1 // adf.cxx - distance-measuring equipment.
2 // Written by David Megginson, started 2003.
4 // This file is in the Public Domain and comes with no warranty.
6 #include <simgear/compiler.h>
7 #include <simgear/math/sg_geodesy.hxx>
8 #include <simgear/math/sg_random.h>
10 #include <Main/fg_props.hxx>
11 #include <Main/util.hxx>
12 #include <Navaids/navlist.hxx>
17 // Use a bigger number to be more responsive, or a smaller number
18 // to be more sluggish.
19 #define RESPONSIVENESS 0.5
23 * Fiddle with the reception range a bit.
25 * TODO: better reception at night (??).
28 adjust_range (double transmitter_elevation_ft, double aircraft_altitude_ft,
31 double delta_elevation_ft =
32 aircraft_altitude_ft - transmitter_elevation_ft;
33 double range_nm = max_range_nm;
35 // kludge slightly better reception at
37 if (delta_elevation_ft < 0)
38 delta_elevation_ft = 200;
39 if (delta_elevation_ft <= 1000)
40 range_nm *= sqrt(delta_elevation_ft / 1000);
41 else if (delta_elevation_ft >= 5000)
42 range_nm *= sqrt(delta_elevation_ft / 5000);
43 if (range_nm >= max_range_nm * 3)
44 range_nm = max_range_nm * 3;
46 double rand = sg_random();
47 return range_nm + (range_nm * rand * rand);
52 : _last_frequency_khz(-1),
53 _time_before_search_sec(0),
54 _transmitter_valid(false),
55 _transmitter_elevation_ft(0),
56 _transmitter_range_nm(0)
67 _longitude_node = fgGetNode("/position/longitude-deg", true);
68 _latitude_node = fgGetNode("/position/latitude-deg", true);
69 _altitude_node = fgGetNode("/position/altitude-ft", true);
70 _heading_node = fgGetNode("/orientation/heading-deg", true);
71 _serviceable_node = fgGetNode("/instrumentation/adf/serviceable", true);
72 _error_node = fgGetNode("/instrumentation/adf/error-deg", true);
73 _electrical_node = fgGetNode("/systems/electrical/outputs/adf", true);
75 fgGetNode("/instrumentation/adf/frequencies/selected-khz", true);
76 _mode_node = fgGetNode("/instrumentation/adf/mode", true);
78 _in_range_node = fgGetNode("/instrumentation/adf/in-range", true);
80 fgGetNode("/instrumentation/adf/indicated-bearing-deg", true);
81 _ident_node = fgGetNode("/instrumentation/adf/ident", true);
85 ADF::update (double delta_time_sec)
87 // If it's off, don't waste any time.
88 if (!_electrical_node->getBoolValue() ||
89 !_serviceable_node->getBoolValue()) {
90 set_bearing(delta_time_sec, 90);
91 _ident_node->setStringValue("");
96 int frequency_khz = _frequency_node->getIntValue();
97 if (frequency_khz != _last_frequency_khz) {
98 _time_before_search_sec = 0;
99 _last_frequency_khz = frequency_khz;
102 // Get the aircraft position
103 double longitude_deg = _longitude_node->getDoubleValue();
104 double latitude_deg = _latitude_node->getDoubleValue();
105 double altitude_m = _altitude_node->getDoubleValue();
107 double longitude_rad = longitude_deg * SGD_DEGREES_TO_RADIANS;
108 double latitude_rad = latitude_deg * SGD_DEGREES_TO_RADIANS;
110 // On timeout, scan again
111 _time_before_search_sec -= delta_time_sec;
112 if (_time_before_search_sec < 0)
113 search(frequency_khz, longitude_rad, latitude_rad, altitude_m);
115 // If it's off, don't bother.
116 string mode = _mode_node->getStringValue();
117 if (!_transmitter_valid || (mode != "bfo" && mode != "adf"))
119 set_bearing(delta_time_sec, 90);
120 _ident_node->setStringValue("");
124 // Calculate the bearing to the transmitter
126 sgGeodToCart(Point3D(longitude_rad, latitude_rad, altitude_m));
128 double distance_nm = _transmitter.distance3D(location) * SG_METER_TO_NM;
129 double range_nm = adjust_range(_transmitter_elevation_ft,
130 altitude_m * SG_METER_TO_FEET,
131 _transmitter_range_nm);
132 if (distance_nm <= range_nm) {
134 double bearing, az2, s;
135 double heading = _heading_node->getDoubleValue();
137 geo_inverse_wgs_84(altitude_m,
140 _transmitter_lat_deg,
141 _transmitter_lon_deg,
143 _in_range_node->setBoolValue(true);
148 set_bearing(delta_time_sec, bearing);
150 _in_range_node->setBoolValue(false);
151 set_bearing(delta_time_sec, 90);
152 _ident_node->setStringValue("");
157 ADF::search (double frequency_khz, double longitude_rad,
158 double latitude_rad, double altitude_m)
163 _time_before_search_sec = 1.0;
165 // try the ILS list first
167 current_navlist->findByFreq(frequency_khz, longitude_rad,
168 latitude_rad, altitude_m);
171 _transmitter_valid = true;
172 ident = nav->get_trans_ident();
173 if (ident !=_last_ident) {
174 _transmitter_lon_deg = nav->get_lon();
175 _transmitter_lat_deg = nav->get_lat();
176 _transmitter = Point3D(nav->get_x(), nav->get_y(), nav->get_z());
177 _transmitter_elevation_ft = nav->get_elev_ft();
178 _transmitter_range_nm = nav->get_range();
181 _transmitter_valid = false;
184 _ident_node->setStringValue(ident.c_str());
188 ADF::set_bearing (double dt, double bearing_deg)
190 double old_bearing_deg = _bearing_node->getDoubleValue();
192 bearing_deg += _error_node->getDoubleValue();
194 while ((bearing_deg - old_bearing_deg) >= 180)
195 old_bearing_deg += 360;
196 while ((bearing_deg - old_bearing_deg) <= -180)
197 old_bearing_deg -= 360;
200 fgGetLowPass(old_bearing_deg, bearing_deg, dt * RESPONSIVENESS);
202 _bearing_node->setDoubleValue(bearing_deg);