1 // dme.cxx -- class to manage an instance of the DME
3 // Written by Curtis Olson, started April 2000.
5 // Copyright (C) 2000 Curtis L. Olson - curt@flightgear.org
7 // This program is free software; you can redistribute it and/or
8 // modify it under the terms of the GNU General Public License as
9 // published by the Free Software Foundation; either version 2 of the
10 // License, or (at your option) any later version.
12 // This program is distributed in the hope that it will be useful, but
13 // WITHOUT ANY WARRANTY; without even the implied warranty of
14 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 // General Public License for more details.
17 // You should have received a copy of the GNU General Public License
18 // along with this program; if not, write to the Free Software
19 // Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
28 #include <stdio.h> // snprintf
30 #include <simgear/compiler.h>
31 #include <simgear/math/sg_random.h>
33 #include <Aircraft/aircraft.hxx>
34 #include <Navaids/ilslist.hxx>
35 #include <Navaids/mkrbeacons.hxx>
36 #include <Navaids/navlist.hxx>
45 * Boy, this is ugly! Make the VOR range vary by altitude difference.
47 static double kludgeRange ( double stationElev, double aircraftElev,
50 // Assume that the nominal range (usually
51 // 50nm) applies at a 5,000 ft difference.
53 double factor = (aircraftElev - stationElev)*SG_METER_TO_FEET / 5000.0;
54 double range = fabs(nominalRange * factor);
56 // Clamp the range to keep it sane; for
57 // now, never less than 25% or more than
58 // 500% of nominal range.
59 if (range < nominalRange/4.0) {
60 range = nominalRange/4.0;
61 } else if (range > nominalRange*5.0) {
62 range = nominalRange*5.0;
71 lon_node(fgGetNode("/position/longitude-deg", true)),
72 lat_node(fgGetNode("/position/latitude-deg", true)),
73 alt_node(fgGetNode("/position/altitude-ft", true)),
74 bus_power(fgGetNode("/systems/electrical/outputs/dme", true)),
75 navcom1_bus_power(fgGetNode("/systems/electrical/outputs/navcom[0]", true)),
76 navcom2_bus_power(fgGetNode("/systems/electrical/outputs/navcom[1]", true)),
77 navcom1_power_btn(fgGetNode("/radios/comm[0]/inputs/power-btn", true)),
78 navcom2_power_btn(fgGetNode("/radios/comm[1]/inputs/power-btn", true)),
79 navcom1_freq(fgGetNode("/radios/nav[0]/frequencies/selected-mhz", true)),
80 navcom2_freq(fgGetNode("/radios/nav[1]/frequencies/selected-mhz", true)),
108 fgTie("/radios/dme/frequencies/selected-khz", this,
109 &FGDME::get_freq, &FGDME::set_freq);
112 fgTie("/radios/dme/in-range", this, &FGDME::get_inrange);
114 fgTie("/radios/dme/distance-nm", this, &FGDME::get_dist);
116 fgTie("/radios/dme/speed-kt", this, &FGDME::get_spd);
118 fgTie("/radios/dme/ete-min", this, &FGDME::get_ete);
124 fgUntie("/radios/dme/frequencies/selected-khz");
127 fgUntie("/radios/dme/in-range");
128 fgUntie("/radios/dme/distance-nm");
129 fgUntie("/radios/dme/speed-kt");
130 fgUntie("/radios/dme/ete-min");
134 // Update the various nav values based on position and valid tuned in navs
136 FGDME::update(double dt)
138 double lon = lon_node->getDoubleValue() * SGD_DEGREES_TO_RADIANS;
139 double lat = lat_node->getDoubleValue() * SGD_DEGREES_TO_RADIANS;
140 double elev = alt_node->getDoubleValue() * SG_FEET_TO_METER;
144 Point3D aircraft = sgGeodToCart( Point3D( lon, lat, elev ) );
147 if ( valid && has_power() ) {
148 station = Point3D( x, y, z );
149 dist = aircraft.distance3D( station ) * SG_METER_TO_NM;
150 effective_range = kludgeRange(elev, elev, range);
151 if (dist < effective_range * SG_NM_TO_METER) {
153 } else if (dist < 2 * effective_range * SG_NM_TO_METER) {
154 inrange = sg_random() <
155 (2 * effective_range * SG_NM_TO_METER - dist) /
156 (effective_range * SG_NM_TO_METER);
161 SGTimeStamp current_time;
162 station = Point3D( x, y, z );
163 dist = aircraft.distance3D( station ) * SG_METER_TO_NM;
164 current_time.stamp();
165 long dMs = (current_time - last_time) / 1000;
166 // Update every second
168 double dDist = dist - prev_dist;
169 spd = fabs((dDist/dMs) * 3600000);
170 // FIXME: the panel should be able to
174 ete = fabs((dist/spd) * 60.0);
175 // FIXME: the panel should be able to
193 // Update current nav/adf radio stations based on current postition
196 double lon = lon_node->getDoubleValue() * SGD_DEGREES_TO_RADIANS;
197 double lat = lat_node->getDoubleValue() * SGD_DEGREES_TO_RADIANS;
198 double elev = alt_node->getDoubleValue() * SG_FEET_TO_METER;
200 // FIXME: the panel should handle this
201 // don't worry about overhead for now,
202 // since this is handled only periodically
203 switch_pos = fgGetInt("/radios/dme/switch-position", 2);
204 if ( switch_pos == 1 && has_power() && navcom1_on() ) {
205 if ( freq != navcom1_freq->getDoubleValue() ) {
206 freq = navcom1_freq->getDoubleValue();
209 } else if ( switch_pos == 3 && has_power() && navcom2_on() ) {
210 if ( freq != navcom2_freq->getDoubleValue() ) {
211 freq = navcom2_freq->getDoubleValue();
214 } else if ( switch_pos == 2 && has_power() ) {
224 if ( (ils = current_ilslist->findByFreq( freq, lon, lat, elev )) != NULL ) {
225 if ( ils->get_has_dme() ) {
227 lon = ils->get_loclon();
228 lat = ils->get_loclat();
229 elev = ils->get_gselev();
230 range = FG_ILS_DEFAULT_RANGE;
231 effective_range = kludgeRange(elev, elev, range);
232 x = ils->get_dme_x();
233 y = ils->get_dme_y();
234 z = ils->get_dme_z();
236 } else if ( (nav = current_navlist->findByFreq(freq, lon, lat, elev)) != NULL ) {
237 if (nav->get_has_dme()) {
239 lon = nav->get_lon();
240 lat = nav->get_lat();
241 elev = nav->get_elev_ft();
242 range = nav->get_range();
243 effective_range = kludgeRange(elev, elev, range);