1 // antenna.cxx -- implementation of FGRadioAntenna
2 // Class to represent a virtual radio antenna properties
3 // Written by Adrian Musceac YO8RZZ, started December 2011.
4 //
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.
9 //
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.
14 //
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.
18
19
20 #ifdef HAVE_CONFIG_H
21 # include <config.h>
22 #endif
23
24 #include <cmath>
25 #include <iostream>
26 #include <stdlib.h>
27 #include <fstream>
28 #include <Scenery/scenery.hxx>
29 #include <simgear/io/iostreams/sgstream.hxx>
30
31 #include "antenna.hxx"
32
33 using namespace std;
34
FGRadioAntenna(string type)35 FGRadioAntenna::FGRadioAntenna(string type) {
36
37 _mirror_y = 1; // normally we want to mirror these axis because the pattern is simetric
38 _mirror_z = 1;
39 _invert_ground = 0; // TODO: use for inverting the antenna ground, for instance aircraft body reflection
40 load_NEC_antenna_pattern(type);
41 }
42
~FGRadioAntenna()43 FGRadioAntenna::~FGRadioAntenna() {
44 for (unsigned i =0; i < _pattern.size(); i++) {
45 AntennaGain *point_gain = _pattern[i];
46 delete point_gain;
47 }
48 _pattern.clear();
49 }
50
51 // WIP
calculate_gain(double bearing,double angle)52 double FGRadioAntenna::calculate_gain(double bearing, double angle) {
53
54 // TODO: what if the pattern is assimetric?
55 bearing = fabs(bearing);
56 if (bearing > 180)
57 bearing = 360 - bearing;
58 // for plots with 2 degrees resolution:
59 int azimuth = (int)floor(bearing);
60 azimuth += azimuth % 2;
61 int elevation = (int)floor(angle);
62 elevation += elevation % 2;
63 //cerr << "Bearing: " << bearing << " angle: " << angle << " azimuth: " << azimuth << " elevation: " << elevation << endl;
64 for (unsigned i =0; i < _pattern.size(); i++) {
65 AntennaGain *point_gain = _pattern[i];
66
67 if ( (azimuth == point_gain->azimuth) && (elevation == point_gain->elevation)) {
68 return point_gain->gain;
69 }
70 }
71
72 return 0;
73 }
74
75
load_NEC_antenna_pattern(string type)76 void FGRadioAntenna::load_NEC_antenna_pattern(string type) {
77
78 //SGPath pattern_file(globals->get_fg_home());
79 SGPath pattern_file(globals->get_fg_root());
80 pattern_file.append("Navaids/Antennas");
81 pattern_file.append(type + ".txt");
82 if (!pattern_file.exists()) {
83 return;
84 }
85 sg_ifstream file_in(pattern_file);
86 int heading, elevation;
87 double gain;
88 while(!file_in.eof()) {
89 file_in >> heading >> elevation >> gain;
90 if( (_mirror_y == 1) && (heading > 180) ) {
91 continue;
92 }
93 if ( (_mirror_z == 1) && (elevation < 0) ) {
94 continue;
95 }
96 //cerr << "head: " << heading << " elev: " << elevation << " gain: " << gain << endl;
97 AntennaGain *datapoint = new AntennaGain;
98 datapoint->azimuth = heading;
99 datapoint->elevation = 90.0 - abs(elevation);
100 datapoint->gain = gain;
101 _pattern.push_back(datapoint);
102 }
103 }
104