From: adrian Date: Sun, 27 Nov 2011 10:53:30 +0000 (+0200) Subject: Add clutter loss for single horizon diffraction X-Git-Url: https://git.mxchange.org/?a=commitdiff_plain;h=6b24aa0c14f92d268faead3cfe1dc3fd601898dd;p=flightgear.git Add clutter loss for single horizon diffraction --- diff --git a/src/Radio/radio.cxx b/src/Radio/radio.cxx index 72fdb15d8..314e40c63 100644 --- a/src/Radio/radio.cxx +++ b/src/Radio/radio.cxx @@ -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