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Add clutter loss for single horizon diffraction

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This commit is contained in:
adrian 2011-11-27 12:53:30 +02:00
parent dd6588d4f0
commit 6b24aa0c14
1 changed files with 94 additions and 14 deletions
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108
src/Radio/radio.cxx
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@ -376,15 +376,6 @@ double FGRadio::ITM_calculate_attenuation(SGGeod pos, double freq, int transmiss
//cerr << "ITM:: itm_elev: " << _elevations[i] << endl;
}
/** first Fresnel zone radius
frequency in the middle of the bandplan, more accuracy is not necessary
*/
double fz_clr= 8.657 * sqrt(distance_m / 0.125);
// TODO: If we clear the first Fresnel zone, we are into line of sight territory
// else we need to calculate point to point link loss
if((transmission_type == 3) || (transmission_type == 4)) {
// the sender and receiver roles are switched
point_to_point(itm_elev, receiver_height, transmitter_height,
@ -422,23 +413,25 @@ void FGRadio::clutterLoss(double freq, double distance_m, double itm_elev[], deq
int j=1; // first point is TX elevation, last is RX elevation
for (int k=3;k < (int)itm_elev[0];k++) {
double clutter_height = 0.0; // clutter height hard-coded to 15 for now
double clutter_height = 0.0; // mean clutter height for a certain terrain type
double clutter_density = 0.0; // percent of reflected wave
get_material_properties(materials[j-1], clutter_height, clutter_density);
//cerr << "Clutter:: material: " << materials[j-1] << " height: " << clutter_height << ", density: " << clutter_density << endl;
double grad = fabs(itm_elev[2] + transmitter_height - itm_elev[(int)itm_elev[0] + 2] + receiver_height) / distance_m;
// First Fresnel radius
double frs_rad = 548 * sqrt( (j * itm_elev[1] * (itm_elev[0] - j) * itm_elev[1] / 1000000) / ( distance_m * freq / 1000) );
//cerr << "Clutter:: fresnel radius: " << frs_rad << endl;
//double earth_h = distance_m * (distance_m - j * itm_elev[1]) / ( 1000000 * 12.75 * 1.33 ); // K=4/3
double min_elev = SGMiscd::min(itm_elev[2] + transmitter_height, itm_elev[(int)itm_elev[0] + 2] + receiver_height);
double d1 = j * itm_elev[1];
if (fabs(min_elev - itm_elev[2]) <= 0.0001)
if ((itm_elev[2] + transmitter_height) > ( itm_elev[(int)itm_elev[0] + 2] + receiver_height) ) {
d1 = (itm_elev[0] - j) * itm_elev[1];
}
double ray_height = (grad * d1) + min_elev;
//cerr << "Clutter:: ray height: " << ray_height << " ground height:" << itm_elev[k] << endl;
double clearance = ray_height - (itm_elev[k] + clutter_height) - frs_rad;
cerr << "Clutter:: ray height: " << ray_height << " ground height:" << itm_elev[k] << endl;
double clearance = ray_height - (itm_elev[k] + clutter_height) - frs_rad * 8/10;
double intrusion = fabs(clearance);
//cerr << "Clutter:: clearance: " << clearance << endl;
if (clearance >= 0) {
@ -449,7 +442,7 @@ void FGRadio::clutterLoss(double freq, double distance_m, double itm_elev[], deq
clutter_loss += clutter_density * (intrusion / (frs_rad * 2) ) * freq/100;
}
else if (clearance < 0 && (intrusion > clutter_height)) {
clutter_loss += clutter_density * (clutter_height / (frs_rad *2 ) ) * freq/100;
clutter_loss += clutter_density * (clutter_height / (frs_rad * 2 ) ) * freq/100;
}
else {
clutter_loss += 0.0;
@ -461,6 +454,93 @@ void FGRadio::clutterLoss(double freq, double distance_m, double itm_elev[], deq
else if (p_mode == 1) { // diffraction
if (horizons[1] == 0.0) { // single horizon: same as above, except pass twice using the highest point
int num_points_1st = (int)floor( horizons[1] * (double)itm_elev[0] / distance_m );
int num_points_2nd = (int)floor( (distance_m - horizons[1]) * (double)itm_elev[0] / distance_m );
int last = 1;
/** perform the first pass */
int j=1; // first point is TX elevation, last is obstruction elevation
for (int k=3;k < num_points_1st ;k++) {
double clutter_height = 0.0; // mean clutter height for a certain terrain type
double clutter_density = 0.0; // percent of reflected wave
get_material_properties(materials[j-1], clutter_height, clutter_density);
//cerr << "Clutter:: material: " << materials[j-1] << " height: " << clutter_height << ", density: " << clutter_density << endl;
double grad = fabs(itm_elev[2] + transmitter_height - itm_elev[num_points_1st + 2] + clutter_height) / distance_m;
// First Fresnel radius
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) );
//cerr << "Clutter:: fresnel radius: " << frs_rad << endl;
//double earth_h = distance_m * (distance_m - j * itm_elev[1]) / ( 1000000 * 12.75 * 1.33 ); // K=4/3
double min_elev = SGMiscd::min(itm_elev[2] + transmitter_height, itm_elev[num_points_1st + 2] + clutter_height);
double d1 = j * itm_elev[1];
if ( (itm_elev[2] + transmitter_height) > (itm_elev[num_points_1st + 2] + clutter_height) ) {
d1 = (num_points_1st - j) * itm_elev[1];
}
double ray_height = (grad * d1) + min_elev;
//cerr << "Clutter:: ray height: " << ray_height << " ground height:" << itm_elev[k] << endl;
double clearance = ray_height - (itm_elev[k] + clutter_height) - frs_rad * 8/10;
double intrusion = fabs(clearance);
//cerr << "Clutter:: clearance: " << clearance << endl;
if (clearance >= 0) {
clutter_loss +=0.0;
}
else if (clearance < 0 && (intrusion < clutter_height)) {
clutter_loss += clutter_density * (intrusion / (frs_rad * 2) ) * freq/100;
}
else if (clearance < 0 && (intrusion > clutter_height)) {
clutter_loss += clutter_density * (clutter_height / (frs_rad * 2 ) ) * freq/100;
}
else {
clutter_loss += 0.0;
}
j++;
last = k+1;
}
/** and the second pass */
int l =1;
for (int k=last;k < num_points_2nd ;k++) {
double clutter_height = 0.0; // mean clutter height for a certain terrain type
double clutter_density = 0.0; // percent of reflected wave
get_material_properties(materials[j-1], clutter_height, clutter_density);
//cerr << "Clutter:: material: " << materials[j-1] << " height: " << clutter_height << ", density: " << clutter_density << endl;
double grad = fabs(itm_elev[last] + clutter_height - itm_elev[(int)itm_elev[0] + 2] + receiver_height) / distance_m;
// First Fresnel radius
double frs_rad = 548 * sqrt( (l * itm_elev[1] * (num_points_2nd - l) * itm_elev[1] / 1000000) / ( num_points_2nd * itm_elev[1] * freq / 1000) );
//cerr << "Clutter:: fresnel radius: " << frs_rad << endl;
//double earth_h = distance_m * (distance_m - j * itm_elev[1]) / ( 1000000 * 12.75 * 1.33 ); // K=4/3
double min_elev = SGMiscd::min(itm_elev[last] + clutter_height, itm_elev[(int)itm_elev[0] + 2] + receiver_height);
double d1 = l * itm_elev[1];
if ( (itm_elev[last] + clutter_height) > (itm_elev[(int)itm_elev[0] + 2] + receiver_height) ) {
d1 = (num_points_2nd - l) * itm_elev[1];
}
double ray_height = (grad * d1) + min_elev;
//cerr << "Clutter:: ray height: " << ray_height << " ground height:" << itm_elev[k] << endl;
double clearance = ray_height - (itm_elev[k] + clutter_height) - frs_rad * 8/10;
double intrusion = fabs(clearance);
//cerr << "Clutter:: clearance: " << clearance << endl;
if (clearance >= 0) {
clutter_loss +=0.0;
}
else if (clearance < 0 && (intrusion < clutter_height)) {
clutter_loss += clutter_density * (intrusion / (frs_rad * 2) ) * freq/100;
}
else if (clearance < 0 && (intrusion > clutter_height)) {
clutter_loss += clutter_density * (clutter_height / (frs_rad * 2 ) ) * freq/100;
}
else {
clutter_loss += 0.0;
}
j++;
}
}
else { // double horizon: same as single horizon, except there are 3 segments