#include #include #include "tacan.hxx" /** * Adjust the range. * * Start by calculating the radar horizon based on the elevation * difference, then clamp to the maximum, then add a fudge for * borderline reception. */ static double adjust_range( double station_elevation_ft, double aircraft_altitude_ft, double max_range_nm ) { // See http://en.wikipedia.org/wiki/Line-of-sight_propagation for approximate // line-of-sight distance to the horizon double range_nm = 0; if( station_elevation_ft > 5 ) range_nm += 1.23 * sqrt(station_elevation_ft); if( aircraft_altitude_ft > 5 ) range_nm += 1.23 * sqrt(aircraft_altitude_ft); return std::max(20., std::min(range_nm, max_range_nm)) * (1 + SGMiscd::pow<2>(0.3 * sg_random())); } //------------------------------------------------------------------------------ TACAN::TACAN( SGPropertyNode *node ): _name(node->getStringValue("name", "tacan")), _num(node->getIntValue("number", 0)), _was_disabled(true), _new_frequency(false), _channel("0000"), _last_distance_nm(0), _frequency_mhz(-1), _time_before_search_sec(0), _listener_active(0) { } //------------------------------------------------------------------------------ TACAN::~TACAN() { } //------------------------------------------------------------------------------ void TACAN::init() { std::string branch = "/instrumentation/" + _name; SGPropertyNode *node = fgGetNode(branch.c_str(), _num, true ); _serviceable_node = node->getChild("serviceable", 0, true); _ident_node = node->getChild("ident", 0, true); SGPropertyNode *fnode = node->getChild("frequencies", 0, true); _frequency_node = fnode->getChild("selected-mhz", 0, true); _channel_in0_node = fnode->getChild("selected-channel", 0, true); _channel_in1_node = fnode->getChild("selected-channel", 1, true); _channel_in2_node = fnode->getChild("selected-channel", 2, true); _channel_in3_node = fnode->getChild("selected-channel", 3, true); _channel_in4_node = fnode->getChild("selected-channel", 4, true); _in_range_node = node->getChild("in-range", 0, true); _distance_node = node->getChild("indicated-distance-nm", 0, true); _speed_node = node->getChild("indicated-ground-speed-kt", 0, true); _time_node = node->getChild("indicated-time-min", 0, true); _name_node = node->getChild("name", 0, true); _bearing_node = node->getChild("indicated-bearing-true-deg", 0, true); SGPropertyNode *dnode = node->getChild("display", 0, true); _x_shift_node = dnode->getChild("x-shift", 0, true); _y_shift_node = dnode->getChild("y-shift", 0, true); _channel_node = dnode->getChild("channel", 0, true); _heading_node = fgGetNode("/orientation/heading-deg", true); _electrical_node = fgGetNode("/systems/electrical/outputs/tacan", true); // Add/trigger change listener after creating all nodes _channel_in0_node->addChangeListener(this); _channel_in1_node->addChangeListener(this); _channel_in2_node->addChangeListener(this); _channel_in3_node->addChangeListener(this); _channel_in4_node->addChangeListener(this, true); disabled(true); } //------------------------------------------------------------------------------ void TACAN::reinit() { _time_before_search_sec = 0; } //------------------------------------------------------------------------------ void TACAN::update(double delta_time_sec) { // don't do anything when paused if( delta_time_sec == 0 ) return; if( !_serviceable_node->getBoolValue() || !_electrical_node->getBoolValue() ) return disabled(); SGGeod pos(globals->get_aircraft_position()); // On timeout, scan again _time_before_search_sec -= delta_time_sec; if ((_time_before_search_sec < 0 || _new_frequency) && _frequency_mhz >= 0) search(_frequency_mhz, pos); if( !_active_station || !_active_station->get_serviceable() ) return disabled(); const SGGeod& nav_pos = _active_station->geod(); // Calculate the bearing and range of the station from the aircraft double az = 0; double bearing = 0; double distance = SGLimitsd::max(); if( !SGGeodesy::inverse(pos, nav_pos, bearing, az, distance) ) return disabled(); // Increase distance due to difference in altitude distance = sqrt( SGMiscd::pow<2>(distance) + SGMiscd::pow<2>(pos.getElevationM() - nav_pos.getElevationM()) ); double distance_nm = distance * SG_METER_TO_NM; double range_nm = adjust_range( nav_pos.getElevationFt(), pos.getElevationFt(), _active_station->get_range() ); if( distance_nm > range_nm ) return disabled(); //// calculate look left/right to target, without yaw correction // double horiz_offset = bearing - heading; // // if (horiz_offset > 180.0) horiz_offset -= 360.0; // if (horiz_offset < -180.0) horiz_offset += 360.0; //// now correct look left/right for yaw // horiz_offset += yaw; // use the bearing for a plan position indicator display double horiz_offset = bearing; // calculate values for radar display double y_shift = distance_nm * cos(horiz_offset * SG_DEGREES_TO_RADIANS); double x_shift = distance_nm * sin(horiz_offset * SG_DEGREES_TO_RADIANS); // TODO probably not the best way to do this (especially with mobile stations) double speed_kt = fabs(distance_nm - _last_distance_nm) * (3600 / delta_time_sec); _speed_node->setDoubleValue(speed_kt); _last_distance_nm = distance_nm; double bias = _active_station->get_multiuse(); _distance_node->setDoubleValue( SGMiscd::max(0.0, distance_nm - bias) ); _time_node->setDoubleValue(speed_kt > 0 ? (distance_nm/speed_kt*60.0) : 0); _bearing_node->setDoubleValue(bearing); _x_shift_node->setDoubleValue(x_shift); _y_shift_node->setDoubleValue(y_shift); _name_node->setStringValue(_active_station->name()); _ident_node->setStringValue(_active_station->ident()); _in_range_node->setBoolValue(true); _was_disabled = false; } //------------------------------------------------------------------------------ void TACAN::disabled(bool force) { if( _was_disabled && !force ) return; _last_distance_nm = 0; _in_range_node->setBoolValue(false); _distance_node->setDoubleValue(0); _speed_node->setDoubleValue(0); _time_node->setDoubleValue(0); _bearing_node->setDoubleValue(0); _x_shift_node->setDoubleValue(0); _y_shift_node->setDoubleValue(0); _name_node->setStringValue(""); _ident_node->setStringValue(""); _was_disabled = true; } //------------------------------------------------------------------------------ void TACAN::search (double frequency_mhz,const SGGeod& pos) { // reset search time _time_before_search_sec = 5; // Get first matching mobile station (carriers/tankers/etc.) // TODO do we need to check for mobile stations with same frequency? Currently // the distance is not taken into account. FGNavRecordRef mobile_tacan = FGNavList::findByFreq(frequency_mhz, FGNavList::mobileTacanFilter()); double mobile_dist = (mobile_tacan && mobile_tacan->get_serviceable()) ? SGGeodesy::distanceM(pos, mobile_tacan->geod()) : SGLimitsd::max(); // No get nearest TACAN/VORTAC FGNavRecordRef tacan = FGNavList::findByFreq(frequency_mhz, pos, FGNavList::tacanFilter()); double tacan_dist = tacan ? SGGeodesy::distanceM(pos, tacan->geod()) : SGLimitsd::max(); // Select nearer station as active // TODO do we need to take more care of stations with same frequency? _active_station = mobile_dist < tacan_dist ? mobile_tacan : tacan; } //------------------------------------------------------------------------------ double TACAN::searchChannel(const std::string& channel) { FGTACANRecord *freq = globals->get_channellist()->findByChannel(channel); if( !freq ) { SG_LOG(SG_INSTR, SG_DEBUG, "Invalid TACAN channel: " << channel); return 0; } double frequency_khz = freq->get_freq(); if(frequency_khz < 9620 || frequency_khz > 121300) { SG_LOG ( SG_INSTR, SG_DEBUG, "TACAN frequency out of range: " << channel << ": " << frequency_khz << "kHz" ); return 0; } return frequency_khz/100; } /* * Listener callback. Maintains channel input properties, * searches new channel frequency, updates _channel and * _frequency and sets boolean _new_frequency appropriately. */ void TACAN::valueChanged(SGPropertyNode *prop) { if (_listener_active) return; _listener_active++; int index = prop->getIndex(); std::string channel = _channel; if (index) { // channel digit or X/Y input int c; if (isdigit(c = _channel_in1_node->getStringValue()[0])) channel[0] = c; if (isdigit(c = _channel_in2_node->getStringValue()[0])) channel[1] = c; if (isdigit(c = _channel_in3_node->getStringValue()[0])) channel[2] = c; c = _channel_in4_node->getStringValue()[0]; if (c == 'X' || c == 'Y') channel[3] = c; } else { // channel number input unsigned int f = prop->getIntValue(); if (f >= 1 && f <= 126) { channel[0] = '0' + (f / 100) % 10; channel[1] = '0' + (f / 10) % 10; channel[2] = '0' + f % 10; } } if (channel != _channel) { SG_LOG(SG_INSTR, SG_DEBUG, "new channel " << channel); // write back result _channel_in0_node->setIntValue((channel[0] - '0') * 100 + (channel[1] - '0') * 10 + (channel[2] - '0')); char s[2] = "0"; s[0] = channel[0], _channel_in1_node->setStringValue(s); s[0] = channel[1], _channel_in2_node->setStringValue(s); s[0] = channel[2], _channel_in3_node->setStringValue(s); s[0] = channel[3], _channel_in4_node->setStringValue(s); // search channel frequency double freq = searchChannel(channel); if (freq != _frequency_mhz) { SG_LOG(SG_INSTR, SG_DEBUG, "new frequency " << freq); _frequency_node->setDoubleValue(freq); _frequency_mhz = freq; _new_frequency = true; } _channel = channel; _channel_node->setStringValue(_channel); _time_before_search_sec = 0; } _listener_active--; } // end of TACAN.cxx