1 // dme.cxx - distance-measuring equipment.
2 // Written by David Megginson, started 2003.
4 // This file is in the Public Domain and comes with no warranty.
10 #include <simgear/compiler.h>
11 #include <simgear/sg_inlines.h>
12 #include <simgear/math/sg_geodesy.hxx>
13 #include <simgear/math/sg_random.h>
15 #include <Main/fg_props.hxx>
16 #include <Navaids/navlist.hxx>
17 #include <Sound/audioident.hxx>
24 * Start by calculating the radar horizon based on the elevation
25 * difference, then clamp to the maximum, then add a fudge for
26 * borderline reception.
29 adjust_range (double transmitter_elevation_ft, double aircraft_altitude_ft,
32 double delta_elevation_ft =
33 fabs(aircraft_altitude_ft - transmitter_elevation_ft);
34 double range_nm = 1.23 * sqrt(delta_elevation_ft);
35 if (range_nm > max_range_nm)
36 range_nm = max_range_nm;
37 else if (range_nm < 20.0)
39 double rand = sg_random();
40 return range_nm + (range_nm * rand * rand);
45 class DMEFilter : public FGNavList::TypeFilter
49 TypeFilter(FGPositioned::DME),
50 _locEnabled(fgGetBool("/sim/realism/dme-fallback-to-loc", true))
53 _mintype = FGPositioned::ILS;
57 virtual bool pass(FGPositioned* pos) const
59 switch (pos->type()) {
60 case FGPositioned::DME: return true;
61 case FGPositioned::ILS:
62 case FGPositioned::LOC: return _locEnabled;
63 default: return false;
68 const bool _locEnabled;
71 } // of anonymous namespace
74 DME::DME ( SGPropertyNode *node )
75 : _last_distance_nm(0),
76 _last_frequency_mhz(-1),
77 _time_before_search_sec(0),
79 _name(node->getStringValue("name", "dme")),
80 _num(node->getIntValue("number", 0)),
94 branch = "/instrumentation/" + _name;
96 SGPropertyNode *node = fgGetNode(branch.c_str(), _num, true );
98 _serviceable_node = node->getChild("serviceable", 0, true);
99 _electrical_node = fgGetNode("/systems/electrical/outputs/dme", true);
100 SGPropertyNode *fnode = node->getChild("frequencies", 0, true);
101 _source_node = fnode->getChild("source", 0, true);
102 _frequency_node = fnode->getChild("selected-mhz", 0, true);
103 _in_range_node = node->getChild("in-range", 0, true);
104 _distance_node = node->getChild("indicated-distance-nm", 0, true);
105 _speed_node = node->getChild("indicated-ground-speed-kt", 0, true);
106 _time_node = node->getChild("indicated-time-min", 0, true);
108 double d = node->getDoubleValue( "volume", 1.0 );
109 _volume_node = node->getChild("volume", 0, true);
110 _volume_node->setDoubleValue( d );
112 bool b = node->getBoolValue( "ident", false );
113 _ident_btn_node = node->getChild("ident", 0, true);
114 _ident_btn_node->setBoolValue( b );
116 std::ostringstream temp;
117 temp << _name << "-ident-" << _num;
118 if( NULL == _audioIdent )
119 _audioIdent = new DMEAudioIdent( temp.str() );
128 _time_before_search_sec = 0;
132 DME::update (double delta_time_sec)
134 if( delta_time_sec < SGLimitsd::min() )
137 // Figure out the source
138 const char * source = _source_node->getStringValue();
139 if (source[0] == '\0') {
141 branch = "/instrumentation/" + _name + "/frequencies/selected-mhz";
142 _source_node->setStringValue(branch.c_str());
143 source = _source_node->getStringValue();
147 double frequency_mhz = fgGetDouble(source, 108.0);
148 if (frequency_mhz != _last_frequency_mhz) {
149 _time_before_search_sec = 0;
150 _last_frequency_mhz = frequency_mhz;
152 _frequency_node->setDoubleValue(frequency_mhz);
154 // Get the aircraft position
155 // On timeout, scan again
156 _time_before_search_sec -= delta_time_sec;
157 if (_time_before_search_sec < 0) {
158 _time_before_search_sec = 1.0;
160 SGGeod pos(globals->get_aircraft_position());
162 _navrecord = FGNavList::findByFreq(frequency_mhz, pos, &filter);
165 // If it's off, don't bother.
166 if (!_serviceable_node->getBoolValue() ||
167 !_electrical_node->getBoolValue() ||
168 NULL == _navrecord ) {
169 _last_distance_nm = 0;
170 _in_range_node->setBoolValue(false);
171 _distance_node->setDoubleValue(0);
172 _speed_node->setDoubleValue(0);
173 _time_node->setDoubleValue(0);
174 _audioIdent->setIdent("", 0.0 );
178 // Calculate the distance to the transmitter
179 SGVec3d location = SGVec3d::fromGeod(globals->get_aircraft_position());
181 double distance_nm = dist(_navrecord->cart(), location) * SG_METER_TO_NM;
183 double range_nm = adjust_range(_navrecord->get_elev_ft(),
184 globals->get_aircraft_position().getElevationFt(),
185 _navrecord->get_range());
187 if (distance_nm <= range_nm) {
188 double volume = _volume_node->getDoubleValue();
189 if( false == _ident_btn_node->getBoolValue() )
192 _audioIdent->setIdent(_navrecord->ident(), volume );
194 double speed_kt = (fabs(distance_nm - _last_distance_nm) *
195 ((1 / delta_time_sec) * 3600.0));
196 _last_distance_nm = distance_nm;
198 _in_range_node->setBoolValue(true);
199 double tmp_dist = distance_nm - _navrecord->get_multiuse();
200 if ( tmp_dist < 0.0 ) {
203 _distance_node->setDoubleValue( tmp_dist );
204 _speed_node->setDoubleValue(speed_kt);
205 if (SGLimitsd::min() < fabs(speed_kt))
206 _time_node->setDoubleValue(distance_nm/speed_kt*60.0);
209 _last_distance_nm = 0;
210 _in_range_node->setBoolValue(false);
211 _distance_node->setDoubleValue(0);
212 _speed_node->setDoubleValue(0);
213 _time_node->setDoubleValue(0);
214 _audioIdent->setIdent("", 0.0 );
217 _audioIdent->update( delta_time_sec );