1 // radio.cxx -- implementation of FGRadio
2 // Class to manage radio propagation using the ITM model
3 // Written by Adrian Musceac YO8RZZ, started August 2011.
5 // This program is free software; you can redistribute it and/or
6 // modify it under the terms of the GNU General Public License as
7 // published by the Free Software Foundation; either version 2 of the
8 // License, or (at your option) any later version.
10 // This program is distributed in the hope that it will be useful, but
11 // WITHOUT ANY WARRANTY; without even the implied warranty of
12 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 // General Public License for more details.
15 // You should have received a copy of the GNU General Public License
16 // along with this program; if not, write to the Free Software
17 // Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
30 #include <simgear/scene/material/mat.hxx>
31 #include <Scenery/scenery.hxx>
32 #include <boost/scoped_array.hpp>
34 #define WITH_POINT_TO_POINT 1
38 FGRadioTransmission::FGRadioTransmission() {
41 _receiver_sensitivity = -105.0; // typical AM receiver sensitivity seems to be 0.8 microVolt at 12dB SINAD or less
43 /** AM transmitter power in dBm.
44 * Typical output powers for ATC ground equipment, VHF-UHF:
45 * 40 dBm - 10 W (ground, clearance)
46 * 44 dBm - 20 W (tower)
47 * 47 dBm - 50 W (center, sectors)
48 * 50 dBm - 100 W (center, sectors)
49 * 53 dBm - 200 W (sectors, on directional arrays)
51 _transmitter_power = 43.0;
53 _tx_antenna_height = 2.0; // TX antenna height above ground level
55 _rx_antenna_height = 2.0; // RX antenna height above ground level
58 _rx_antenna_gain = 1.0; // maximum antenna gain expressed in dBi
59 _tx_antenna_gain = 1.0;
61 _rx_line_losses = 2.0; // to be configured for each station
62 _tx_line_losses = 2.0;
64 _polarization = 1; // default vertical
66 _propagation_model = 2;
68 _root_node = fgGetNode("sim/radio", true);
69 _terrain_sampling_distance = _root_node->getDoubleValue("sampling-distance", 90.0); // regular SRTM is 90 meters
74 FGRadioTransmission::~FGRadioTransmission()
79 double FGRadioTransmission::getFrequency(int radio) {
83 freq = fgGetDouble("/instrumentation/comm[0]/frequencies/selected-mhz");
86 freq = fgGetDouble("/instrumentation/comm[1]/frequencies/selected-mhz");
89 freq = fgGetDouble("/instrumentation/comm[0]/frequencies/selected-mhz");
96 void FGRadioTransmission::receiveChat(SGGeod tx_pos, double freq, string text, int ground_to_air) {
101 double FGRadioTransmission::receiveNav(SGGeod tx_pos, double freq, int transmission_type) {
103 // typical VOR/LOC transmitter power appears to be 100 - 200 Watt i.e 50 - 53 dBm
104 // vor/loc typical sensitivity between -107 and -101 dBm
105 // glideslope sensitivity between -85 and -81 dBm
106 if ( _propagation_model == 1) {
107 return LOS_calculate_attenuation(tx_pos, freq, 1);
109 else if ( _propagation_model == 2) {
110 return ITM_calculate_attenuation(tx_pos, freq, 1);
118 double FGRadioTransmission::receiveBeacon(SGGeod &tx_pos, double heading, double pitch) {
120 // these properties should be set by an instrument
121 _receiver_sensitivity = _root_node->getDoubleValue("station[0]/rx-sensitivity", _receiver_sensitivity);
122 _transmitter_power = watt_to_dbm(_root_node->getDoubleValue("station[0]/tx-power-watt", _transmitter_power));
123 _polarization = _root_node->getIntValue("station[0]/polarization", 1);
124 _tx_antenna_height += _root_node->getDoubleValue("station[0]/tx-antenna-height", 0);
125 _rx_antenna_height += _root_node->getDoubleValue("station[0]/rx-antenna-height", 0);
126 _tx_antenna_gain += _root_node->getDoubleValue("station[0]/tx-antenna-gain", 0);
127 _rx_antenna_gain += _root_node->getDoubleValue("station[0]/rx-antenna-gain", 0);
129 double freq = _root_node->getDoubleValue("station[0]/frequency", 144.8); // by default stay in the ham 2 meter band
131 double comm1 = getFrequency(1);
132 double comm2 = getFrequency(2);
133 if ( !(fabs(freq - comm1) <= 0.0001) && !(fabs(freq - comm2) <= 0.0001) ) {
137 double signal = ITM_calculate_attenuation(tx_pos, freq, 1);
144 void FGRadioTransmission::receiveATC(SGGeod tx_pos, double freq, string text, int ground_to_air) {
146 // adjust some default parameters in case the ATC code does not set them
147 if(ground_to_air == 1) {
148 _transmitter_power += 4.0;
149 _tx_antenna_height += 30.0;
150 _tx_antenna_gain += 2.0;
153 double comm1 = getFrequency(1);
154 double comm2 = getFrequency(2);
155 if ( !(fabs(freq - comm1) <= 0.0001) && !(fabs(freq - comm2) <= 0.0001) ) {
160 if ( _propagation_model == 0) { // skip propagation routines entirely
161 fgSetString("/sim/messages/atc", text.c_str());
163 else if ( _propagation_model == 1 ) { // Use free-space, round earth
165 double signal = LOS_calculate_attenuation(tx_pos, freq, ground_to_air);
170 fgSetString("/sim/messages/atc", text.c_str());
173 else if ( _propagation_model == 2 ) { // Use ITM propagation model
175 double signal = ITM_calculate_attenuation(tx_pos, freq, ground_to_air);
179 if ((signal > 0.0) && (signal < 12.0)) {
180 /** for low SNR values need a way to make the conversation
181 * hard to understand but audible
182 * in the real world, the receiver AGC fails to capture the slope
183 * and the signal, due to being amplitude modulated, decreases volume after demodulation
184 * the workaround below is more akin to what would happen on a FM transmission
185 * therefore the correct way would be to work on the volume
188 string hash_noise = " ";
189 int reps = (int) (fabs(floor(signal - 11.0)) * 2);
190 int t_size = text.size();
191 for (int n = 1; n <= reps; ++n) {
192 int pos = rand() % (t_size -1);
193 text.replace(pos,1, hash_noise);
196 //double volume = (fabs(signal - 12.0) / 12);
197 //double old_volume = fgGetDouble("/sim/sound/voices/voice/volume");
199 //fgSetDouble("/sim/sound/voices/voice/volume", volume);
200 fgSetString("/sim/messages/atc", text.c_str());
201 //fgSetDouble("/sim/sound/voices/voice/volume", old_volume);
204 fgSetString("/sim/messages/atc", text.c_str());
211 double FGRadioTransmission::ITM_calculate_attenuation(SGGeod pos, double freq, int transmission_type) {
214 if((freq < 40.0) || (freq > 20000.0)) // frequency out of recommended range
216 /** ITM default parameters
217 TODO: take them from tile materials (especially for sea)?
219 double eps_dielect=15.0;
220 double sgm_conductivity = 0.005;
222 double frq_mhz = freq;
224 int radio_climate = 5; // continental temperate
225 int pol= _polarization;
226 double conf = 0.90; // 90% of situations and time, take into account speed
230 int p_mode = 0; // propgation mode selector: 0 LOS, 1 diffraction dominant, 2 troposcatter
234 double clutter_loss = 0.0; // loss due to vegetation and urban
235 double tx_pow = _transmitter_power;
236 double ant_gain = _rx_antenna_gain + _tx_antenna_gain;
240 double link_budget = tx_pow - _receiver_sensitivity - _rx_line_losses - _tx_line_losses + ant_gain;
241 double signal_strength = tx_pow - _rx_line_losses - _tx_line_losses + ant_gain;
242 double tx_erp = dbm_to_watt(tx_pow + _tx_antenna_gain - _tx_line_losses);
245 FGScenery * scenery = globals->get_scenery();
247 double own_lat = fgGetDouble("/position/latitude-deg");
248 double own_lon = fgGetDouble("/position/longitude-deg");
249 double own_alt_ft = fgGetDouble("/position/altitude-ft");
250 double own_heading = fgGetDouble("/orientation/heading-deg");
251 double own_alt= own_alt_ft * SG_FEET_TO_METER;
256 SGGeod own_pos = SGGeod::fromDegM( own_lon, own_lat, own_alt );
257 SGGeod max_own_pos = SGGeod::fromDegM( own_lon, own_lat, SG_MAX_ELEVATION_M );
258 SGGeoc center = SGGeoc::fromGeod( max_own_pos );
259 SGGeoc own_pos_c = SGGeoc::fromGeod( own_pos );
262 double sender_alt_ft,sender_alt;
263 double transmitter_height=0.0;
264 double receiver_height=0.0;
265 SGGeod sender_pos = pos;
267 sender_alt_ft = sender_pos.getElevationFt();
268 sender_alt = sender_alt_ft * SG_FEET_TO_METER;
269 SGGeod max_sender_pos = SGGeod::fromGeodM( pos, SG_MAX_ELEVATION_M );
270 SGGeoc sender_pos_c = SGGeoc::fromGeod( sender_pos );
273 double point_distance= _terrain_sampling_distance;
274 double course = SGGeodesy::courseRad(own_pos_c, sender_pos_c);
275 double reverse_course = SGGeodesy::courseRad(sender_pos_c, own_pos_c);
276 double distance_m = SGGeodesy::distanceM(own_pos, sender_pos);
277 double probe_distance = 0.0;
278 /** If distance larger than this value (300 km), assume reception imposssible to spare CPU cycles */
279 if (distance_m > 300000)
281 /** If above 8000 meters, consider LOS mode and calculate free-space att to spare CPU cycles */
282 if (own_alt > 8000) {
283 dbloss = 20 * log10(distance_m) +20 * log10(frq_mhz) -27.55;
284 SG_LOG(SG_GENERAL, SG_BULK,
285 "ITM Free-space mode:: Link budget: " << link_budget << ", Attenuation: " << dbloss << " dBm, free-space attenuation");
286 //cerr << "ITM Free-space mode:: Link budget: " << link_budget << ", Attenuation: " << dbloss << " dBm, free-space attenuation" << endl;
287 signal = link_budget - dbloss;
292 int max_points = (int)floor(distance_m / point_distance);
293 //double delta_last = fmod(distance_m, point_distance);
295 deque<double> elevations;
296 deque<string*> materials;
299 double elevation_under_pilot = 0.0;
300 if (scenery->get_elevation_m( max_own_pos, elevation_under_pilot, NULL )) {
301 receiver_height = own_alt - elevation_under_pilot;
304 double elevation_under_sender = 0.0;
305 if (scenery->get_elevation_m( max_sender_pos, elevation_under_sender, NULL )) {
306 transmitter_height = sender_alt - elevation_under_sender;
309 transmitter_height = sender_alt;
313 transmitter_height += _tx_antenna_height;
314 receiver_height += _rx_antenna_height;
316 //cerr << "ITM:: RX-height: " << receiver_height << " meters, TX-height: " << transmitter_height << " meters, Distance: " << distance_m << " meters" << endl;
317 _root_node->setDoubleValue("station[0]/rx-height", receiver_height);
318 _root_node->setDoubleValue("station[0]/tx-height", transmitter_height);
319 _root_node->setDoubleValue("station[0]/distance", distance_m / 1000);
321 unsigned int e_size = (deque<unsigned>::size_type)max_points;
323 while (elevations.size() <= e_size) {
324 probe_distance += point_distance;
325 SGGeod probe = SGGeod::fromGeoc(center.advanceRadM( course, probe_distance ));
326 const simgear::BVHMaterial *material = 0;
327 double elevation_m = 0.0;
329 if (scenery->get_elevation_m( probe, elevation_m, &material )) {
330 const SGMaterial *mat;
331 mat = dynamic_cast<const SGMaterial*>(material);
332 if((transmission_type == 3) || (transmission_type == 4)) {
333 elevations.push_back(elevation_m);
335 const std::vector<string> mat_names = mat->get_names();
336 string* name = new string(mat_names[0]);
337 materials.push_back(name);
340 string* no_material = new string("None");
341 materials.push_back(no_material);
345 elevations.push_front(elevation_m);
347 const std::vector<string> mat_names = mat->get_names();
348 string* name = new string(mat_names[0]);
349 materials.push_front(name);
352 string* no_material = new string("None");
353 materials.push_front(no_material);
358 if((transmission_type == 3) || (transmission_type == 4)) {
359 elevations.push_back(0.0);
360 string* no_material = new string("None");
361 materials.push_back(no_material);
364 string* no_material = new string("None");
365 elevations.push_front(0.0);
366 materials.push_front(no_material);
370 if((transmission_type == 3) || (transmission_type == 4)) {
371 elevations.push_front(elevation_under_pilot);
372 //if (delta_last > (point_distance / 2) ) // only add last point if it's farther than half point_distance
373 elevations.push_back(elevation_under_sender);
376 elevations.push_back(elevation_under_pilot);
377 //if (delta_last > (point_distance / 2) )
378 elevations.push_front(elevation_under_sender);
382 double num_points= (double)elevations.size();
385 elevations.push_front(point_distance);
386 elevations.push_front(num_points -1);
388 int size = elevations.size();
389 boost::scoped_array<double> itm_elev( new double[size] );
391 for(int i=0;i<size;i++) {
392 itm_elev[i]=elevations[i];
395 if((transmission_type == 3) || (transmission_type == 4)) {
396 // the sender and receiver roles are switched
397 ITM::point_to_point(itm_elev.get(), receiver_height, transmitter_height,
398 eps_dielect, sgm_conductivity, eno, frq_mhz, radio_climate,
399 pol, conf, rel, dbloss, strmode, p_mode, horizons, errnum);
400 if( _root_node->getBoolValue( "use-clutter-attenuation", false ) )
401 calculate_clutter_loss(frq_mhz, itm_elev.get(), materials, receiver_height, transmitter_height, p_mode, horizons, clutter_loss);
404 ITM::point_to_point(itm_elev.get(), transmitter_height, receiver_height,
405 eps_dielect, sgm_conductivity, eno, frq_mhz, radio_climate,
406 pol, conf, rel, dbloss, strmode, p_mode, horizons, errnum);
407 if( _root_node->getBoolValue( "use-clutter-attenuation", false ) )
408 calculate_clutter_loss(frq_mhz, itm_elev.get(), materials, transmitter_height, receiver_height, p_mode, horizons, clutter_loss);
411 double pol_loss = 0.0;
412 // TODO: remove this check after we check a bit the axis calculations in this function
413 if (_polarization == 1) {
414 pol_loss = polarization_loss();
416 //SG_LOG(SG_GENERAL, SG_BULK,
417 // "ITM:: Link budget: " << link_budget << ", Attenuation: " << dbloss << " dBm, " << strmode << ", Error: " << errnum);
418 //cerr << "ITM:: Link budget: " << link_budget << ", Attenuation: " << dbloss << " dBm, " << strmode << ", Error: " << errnum << endl;
419 _root_node->setDoubleValue("station[0]/link-budget", link_budget);
420 _root_node->setDoubleValue("station[0]/terrain-attenuation", dbloss);
421 _root_node->setStringValue("station[0]/prop-mode", strmode);
422 _root_node->setDoubleValue("station[0]/clutter-attenuation", clutter_loss);
423 _root_node->setDoubleValue("station[0]/polarization-attenuation", pol_loss);
424 //if (errnum == 4) // if parameters are outside sane values for lrprop, bail out fast
427 // temporary, keep this antenna radiation pattern code here
428 double tx_pattern_gain = 0.0;
429 double rx_pattern_gain = 0.0;
430 double sender_heading = 270.0; // due West
431 double tx_antenna_bearing = sender_heading - reverse_course * SGD_RADIANS_TO_DEGREES;
432 double rx_antenna_bearing = own_heading - course * SGD_RADIANS_TO_DEGREES;
433 double rx_elev_angle = atan((itm_elev[2] + transmitter_height - itm_elev[(int)itm_elev[0] + 2] + receiver_height) / distance_m) * SGD_RADIANS_TO_DEGREES;
434 double tx_elev_angle = 0.0 - rx_elev_angle;
435 if (_root_node->getBoolValue("use-tx-antenna-pattern", false)) {
436 FGRadioAntenna* TX_antenna;
437 TX_antenna = new FGRadioAntenna("Plot2");
438 TX_antenna->set_heading(sender_heading);
439 TX_antenna->set_elevation_angle(0);
440 tx_pattern_gain = TX_antenna->calculate_gain(tx_antenna_bearing, tx_elev_angle);
443 if (_root_node->getBoolValue("use-rx-antenna-pattern", false)) {
444 FGRadioAntenna* RX_antenna;
445 RX_antenna = new FGRadioAntenna("Plot2");
446 RX_antenna->set_heading(own_heading);
447 RX_antenna->set_elevation_angle(fgGetDouble("/orientation/pitch-deg"));
448 rx_pattern_gain = RX_antenna->calculate_gain(rx_antenna_bearing, rx_elev_angle);
452 signal = link_budget - dbloss - clutter_loss + pol_loss + rx_pattern_gain + tx_pattern_gain;
453 double signal_strength_dbm = signal_strength - dbloss - clutter_loss + pol_loss + rx_pattern_gain + tx_pattern_gain;
454 double field_strength_uV = dbm_to_microvolt(signal_strength_dbm);
455 _root_node->setDoubleValue("station[0]/signal-dbm", signal_strength_dbm);
456 _root_node->setDoubleValue("station[0]/field-strength-uV", field_strength_uV);
457 _root_node->setDoubleValue("station[0]/signal", signal);
458 _root_node->setDoubleValue("station[0]/tx-erp", tx_erp);
460 //_root_node->setDoubleValue("station[0]/tx-pattern-gain", tx_pattern_gain);
461 //_root_node->setDoubleValue("station[0]/rx-pattern-gain", rx_pattern_gain);
463 for (unsigned i =0; i < materials.size(); i++) {
472 void FGRadioTransmission::calculate_clutter_loss(double freq, double itm_elev[], deque<string*> &materials,
473 double transmitter_height, double receiver_height, int p_mode,
474 double horizons[], double &clutter_loss) {
476 double distance_m = itm_elev[0] * itm_elev[1]; // only consider elevation points
477 unsigned mat_size = materials.size();
478 if (p_mode == 0) { // LOS: take each point and see how clutter height affects first Fresnel zone
481 for (int k=3;k < (int)(itm_elev[0]) + 2;k++) {
483 double clutter_height = 0.0; // mean clutter height for a certain terrain type
484 double clutter_density = 0.0; // percent of reflected wave
485 if((unsigned)mat >= mat_size) { //this tends to happen when the model interferes with the antenna (obstructs)
486 //cerr << "Array index out of bounds 0-0: " << mat << " size: " << mat_size << endl;
489 get_material_properties(materials[mat], clutter_height, clutter_density);
491 double grad = fabs(itm_elev[2] + transmitter_height - itm_elev[(int)itm_elev[0] + 2] + receiver_height) / distance_m;
492 // First Fresnel radius
493 double frs_rad = 548 * sqrt( (j * itm_elev[1] * (itm_elev[0] - j) * itm_elev[1] / 1000000) / ( distance_m * freq / 1000) );
494 if (frs_rad <= 0.0) { //this tends to happen when the model interferes with the antenna (obstructs)
495 //cerr << "Frs rad 0-0: " << frs_rad << endl;
498 //double earth_h = distance_m * (distance_m - j * itm_elev[1]) / ( 1000000 * 12.75 * 1.33 ); // K=4/3
500 double min_elev = SGMiscd::min(itm_elev[2] + transmitter_height, itm_elev[(int)itm_elev[0] + 2] + receiver_height);
501 double d1 = j * itm_elev[1];
502 if ((itm_elev[2] + transmitter_height) > ( itm_elev[(int)itm_elev[0] + 2] + receiver_height) ) {
503 d1 = (itm_elev[0] - j) * itm_elev[1];
505 double ray_height = (grad * d1) + min_elev;
507 double clearance = ray_height - (itm_elev[k] + clutter_height) - frs_rad * 8/10;
508 double intrusion = fabs(clearance);
510 if (clearance >= 0) {
513 else if (clearance < 0 && (intrusion < clutter_height)) {
515 clutter_loss += clutter_density * (intrusion / (frs_rad * 2) ) * (freq/100) * (itm_elev[1]/100);
517 else if (clearance < 0 && (intrusion > clutter_height)) {
518 clutter_loss += clutter_density * (clutter_height / (frs_rad * 2 ) ) * (freq/100) * (itm_elev[1]/100);
528 else if (p_mode == 1) { // diffraction
530 if (horizons[1] == 0.0) { // single horizon: same as above, except pass twice using the highest point
531 int num_points_1st = (int)floor( horizons[0] * itm_elev[0]/ distance_m );
532 int num_points_2nd = (int)ceil( (distance_m - horizons[0]) * itm_elev[0] / distance_m );
533 //cerr << "Diffraction 1 horizon:: points1: " << num_points_1st << " points2: " << num_points_2nd << endl;
535 /** perform the first pass */
538 for (int k=3;k < num_points_1st + 2;k++) {
539 if (num_points_1st < 1)
541 double clutter_height = 0.0; // mean clutter height for a certain terrain type
542 double clutter_density = 0.0; // percent of reflected wave
544 if((unsigned)mat >= mat_size) {
545 //cerr << "Array index out of bounds 1-1: " << mat << " size: " << mat_size << endl;
548 get_material_properties(materials[mat], clutter_height, clutter_density);
550 double grad = fabs(itm_elev[2] + transmitter_height - itm_elev[num_points_1st + 2] + clutter_height) / distance_m;
551 // First Fresnel radius
552 double frs_rad = 548 * sqrt( (j * itm_elev[1] * (num_points_1st - j) * itm_elev[1] / 1000000) / ( num_points_1st * itm_elev[1] * freq / 1000) );
553 if (frs_rad <= 0.0) {
554 //cerr << "Frs rad 1-1: " << frs_rad << endl;
557 //double earth_h = distance_m * (distance_m - j * itm_elev[1]) / ( 1000000 * 12.75 * 1.33 ); // K=4/3
559 double min_elev = SGMiscd::min(itm_elev[2] + transmitter_height, itm_elev[num_points_1st + 2] + clutter_height);
560 double d1 = j * itm_elev[1];
561 if ( (itm_elev[2] + transmitter_height) > (itm_elev[num_points_1st + 2] + clutter_height) ) {
562 d1 = (num_points_1st - j) * itm_elev[1];
564 double ray_height = (grad * d1) + min_elev;
566 double clearance = ray_height - (itm_elev[k] + clutter_height) - frs_rad * 8/10;
567 double intrusion = fabs(clearance);
569 if (clearance >= 0) {
572 else if (clearance < 0 && (intrusion < clutter_height)) {
574 clutter_loss += clutter_density * (intrusion / (frs_rad * 2) ) * (freq/100) * (itm_elev[1]/100);
576 else if (clearance < 0 && (intrusion > clutter_height)) {
577 clutter_loss += clutter_density * (clutter_height / (frs_rad * 2 ) ) * (freq/100) * (itm_elev[1]/100);
587 /** and the second pass */
589 j =1; // first point is diffraction edge, 2nd the RX elevation
590 for (int k=last+2;k < (int)(itm_elev[0]) + 2;k++) {
591 if (num_points_2nd < 1)
593 double clutter_height = 0.0; // mean clutter height for a certain terrain type
594 double clutter_density = 0.0; // percent of reflected wave
596 if((unsigned)mat >= mat_size) {
597 //cerr << "Array index out of bounds 1-2: " << mat << " size: " << mat_size << endl;
600 get_material_properties(materials[mat], clutter_height, clutter_density);
602 double grad = fabs(itm_elev[last+1] + clutter_height - itm_elev[(int)itm_elev[0] + 2] + receiver_height) / distance_m;
603 // First Fresnel radius
604 double frs_rad = 548 * sqrt( (j * itm_elev[1] * (num_points_2nd - j) * itm_elev[1] / 1000000) / ( num_points_2nd * itm_elev[1] * freq / 1000) );
605 if (frs_rad <= 0.0) {
606 //cerr << "Frs rad 1-2: " << frs_rad << " numpoints2 " << num_points_2nd << " j: " << j << endl;
609 //double earth_h = distance_m * (distance_m - j * itm_elev[1]) / ( 1000000 * 12.75 * 1.33 ); // K=4/3
611 double min_elev = SGMiscd::min(itm_elev[last+1] + clutter_height, itm_elev[(int)itm_elev[0] + 2] + receiver_height);
612 double d1 = j * itm_elev[1];
613 if ( (itm_elev[last+1] + clutter_height) > (itm_elev[(int)itm_elev[0] + 2] + receiver_height) ) {
614 d1 = (num_points_2nd - j) * itm_elev[1];
616 double ray_height = (grad * d1) + min_elev;
618 double clearance = ray_height - (itm_elev[k] + clutter_height) - frs_rad * 8/10;
619 double intrusion = fabs(clearance);
621 if (clearance >= 0) {
624 else if (clearance < 0 && (intrusion < clutter_height)) {
626 clutter_loss += clutter_density * (intrusion / (frs_rad * 2) ) * (freq/100) * (itm_elev[1]/100);
628 else if (clearance < 0 && (intrusion > clutter_height)) {
629 clutter_loss += clutter_density * (clutter_height / (frs_rad * 2 ) ) * (freq/100) * (itm_elev[1]/100);
639 else { // double horizon: same as single horizon, except there are 3 segments
641 int num_points_1st = (int)floor( horizons[0] * itm_elev[0] / distance_m );
642 int num_points_2nd = (int)floor(horizons[1] * itm_elev[0] / distance_m );
643 int num_points_3rd = (int)itm_elev[0] - num_points_1st - num_points_2nd;
644 //cerr << "Double horizon:: horizon1: " << horizons[0] << " horizon2: " << horizons[1] << " distance: " << distance_m << endl;
645 //cerr << "Double horizon:: points1: " << num_points_1st << " points2: " << num_points_2nd << " points3: " << num_points_3rd << endl;
647 /** perform the first pass */
649 int j=1; // first point is TX elevation, 2nd is obstruction elevation
650 for (int k=3;k < num_points_1st +2;k++) {
651 if (num_points_1st < 1)
653 double clutter_height = 0.0; // mean clutter height for a certain terrain type
654 double clutter_density = 0.0; // percent of reflected wave
655 if((unsigned)mat >= mat_size) {
656 //cerr << "Array index out of bounds 2-1: " << mat << " size: " << mat_size << endl;
659 get_material_properties(materials[mat], clutter_height, clutter_density);
661 double grad = fabs(itm_elev[2] + transmitter_height - itm_elev[num_points_1st + 2] + clutter_height) / distance_m;
662 // First Fresnel radius
663 double frs_rad = 548 * sqrt( (j * itm_elev[1] * (num_points_1st - j) * itm_elev[1] / 1000000) / ( num_points_1st * itm_elev[1] * freq / 1000) );
664 if (frs_rad <= 0.0) {
665 //cerr << "Frs rad 2-1: " << frs_rad << " numpoints1 " << num_points_1st << " j: " << j << endl;
668 //double earth_h = distance_m * (distance_m - j * itm_elev[1]) / ( 1000000 * 12.75 * 1.33 ); // K=4/3
670 double min_elev = SGMiscd::min(itm_elev[2] + transmitter_height, itm_elev[num_points_1st + 2] + clutter_height);
671 double d1 = j * itm_elev[1];
672 if ( (itm_elev[2] + transmitter_height) > (itm_elev[num_points_1st + 2] + clutter_height) ) {
673 d1 = (num_points_1st - j) * itm_elev[1];
675 double ray_height = (grad * d1) + min_elev;
677 double clearance = ray_height - (itm_elev[k] + clutter_height) - frs_rad * 8/10;
678 double intrusion = fabs(clearance);
680 if (clearance >= 0) {
683 else if (clearance < 0 && (intrusion < clutter_height)) {
685 clutter_loss += clutter_density * (intrusion / (frs_rad * 2) ) * (freq/100) * (itm_elev[1]/100);
687 else if (clearance < 0 && (intrusion > clutter_height)) {
688 clutter_loss += clutter_density * (clutter_height / (frs_rad * 2 ) ) * (freq/100) * (itm_elev[1]/100);
698 /** and the second pass */
700 j =1; // first point is 1st obstruction elevation, 2nd is 2nd obstruction elevation
701 for (int k=last+2;k < num_points_1st + num_points_2nd +2;k++) {
702 if (num_points_2nd < 1)
704 double clutter_height = 0.0; // mean clutter height for a certain terrain type
705 double clutter_density = 0.0; // percent of reflected wave
706 if((unsigned)mat >= mat_size) {
707 //cerr << "Array index out of bounds 2-2: " << mat << " size: " << mat_size << endl;
710 get_material_properties(materials[mat], clutter_height, clutter_density);
712 double grad = fabs(itm_elev[last+1] + clutter_height - itm_elev[num_points_1st + num_points_2nd + 2] + clutter_height) / distance_m;
713 // First Fresnel radius
714 double frs_rad = 548 * sqrt( (j * itm_elev[1] * (num_points_2nd - j) * itm_elev[1] / 1000000) / ( num_points_2nd * itm_elev[1] * freq / 1000) );
715 if (frs_rad <= 0.0) {
716 //cerr << "Frs rad 2-2: " << frs_rad << " numpoints2 " << num_points_2nd << " j: " << j << endl;
719 //double earth_h = distance_m * (distance_m - j * itm_elev[1]) / ( 1000000 * 12.75 * 1.33 ); // K=4/3
721 double min_elev = SGMiscd::min(itm_elev[last+1] + clutter_height, itm_elev[num_points_1st + num_points_2nd +2] + clutter_height);
722 double d1 = j * itm_elev[1];
723 if ( (itm_elev[last+1] + clutter_height) > (itm_elev[num_points_1st + num_points_2nd + 2] + clutter_height) ) {
724 d1 = (num_points_2nd - j) * itm_elev[1];
726 double ray_height = (grad * d1) + min_elev;
728 double clearance = ray_height - (itm_elev[k] + clutter_height) - frs_rad * 8/10;
729 double intrusion = fabs(clearance);
731 if (clearance >= 0) {
734 else if (clearance < 0 && (intrusion < clutter_height)) {
736 clutter_loss += clutter_density * (intrusion / (frs_rad * 2) ) * (freq/100) * (itm_elev[1]/100);
738 else if (clearance < 0 && (intrusion > clutter_height)) {
739 clutter_loss += clutter_density * (clutter_height / (frs_rad * 2 ) ) * (freq/100) * (itm_elev[1]/100);
749 /** third and final pass */
751 j =1; // first point is 2nd obstruction elevation, 3rd is RX elevation
752 for (int k=last2+2;k < (int)itm_elev[0] + 2;k++) {
753 if (num_points_3rd < 1)
755 double clutter_height = 0.0; // mean clutter height for a certain terrain type
756 double clutter_density = 0.0; // percent of reflected wave
757 if((unsigned)mat >= mat_size) {
758 //cerr << "Array index out of bounds 2-3: " << mat << " size: " << mat_size << endl;
761 get_material_properties(materials[mat], clutter_height, clutter_density);
763 double grad = fabs(itm_elev[last2+1] + clutter_height - itm_elev[(int)itm_elev[0] + 2] + receiver_height) / distance_m;
764 // First Fresnel radius
765 double frs_rad = 548 * sqrt( (j * itm_elev[1] * (num_points_3rd - j) * itm_elev[1] / 1000000) / ( num_points_3rd * itm_elev[1] * freq / 1000) );
766 if (frs_rad <= 0.0) {
767 //cerr << "Frs rad 2-3: " << frs_rad << " numpoints3 " << num_points_3rd << " j: " << j << endl;
771 //double earth_h = distance_m * (distance_m - j * itm_elev[1]) / ( 1000000 * 12.75 * 1.33 ); // K=4/3
773 double min_elev = SGMiscd::min(itm_elev[last2+1] + clutter_height, itm_elev[(int)itm_elev[0] + 2] + receiver_height);
774 double d1 = j * itm_elev[1];
775 if ( (itm_elev[last2+1] + clutter_height) > (itm_elev[(int)itm_elev[0] + 2] + receiver_height) ) {
776 d1 = (num_points_3rd - j) * itm_elev[1];
778 double ray_height = (grad * d1) + min_elev;
780 double clearance = ray_height - (itm_elev[k] + clutter_height) - frs_rad * 8/10;
781 double intrusion = fabs(clearance);
783 if (clearance >= 0) {
786 else if (clearance < 0 && (intrusion < clutter_height)) {
788 clutter_loss += clutter_density * (intrusion / (frs_rad * 2) ) * (freq/100) * (itm_elev[1]/100);
790 else if (clearance < 0 && (intrusion > clutter_height)) {
791 clutter_loss += clutter_density * (clutter_height / (frs_rad * 2 ) ) * (freq/100) * (itm_elev[1]/100);
803 else if (p_mode == 2) { // troposcatter: ignore ground clutter for now... maybe do something with weather
810 void FGRadioTransmission::get_material_properties(string* mat_name, double &height, double &density) {
815 if(*mat_name == "Landmass") {
820 else if(*mat_name == "SomeSort") {
825 else if(*mat_name == "Island") {
829 else if(*mat_name == "Default") {
833 else if(*mat_name == "EvergreenBroadCover") {
837 else if(*mat_name == "EvergreenForest") {
841 else if(*mat_name == "DeciduousBroadCover") {
845 else if(*mat_name == "DeciduousForest") {
849 else if(*mat_name == "MixedForestCover") {
853 else if(*mat_name == "MixedForest") {
857 else if(*mat_name == "RainForest") {
861 else if(*mat_name == "EvergreenNeedleCover") {
865 else if(*mat_name == "WoodedTundraCover") {
869 else if(*mat_name == "DeciduousNeedleCover") {
873 else if(*mat_name == "ScrubCover") {
877 else if(*mat_name == "BuiltUpCover") {
881 else if(*mat_name == "Urban") {
885 else if(*mat_name == "Construction") {
889 else if(*mat_name == "Industrial") {
893 else if(*mat_name == "Port") {
897 else if(*mat_name == "Town") {
901 else if(*mat_name == "SubUrban") {
905 else if(*mat_name == "CropWoodCover") {
909 else if(*mat_name == "CropWood") {
913 else if(*mat_name == "AgroForest") {
925 double FGRadioTransmission::LOS_calculate_attenuation(SGGeod pos, double freq, int transmission_type) {
927 double frq_mhz = freq;
929 double tx_pow = _transmitter_power;
930 double ant_gain = _rx_antenna_gain + _tx_antenna_gain;
933 double sender_alt_ft,sender_alt;
934 double transmitter_height=0.0;
935 double receiver_height=0.0;
936 double own_lat = fgGetDouble("/position/latitude-deg");
937 double own_lon = fgGetDouble("/position/longitude-deg");
938 double own_alt_ft = fgGetDouble("/position/altitude-ft");
939 double own_alt= own_alt_ft * SG_FEET_TO_METER;
942 double link_budget = tx_pow - _receiver_sensitivity - _rx_line_losses - _tx_line_losses + ant_gain;
944 //cerr << "ITM:: pilot Lat: " << own_lat << ", Lon: " << own_lon << ", Alt: " << own_alt << endl;
946 SGGeod own_pos = SGGeod::fromDegM( own_lon, own_lat, own_alt );
948 SGGeod sender_pos = pos;
950 sender_alt_ft = sender_pos.getElevationFt();
951 sender_alt = sender_alt_ft * SG_FEET_TO_METER;
953 receiver_height = own_alt;
954 transmitter_height = sender_alt;
956 double distance_m = SGGeodesy::distanceM(own_pos, sender_pos);
959 transmitter_height += _tx_antenna_height;
960 receiver_height += _rx_antenna_height;
963 /** radio horizon calculation with wave bending k=4/3 */
964 double receiver_horizon = 4.12 * sqrt(receiver_height);
965 double transmitter_horizon = 4.12 * sqrt(transmitter_height);
966 double total_horizon = receiver_horizon + transmitter_horizon;
968 if (distance_m > total_horizon) {
971 double pol_loss = 0.0;
972 if (_polarization == 1) {
973 pol_loss = polarization_loss();
975 // free-space loss (distance calculation should be changed)
976 dbloss = 20 * log10(distance_m) +20 * log10(frq_mhz) -27.55;
977 signal = link_budget - dbloss + pol_loss;
979 //cerr << "LOS:: Link budget: " << link_budget << ", Attenuation: " << dbloss << " dBm " << endl;
984 /*** calculate loss due to polarization mismatch
985 * this function is only reliable for vertical polarization
986 * due to the V-shape of horizontally polarized antennas
988 double FGRadioTransmission::polarization_loss() {
991 double roll = fgGetDouble("/orientation/roll-deg");
992 if (fabs(roll) > 85.0)
994 double pitch = fgGetDouble("/orientation/pitch-deg");
995 if (fabs(pitch) > 85.0)
997 double theta = fabs( atan( sqrt(
998 pow(tan(roll * SGD_DEGREES_TO_RADIANS), 2) +
999 pow(tan(pitch * SGD_DEGREES_TO_RADIANS), 2) )) * SGD_RADIANS_TO_DEGREES);
1001 if (_polarization == 0)
1002 theta_deg = 90.0 - theta;
1005 if (theta_deg > 85.0) // we don't want to converge into infinity
1008 double loss = 10 * log10( pow(cos(theta_deg * SGD_DEGREES_TO_RADIANS), 2) );
1009 //cerr << "Polarization loss: " << loss << " dBm " << endl;
1014 double FGRadioTransmission::watt_to_dbm(double power_watt) {
1015 return 10 * log10(1000 * power_watt); // returns dbm
1018 double FGRadioTransmission::dbm_to_watt(double dbm) {
1019 return exp( (dbm-30) * log(10.0) / 10.0); // returns Watts
1022 double FGRadioTransmission::dbm_to_microvolt(double dbm) {
1023 return sqrt(dbm_to_watt(dbm) * 50) * 1000000; // returns microvolts