Use landcover to determine ground clutter path loss for LOS
modified: src/Radio/itm.cpp modified: src/Radio/radio.cxx modified: src/Radio/radio.hxx
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adrian
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b2e83c4dcc
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dd6588d4f0
3 changed files with 248 additions and 15 deletions
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@ -1519,6 +1519,8 @@ void point_to_point(double elev[],
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double rel, // 0.01 .. .99, Fractions of time
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double &dbloss,
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char *strmode,
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int &p_mode, // propagation mode selector
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double (&horizons)[2], // horizon distances
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int &errnum)
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{
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// radio_climate: 1-Equatorial, 2-Continental Subtropical, 3-Maritime Tropical,
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@ -1568,22 +1570,38 @@ void point_to_point(double elev[],
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fs = 32.45 + 20.0 * log10(frq_mhz) + 20.0 * log10(prop.d / 1000.0);
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q = prop.d - prop.d_L;
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horizons[0] = 0.0;
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horizons[1] = 0.0;
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if (int(q) < 0.0) {
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strcpy(strmode, "Line-Of-Sight Mode");
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p_mode = 0;
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} else {
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if (int(q) == 0.0)
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if (int(q) == 0.0) {
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strcpy(strmode, "Single Horizon");
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horizons[0] = prop.d_Lj[0];
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p_mode = 1;
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}
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else
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if (int(q) > 0.0)
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else {
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if (int(q) > 0.0) {
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strcpy(strmode, "Double Horizon");
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horizons[0] = prop.d_Lj[0];
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horizons[1] = prop.d_Lj[1];
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p_mode = 1;
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}
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}
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if (prop.d <= prop.d_Ls || prop.d <= prop.dx)
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if (prop.d <= prop.d_Ls || prop.d <= prop.dx) {
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strcat(strmode, ", Diffraction Dominant");
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p_mode = 1;
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}
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else
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if (prop.d > prop.dx)
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strcat(strmode, ", Troposcatter Dominant");
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else {
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if (prop.d > prop.dx) {
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strcat(strmode, ", Troposcatter Dominant");
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p_mode = 2;
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}
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}
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}
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dbloss = avar(zr, 0.0, zc, prop, propv) + fs;
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@ -26,6 +26,7 @@
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#include <stdlib.h>
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#include <deque>
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#include "radio.hxx"
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#include <simgear/scene/material/mat.hxx>
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#include <Scenery/scenery.hxx>
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#define WITH_POINT_TO_POINT 1
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@ -213,8 +214,11 @@ double FGRadio::ITM_calculate_attenuation(SGGeod pos, double freq, int transmiss
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double rel = 0.90;
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double dbloss;
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char strmode[150];
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int p_mode = 0; // propgation mode selector: 0 LOS, 1 diffraction dominant, 2 troposcatter
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double horizons[2];
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int errnum;
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double clutter_loss; // loss due to vegetation and urban
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double tx_pow = _transmitter_power;
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double ant_gain = _antenna_gain;
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double signal = 0.0;
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@ -278,6 +282,8 @@ double FGRadio::ITM_calculate_attenuation(SGGeod pos, double freq, int transmiss
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double max_points = distance_m / point_distance;
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deque<double> _elevations;
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deque<string> materials;
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double elevation_under_pilot = 0.0;
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if (scenery->get_elevation_m( max_own_pos, elevation_under_pilot, NULL )) {
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@ -306,23 +312,39 @@ double FGRadio::ITM_calculate_attenuation(SGGeod pos, double freq, int transmiss
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while (_elevations.size() <= e_size) {
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probe_distance += point_distance;
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SGGeod probe = SGGeod::fromGeoc(center.advanceRadM( course, probe_distance ));
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const SGMaterial *mat = 0;
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double elevation_m = 0.0;
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if (scenery->get_elevation_m( probe, elevation_m, NULL )) {
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if (scenery->get_elevation_m( probe, elevation_m, &mat )) {
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if((transmission_type == 3) || (transmission_type == 4)) {
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_elevations.push_back(elevation_m);
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if(mat) {
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const std::vector<string> mat_names = mat->get_names();
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materials.push_back(mat_names[0]);
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}
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else {
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materials.push_back("None");
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}
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}
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else {
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_elevations.push_front(elevation_m);
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if(mat) {
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const std::vector<string> mat_names = mat->get_names();
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materials.push_front(mat_names[0]);
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}
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else {
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materials.push_front("None");
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}
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}
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}
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else {
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if((transmission_type == 3) || (transmission_type == 4)) {
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_elevations.push_back(elevation_m);
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_elevations.push_back(0.0);
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materials.push_back("None");
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}
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else {
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_elevations.push_front(0.0);
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_elevations.push_front(0.0);
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materials.push_front("None");
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}
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}
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}
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@ -367,25 +389,205 @@ double FGRadio::ITM_calculate_attenuation(SGGeod pos, double freq, int transmiss
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// the sender and receiver roles are switched
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point_to_point(itm_elev, receiver_height, transmitter_height,
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eps_dielect, sgm_conductivity, eno, frq_mhz, radio_climate,
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pol, conf, rel, dbloss, strmode, errnum);
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pol, conf, rel, dbloss, strmode, p_mode, horizons, errnum);
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}
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else {
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point_to_point(itm_elev, transmitter_height, receiver_height,
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eps_dielect, sgm_conductivity, eno, frq_mhz, radio_climate,
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pol, conf, rel, dbloss, strmode, errnum);
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pol, conf, rel, dbloss, strmode, p_mode, horizons, errnum);
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}
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SG_LOG(SG_GENERAL, SG_BULK,
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"ITM:: Link budget: " << link_budget << ", Attenuation: " << dbloss << " dBm, " << strmode << ", Error: " << errnum);
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cerr << "ITM:: Link budget: " << link_budget << ", Attenuation: " << dbloss << " dBm, " << strmode << ", Error: " << errnum << endl;
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clutterLoss(frq_mhz, distance_m, itm_elev, materials, transmitter_height, receiver_height, p_mode, horizons, clutter_loss);
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cerr << "Clutter loss: " << clutter_loss << endl;
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//if (errnum == 4) // if parameters are outside sane values for lrprop, the alternative method is used
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// return -1;
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signal = link_budget - dbloss;
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signal = link_budget - dbloss - clutter_loss;
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return signal;
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}
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/*** Calculate losses due to vegetation and urban clutter (WIP)
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* We are only worried about clutter loss, terrain influence
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* on the first Fresnel zone is calculated in the ITM functions
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***/
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void FGRadio::clutterLoss(double freq, double distance_m, double itm_elev[], deque<string> materials,
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double transmitter_height, double receiver_height, int p_mode,
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double horizons[], double &clutter_loss) {
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if (p_mode == 0) { // LOS: take each point and see how clutter height affects first Fresnel zone
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int j=1; // first point is TX elevation, last is RX elevation
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for (int k=3;k < (int)itm_elev[0];k++) {
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double clutter_height = 0.0; // clutter height hard-coded to 15 for now
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double clutter_density = 0.0; // percent of reflected wave
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get_material_properties(materials[j-1], clutter_height, clutter_density);
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//cerr << "Clutter:: material: " << materials[j-1] << " height: " << clutter_height << ", density: " << clutter_density << endl;
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double grad = fabs(itm_elev[2] + transmitter_height - itm_elev[(int)itm_elev[0] + 2] + receiver_height) / distance_m;
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// First Fresnel radius
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double frs_rad = 548 * sqrt( (j * itm_elev[1] * (itm_elev[0] - j) * itm_elev[1] / 1000000) / ( distance_m * freq / 1000) );
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//cerr << "Clutter:: fresnel radius: " << frs_rad << endl;
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//double earth_h = distance_m * (distance_m - j * itm_elev[1]) / ( 1000000 * 12.75 * 1.33 ); // K=4/3
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double min_elev = SGMiscd::min(itm_elev[2] + transmitter_height, itm_elev[(int)itm_elev[0] + 2] + receiver_height);
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double d1 = j * itm_elev[1];
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if (fabs(min_elev - itm_elev[2]) <= 0.0001)
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d1 = (itm_elev[0] - j) * itm_elev[1];
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double ray_height = (grad * d1) + min_elev;
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//cerr << "Clutter:: ray height: " << ray_height << " ground height:" << itm_elev[k] << endl;
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double clearance = ray_height - (itm_elev[k] + clutter_height) - frs_rad;
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double intrusion = fabs(clearance);
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//cerr << "Clutter:: clearance: " << clearance << endl;
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if (clearance >= 0) {
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clutter_loss +=0.0;
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}
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else if (clearance < 0 && (intrusion < clutter_height)) {
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clutter_loss += clutter_density * (intrusion / (frs_rad * 2) ) * freq/100;
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}
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else if (clearance < 0 && (intrusion > clutter_height)) {
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clutter_loss += clutter_density * (clutter_height / (frs_rad *2 ) ) * freq/100;
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}
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else {
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clutter_loss += 0.0;
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}
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j++;
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}
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}
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else if (p_mode == 1) { // diffraction
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if (horizons[1] == 0.0) { // single horizon: same as above, except pass twice using the highest point
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}
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else { // double horizon: same as single horizon, except there are 3 segments
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}
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}
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else if (p_mode == 2) { // troposcatter: use the first smooth earth horizon as mid point
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}
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}
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/*** Material properties database
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* height: median clutter height
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* density: radiowave attenuation factor
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***/
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void FGRadio::get_material_properties(string mat_name, double &height, double &density) {
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if(mat_name == "Landmass") {
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height = 15.0;
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density = 0.2;
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}
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else if(mat_name == "SomeSort") {
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height = 15.0;
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density = 0.2;
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}
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else if(mat_name == "Island") {
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height = 15.0;
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density = 0.2;
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}
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else if(mat_name == "Default") {
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height = 15.0;
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density = 0.2;
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}
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else if(mat_name == "EvergreenBroadCover") {
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height = 20.0;
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density = 0.2;
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}
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else if(mat_name == "EvergreenForest") {
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height = 20.0;
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density = 0.2;
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}
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else if(mat_name == "DeciduousBroadCover") {
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height = 15.0;
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density = 0.3;
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}
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else if(mat_name == "DeciduousForest") {
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height = 15.0;
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density = 0.3;
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}
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else if(mat_name == "MixedForestCover") {
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height = 20.0;
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density = 0.25;
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}
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else if(mat_name == "MixedForest") {
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height = 15.0;
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density = 0.25;
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}
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else if(mat_name == "RainForest") {
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height = 25.0;
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density = 0.55;
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}
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else if(mat_name == "EvergreenNeedleCover") {
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height = 15.0;
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density = 0.2;
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}
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else if(mat_name == "WoodedTundraCover") {
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height = 5.0;
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density = 0.15;
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}
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else if(mat_name == "DeciduousNeedleCover") {
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height = 5.0;
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density = 0.2;
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}
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else if(mat_name == "ScrubCover") {
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height = 3.0;
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density = 0.15;
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}
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else if(mat_name == "BuiltUpCover") {
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height = 30.0;
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density = 0.7;
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}
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else if(mat_name == "Urban") {
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height = 30.0;
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density = 0.7;
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}
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else if(mat_name == "Construction") {
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height = 30.0;
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density = 0.7;
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}
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else if(mat_name == "Industrial") {
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height = 30.0;
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density = 0.7;
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}
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else if(mat_name == "Port") {
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height = 30.0;
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density = 0.7;
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}
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else if(mat_name == "Town") {
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height = 10.0;
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density = 0.5;
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}
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else if(mat_name == "SubUrban") {
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height = 10.0;
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density = 0.5;
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}
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else if(mat_name == "CropWoodCover") {
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height = 10.0;
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density = 0.1;
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}
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else if(mat_name == "CropWood") {
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height = 10.0;
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density = 0.1;
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}
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else if(mat_name == "AgroForest") {
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height = 10.0;
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density = 0.1;
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}
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else {
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height = 0.0;
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density = 0.0;
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}
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}
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/*** implement simple LOS propagation model (WIP)
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***/
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double FGRadio::LOS_calculate_attenuation(SGGeod pos, double freq, int transmission_type) {
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@ -453,3 +655,10 @@ double FGRadio::LOS_calculate_attenuation(SGGeod pos, double freq, int transmiss
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return signal;
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}
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/*** Material properties database
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***/
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void FGRadio::set_material_properties() {
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}
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@ -23,7 +23,7 @@
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#include <simgear/compiler.h>
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#include <simgear/structure/subsystem_mgr.hxx>
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#include <deque>
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#include <Main/fg_props.hxx>
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#include <simgear/math/sg_geodesy.hxx>
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@ -43,10 +43,16 @@ private:
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double _receiver_sensitivity;
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double _transmitter_power;
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double _antenna_gain;
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std::map<string, double[2]> _mat_database;
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int _propagation_model; /// 0 none, 1 round Earth, 2 ITM
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double ITM_calculate_attenuation(SGGeod tx_pos, double freq, int ground_to_air);
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double LOS_calculate_attenuation(SGGeod tx_pos, double freq, int ground_to_air);
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void clutterLoss(double freq, double distance_m, double itm_elev[], std::deque<string> materials,
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double transmitter_height, double receiver_height, int p_mode,
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double horizons[], double &clutter_loss);
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void set_material_properties();
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void get_material_properties(string mat_name, double &height, double &density);
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public:
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