New version of basic DME support. This can coexist with the old one
for a little while, since it uses different properties. There are some improvements, especially with searching and range. It also has its own serviceable and in-range properties, independent of any coupled VOR.
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david
parent
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4 changed files with 266 additions and 0 deletions
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@ -1,6 +1,7 @@
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noinst_LIBRARIES = libInstrumentation.a
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libInstrumentation_a_SOURCES = instrument_mgr.cxx instrument_mgr.hxx \
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dme.cxx dme.hxx \
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gyro.cxx gyro.hxx \
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airspeed_indicator.cxx airspeed_indicator.hxx \
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attitude_indicator.cxx attitude_indicator.hxx \
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183
src/Instrumentation/dme.cxx
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183
src/Instrumentation/dme.cxx
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// dme.cxx - distance-measuring equipment.
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// Written by David Megginson, started 2003.
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//
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// This file is in the Public Domain and comes with no warranty.
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#include <simgear/compiler.h>
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#include <simgear/math/sg_geodesy.hxx>
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#include <simgear/math/sg_random.h>
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#include <Main/fg_props.hxx>
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#include <Navaids/ilslist.hxx>
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#include <Navaids/navlist.hxx>
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#include "dme.hxx"
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/**
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* Adjust the range.
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*
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* Start by calculating the radar horizon based on the elevation
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* difference, then clamp to the maximum, then add a fudge for
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* borderline reception.
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*/
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static double
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adjust_range (double transmitter_elevation_ft, double aircraft_altitude_ft,
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double max_range_nm)
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{
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double delta_elevation_ft =
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fabs(aircraft_altitude_ft - transmitter_elevation_ft);
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double range_nm = 1.23 * sqrt(delta_elevation_ft);
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if (range_nm > max_range_nm)
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range_nm = max_range_nm;
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double rand = sg_random();
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return range_nm + (range_nm * rand * rand);
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}
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DME::DME ()
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: _last_distance_nm(0),
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_last_frequency_mhz(-1),
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_time_before_search_sec(0),
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_transmitter_valid(false),
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_transmitter_elevation_ft(0),
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_transmitter_range_nm(0)
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{
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}
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DME::~DME ()
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{
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}
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void
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DME::init ()
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{
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_longitude_node = fgGetNode("/position/longitude-deg", true);
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_latitude_node = fgGetNode("/position/latitude-deg", true);
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_altitude_node = fgGetNode("/position/altitude-deg", true);
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_serviceable_node = fgGetNode("/instrumentation/dme/serviceable", true);
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_electrical_node = fgGetNode("/systems/electrical/outputs/dme", true);
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_source_node = fgGetNode("/instrumentation/dme/frequencies/source", true);
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_frequency_node =
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fgGetNode("/instrumentation/dme/frequencies/selected-mhz", true);
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_in_range_node = fgGetNode("/instrumentation/dme/in-range", true);
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_distance_node =
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fgGetNode("/instrumentation/dme/indicated-distance-nm", true);
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_speed_node =
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fgGetNode("/instrumentation/dme/indicated-ground-speed-kt", true);
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_time_node =
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fgGetNode("/instrumentation/dme/indicated-time-min", true);
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}
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void
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DME::update (double delta_time_sec)
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{
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// Figure out the source
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const char * source = _source_node->getStringValue();
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if (source[0] == '\0') {
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source = "/instrumentation/dme/frequencies/selected-mhz";
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_source_node->setStringValue(source);
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}
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// Get the frequency
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double frequency_mhz = fgGetDouble(source, 108.0);
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if (frequency_mhz != _last_frequency_mhz) {
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_time_before_search_sec = 0;
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_last_frequency_mhz = frequency_mhz;
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}
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// Get the aircraft position
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double longitude_rad =
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_longitude_node->getDoubleValue() * SGD_DEGREES_TO_RADIANS;
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double latitude_rad =
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_latitude_node->getDoubleValue() * SGD_DEGREES_TO_RADIANS;
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double altitude_m =
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_altitude_node->getDoubleValue() * SGD_DEGREES_TO_RADIANS;
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// On timeout, scan again
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_time_before_search_sec -= delta_time_sec;
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if (_time_before_search_sec < 0)
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search(frequency_mhz, longitude_rad,
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latitude_rad, altitude_m);
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// If it's off, don't bother.
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if (!_serviceable_node->getBoolValue() ||
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!_electrical_node->getBoolValue() ||
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!_transmitter_valid) {
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_last_distance_nm = 0;
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_in_range_node->setBoolValue(false);
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_distance_node->setDoubleValue(0);
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_speed_node->setDoubleValue(0);
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_time_node->setDoubleValue(0);
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return;
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}
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// Calculate the distance to the transmitter
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Point3D location =
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sgGeodToCart(Point3D(longitude_rad, latitude_rad, altitude_m));
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double distance_nm = _transmitter.distance3D(location) * SG_METER_TO_NM;
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double range_nm = adjust_range(_transmitter_elevation_ft,
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altitude_m * SG_METER_TO_FEET,
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_transmitter_range_nm);
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if (distance_nm <= range_nm) {
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double speed_kt = (fabs(distance_nm - _last_distance_nm) *
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((1 / delta_time_sec) * 3600.0));
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_last_distance_nm = distance_nm;
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_in_range_node->setBoolValue(true);
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_distance_node->setDoubleValue(distance_nm);
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_speed_node->setDoubleValue(speed_kt);
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_time_node->setDoubleValue(distance_nm/speed_kt*60.0);
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} else {
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_last_distance_nm = 0;
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_in_range_node->setBoolValue(false);
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_distance_node->setDoubleValue(0);
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_speed_node->setDoubleValue(0);
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_time_node->setDoubleValue(0);
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}
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}
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void
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DME::search (double frequency_mhz, double longitude_rad,
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double latitude_rad, double altitude_m)
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{
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// reset search time
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_time_before_search_sec = 1.0;
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// try the ILS list first
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FGILS * ils = current_ilslist->findByFreq(frequency_mhz,
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longitude_rad,
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latitude_rad,
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altitude_m);
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if (ils != 0 && ils->get_has_dme()) {
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_transmitter_valid = true;
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_transmitter = Point3D(ils->get_dme_x(),
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ils->get_dme_y(),
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ils->get_dme_z());
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_transmitter_elevation_ft = ils->get_gselev() * SG_METER_TO_FEET;
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_transmitter_range_nm = 50; // arbitrary
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return;
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}
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// try the VORs next
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FGNav * nav = current_navlist->findByFreq(frequency_mhz,
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longitude_rad,
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latitude_rad,
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altitude_m);
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if (nav != 0)
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if (nav != 0 && nav->get_has_dme()) {
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_transmitter_valid = true;
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_transmitter = Point3D(nav->get_x(),
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nav->get_y(),
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nav->get_z());
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_transmitter_elevation_ft = nav->get_elev() * SG_METER_TO_FEET;
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_transmitter_range_nm = nav->get_range(); // fixme
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return;
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}
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_transmitter_valid = false;
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}
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// end of dme.cxx
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80
src/Instrumentation/dme.hxx
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80
src/Instrumentation/dme.hxx
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@ -0,0 +1,80 @@
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// dme.hxx - distance-measuring equipment.
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// Written by David Megginson, started 2003.
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//
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// This file is in the Public Domain and comes with no warranty.
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#ifndef __INSTRUMENTS_DME_HXX
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#define __INSTRUMENTS_DME_HXX 1
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#ifndef __cplusplus
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# error This library requires C++
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#endif
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#include <simgear/math/point3d.hxx>
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#include <simgear/misc/props.hxx>
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#include <Main/fgfs.hxx>
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/**
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* Model a DME radio.
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*
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* Input properties:
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*
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* /position/longitude-deg
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* /position/latitude-deg
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* /position/altitude-ft
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* /systems/electrical/outputs/dme
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* /instrumentation/dme/serviceable
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* /instrumentation/dme/frequencies/source
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* /instrumentation/dme/frequencies/selected-mhz
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*
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* Output properties:
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*
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* /instrumentation/dme/in-range
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* /instrumentation/dme/indicated-distance-nm
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* /instrumentation/dme/indicated-ground-speed-kt
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* /instrumentation/dme/indicated-time-kt
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*/
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class DME : public FGSubsystem
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{
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public:
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DME ();
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virtual ~DME ();
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virtual void init ();
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virtual void update (double delta_time_sec);
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private:
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void search (double frequency, double longitude_rad,
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double latitude_rad, double altitude_m);
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SGPropertyNode_ptr _longitude_node;
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SGPropertyNode_ptr _latitude_node;
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SGPropertyNode_ptr _altitude_node;
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SGPropertyNode_ptr _serviceable_node;
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SGPropertyNode_ptr _electrical_node;
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SGPropertyNode_ptr _source_node;
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SGPropertyNode_ptr _frequency_node;
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SGPropertyNode_ptr _in_range_node;
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SGPropertyNode_ptr _distance_node;
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SGPropertyNode_ptr _speed_node;
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SGPropertyNode_ptr _time_node;
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double _last_distance_nm;
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double _last_frequency_mhz;
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double _time_before_search_sec;
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bool _transmitter_valid;
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Point3D _transmitter;
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double _transmitter_elevation_ft;
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double _transmitter_range_nm;
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};
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#endif // __INSTRUMENTS_DME_HXX
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#include "heading_indicator.hxx"
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#include "vertical_speed_indicator.hxx"
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#include "mag_compass.hxx"
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#include "dme.hxx"
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FGInstrumentMgr::FGInstrumentMgr ()
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set_subsystem("hi", new HeadingIndicator);
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set_subsystem("vsi", new VerticalSpeedIndicator);
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set_subsystem("compass", new MagCompass);
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set_subsystem("dme", new DME, 1.0);
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}
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FGInstrumentMgr::~FGInstrumentMgr ()
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