = AdvisoryClimb;
1344             newAdvisory.RAOption = OptionCrossingClimb;
1345             break;
1346         case 4:
1347             newAdvisory.RA = AdvisoryDescend;
1348             break;
1349         case 5:
1350             newAdvisory.RA = AdvisoryDescend;
1351             newAdvisory.RAOption = OptionIncreaseDescend;
1352             break;
1353         case 6:
1354             newAdvisory.RA = AdvisoryDescend;
1355             newAdvisory.RAOption = OptionCrossingDescent;
1356             break;
1357         case 7:
1358             newAdvisory.RA = AdvisoryAdjustVSpeed;
1359             break;
1360         case 8:
1361             newAdvisory.RA = AdvisoryMaintVSpeed;
1362             break;
1363         case 9:
1364             newAdvisory.RA = AdvisoryMonitorVSpeed;
1365             break;
1366         case 10:
1367             newAdvisory.threatLevel = ThreatNone;
1368             newAdvisory.RA = AdvisoryClear;
1369             break;
1370         case 11:
1371             annunciator.test(true);
1372             selfTestStep+=2;
1373             return;
1374         default:
1375             nodeSelfTest->setBoolValue(false);
1376             selfTestStep = 0;
1377             return;
1378     }
1379
1380     advisoryCoordinator.add(newAdvisory);
1381     advisoryCoordinator.update(SwitchAuto);
1382
1383     selfTestStep++;
1384 }
1385
1386 ///////////////////////////////////////////////////////////////////////////////
1387 // TCAS::Tracker //////////////////////////////////////////////////////////////
1388 ///////////////////////////////////////////////////////////////////////////////
1389
1390 TCAS::Tracker::Tracker(TCAS* _tcas) :
1391     tcas(_tcas),
1392     currentTime(0),
1393     haveTargets(false),
1394     newTargets(false)
1395 {
1396     targets.clear();
1397 }
1398
1399 void
1400 TCAS::Tracker::update(void)
1401 {
1402     currentTime = globals->get_sim_time_sec();
1403     newTargets = false;
1404
1405     if (haveTargets)
1406     {
1407         // remove outdated targets
1408         TrackerTargets::iterator it = targets.begin();
1409         while (it != targets.end())
1410         {
1411             TrackerTarget* pTarget = it->second;
1412             if (currentTime - pTarget->TAtimestamp > 10.0)
1413             {
1414                 TrackerTargets::iterator temp = it;
1415                 ++it;
1416 #ifdef FEATURE_TCAS_DEBUG_TRACKER
1417                 printf("target %s no longer a TA threat.\n",temp->first.c_str());
1418 #endif
1419                 targets.erase(temp->first);
1420                 delete pTarget;
1421                 pTarget = NULL;
1422             }
1423             else
1424             {
1425                 if ((pTarget->threatLevel == ThreatRA)&&
1426                     (currentTime - pTarget->RAtimestamp > 7.0))
1427                 {
1428                     pTarget->threatLevel = ThreatTA;
1429 #ifdef FEATURE_TCAS_DEBUG_TRACKER
1430                     printf("target %s no longer an RA threat.\n",it->first.c_str());
1431 #endif
1432                 }
1433                 ++it;
1434             }
1435         }
1436         haveTargets = !targets.empty();
1437     }
1438 }
1439
1440 void
1441 TCAS::Tracker::add(const string callsign, int detectedLevel)
1442 {
1443     TrackerTarget* pTarget = NULL;
1444     if (haveTargets)
1445     {
1446         TrackerTargets::iterator it = targets.find(callsign);
1447         if (it != targets.end())
1448         {
1449             pTarget = it->second;
1450         }
1451     }
1452
1453     if (!pTarget)
1454     {
1455         pTarget = new TrackerTarget();
1456         pTarget->TAtimestamp = 0;
1457         pTarget->RAtimestamp = 0;
1458         pTarget->threatLevel = 0;
1459         newTargets = true;
1460         targets[callsign] = pTarget;
1461 #ifdef FEATURE_TCAS_DEBUG_TRACKER
1462         printf("new target: %s, level: %i\n",callsign.c_str(),detectedLevel);
1463 #endif
1464     }
1465
1466     if (detectedLevel > pTarget->threatLevel)
1467         pTarget->threatLevel = detectedLevel;
1468
1469     if (detectedLevel >= ThreatTA)
1470         pTarget->TAtimestamp = currentTime;
1471
1472     if (detectedLevel >= ThreatRA)
1473         pTarget->RAtimestamp = currentTime;
1474
1475     haveTargets = true;
1476 }
1477
1478 bool
1479 TCAS::Tracker::_isTracked(string callsign)
1480 {
1481     return targets.find(callsign) != targets.end();
1482 }
1483
1484 int
1485 TCAS::Tracker::getThreatLevel(string callsign)
1486 {
1487     TrackerTargets::iterator it = targets.find(callsign);
1488     if (it != targets.end())
1489         return it->second->threatLevel;
1490     else
1491         return 0;
1492 }