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>
14 #include <simgear/sound/sample_group.hxx>
16 #include <Main/fg_props.hxx>
17 #include <Navaids/navlist.hxx>
18 #include <Sound/audioident.hxx>
28 * Start by calculating the radar horizon based on the elevation
29 * difference, then clamp to the maximum, then add a fudge for
30 * borderline reception.
33 adjust_range (double transmitter_elevation_ft, double aircraft_altitude_ft,
36 double delta_elevation_ft =
37 fabs(aircraft_altitude_ft - transmitter_elevation_ft);
38 double range_nm = 1.23 * sqrt(delta_elevation_ft);
39 if (range_nm > max_range_nm)
40 range_nm = max_range_nm;
41 else if (range_nm < 20.0)
43 double rand = sg_random();
44 return range_nm + (range_nm * rand * rand);
49 class DMEFilter : public FGNavList::TypeFilter
53 TypeFilter(FGPositioned::DME),
54 _locEnabled(fgGetBool("/sim/realism/dme-fallback-to-loc", true))
57 _mintype = FGPositioned::ILS;
61 virtual bool pass(FGPositioned* pos) const
63 switch (pos->type()) {
64 case FGPositioned::DME: return true;
65 case FGPositioned::ILS:
66 case FGPositioned::LOC: return _locEnabled;
67 default: return false;
72 const bool _locEnabled;
75 } // of anonymous namespace
78 DME::DME ( SGPropertyNode *node )
79 : _last_distance_nm(0),
80 _last_frequency_mhz(-1),
81 _time_before_search_sec(0),
83 _name(node->getStringValue("name", "dme")),
84 _num(node->getIntValue("number", 0)),
98 branch = "/instrumentation/" + _name;
100 SGPropertyNode *node = fgGetNode(branch.c_str(), _num, true );
102 _serviceable_node = node->getChild("serviceable", 0, true);
103 _electrical_node = fgGetNode("/systems/electrical/outputs/dme", true);
104 SGPropertyNode *fnode = node->getChild("frequencies", 0, true);
105 _source_node = fnode->getChild("source", 0, true);
106 _frequency_node = fnode->getChild("selected-mhz", 0, true);
107 _in_range_node = node->getChild("in-range", 0, true);
108 _distance_node = node->getChild("indicated-distance-nm", 0, true);
109 _speed_node = node->getChild("indicated-ground-speed-kt", 0, true);
110 _time_node = node->getChild("indicated-time-min", 0, true);
112 double d = node->getDoubleValue( "volume", 1.0 );
113 _volume_node = node->getChild("volume", 0, true);
114 _volume_node->setDoubleValue( d );
116 bool b = node->getBoolValue( "ident", false );
117 _ident_btn_node = node->getChild("ident", 0, true);
118 _ident_btn_node->setBoolValue( b );
120 SGPropertyNode *subnode = node->getChild("KDI572-574", 0, true);
122 _distance_string = subnode->getChild("nm",0, true);
123 _distance_string->setStringValue("---");
124 _speed_string = subnode->getChild("kt", 0, true);
125 _speed_string->setStringValue("---");
126 _time_string = subnode->getChild("min",0, true);
127 _time_string->setStringValue("--");
129 std::ostringstream temp;
130 temp << _name << "-ident-" << _num;
131 if( NULL == _audioIdent )
132 _audioIdent = new DMEAudioIdent( temp.str() );
141 _time_before_search_sec = 0;
145 DME::update (double delta_time_sec)
147 if( delta_time_sec < SGLimitsd::min() )
150 // Figure out the source
151 const char * source = _source_node->getStringValue();
152 if (source[0] == '\0') {
154 branch = "/instrumentation/" + _name + "/frequencies/selected-mhz";
155 _source_node->setStringValue(branch.c_str());
156 source = _source_node->getStringValue();
160 double frequency_mhz = fgGetDouble(source, 108.0);
161 if (frequency_mhz != _last_frequency_mhz) {
162 _time_before_search_sec = 0;
163 _last_frequency_mhz = frequency_mhz;
165 _frequency_node->setDoubleValue(frequency_mhz);
167 // Get the aircraft position
168 // On timeout, scan again
169 _time_before_search_sec -= delta_time_sec;
170 if (_time_before_search_sec < 0) {
171 _time_before_search_sec = 1.0;
173 SGGeod pos(globals->get_aircraft_position());
175 _navrecord = FGNavList::findByFreq(frequency_mhz, pos, &filter);
179 // If it's off, don't bother.
180 if (!_serviceable_node->getBoolValue() ||
181 !_electrical_node->getBoolValue()){
182 _last_distance_nm = 0;
183 _in_range_node->setBoolValue(false);
184 _distance_node->setDoubleValue(0);
185 _speed_node->setDoubleValue(0);
186 _time_node->setDoubleValue(0);
187 _audioIdent->setIdent("", 0.0 );
188 _distance_string->setStringValue("");
189 _speed_string->setStringValue("");
190 _time_string->setStringValue("");
193 // If it's on, but invalid source,don't bother.
194 if (NULL == _navrecord ){
195 _distance_string->setStringValue("---");
196 _speed_string->setStringValue("---");
197 _time_string->setStringValue("--");
200 // Calculate the distance to the transmitter
201 double distance_nm = dist(_navrecord->cart(),
202 globals->get_aircraft_position_cart()) * SG_METER_TO_NM;
204 double range_nm = adjust_range(_navrecord->get_elev_ft(),
205 globals->get_aircraft_position().getElevationFt(),
206 _navrecord->get_range());
208 if (distance_nm <= range_nm) {
209 double volume = _volume_node->getDoubleValue();
210 if( false == _ident_btn_node->getBoolValue() )
213 _audioIdent->setIdent(_navrecord->ident(), volume );
215 double speed_kt = (fabs(distance_nm - _last_distance_nm) *
216 ((1 / delta_time_sec) * 3600.0));
217 _last_distance_nm = distance_nm;
219 _in_range_node->setBoolValue(true);
220 double tmp_dist = distance_nm - _navrecord->get_multiuse();
221 if ( tmp_dist < 0.0 ) {
224 _distance_node->setDoubleValue( tmp_dist );
225 if ( tmp_dist >389 ) tmp_dist = 389;
226 if ( tmp_dist >= 100.0) {
227 snprintf ( tmp,16,"%3.0f",tmp_dist);
229 snprintf ( tmp,16,"%2.1f",tmp_dist);
231 _distance_string->setStringValue(tmp);
233 _speed_node->setDoubleValue(speed_kt);
234 double spd = speed_kt;
236 snprintf ( tmp,16,"%3.0f",spd);
237 _speed_string->setStringValue(tmp);
240 if (SGLimitsd::min() < fabs(speed_kt)){
241 double tm = distance_nm/speed_kt*60.0;
242 _time_node->setDoubleValue(tm);
244 snprintf ( tmp,16,"%2.0f",tm);
245 _time_string->setStringValue(tmp);
249 _last_distance_nm = 0;
250 _in_range_node->setBoolValue(false);
251 _distance_node->setDoubleValue(0);
252 _distance_string->setStringValue("---");
253 _speed_node->setDoubleValue(0);
254 _speed_string->setStringValue("---");
255 _time_node->setDoubleValue(0);
256 _time_string->setStringValue("--");
257 _audioIdent->setIdent("", 0.0 );
259 _audioIdent->update( delta_time_sec );