X-Git-Url: https://git.mxchange.org/?a=blobdiff_plain;f=src%2FInstrumentation%2Fgps.cxx;h=913aba769ad969de3ac368b9a1fa9f9f0316f7c3;hb=c6045147544badd6daefdcab9d4de1ed6936533b;hp=e5c040bb386427a0b087bd74a3be61eadd2ed0e0;hpb=439a9fa1e40ca9a1a30ef575fc31a433d080d9a1;p=flightgear.git diff --git a/src/Instrumentation/gps.cxx b/src/Instrumentation/gps.cxx index e5c040bb3..913aba769 100644 --- a/src/Instrumentation/gps.cxx +++ b/src/Instrumentation/gps.cxx @@ -3,20 +3,76 @@ // // This file is in the Public Domain and comes with no warranty. +#ifdef HAVE_CONFIG_H +# include +#endif + +#include "gps.hxx" + #include -#include +#include +#include "Main/fg_props.hxx" +#include "Main/util.hxx" // for fgLowPass +#include "Navaids/positioned.hxx" + +#include +#include #include -#include
+using std::string; -#include "gps.hxx" + +void SGGeodProperty::init(SGPropertyNode* base, const char* lonStr, const char* latStr, const char* altStr) +{ + _lon = base->getChild(lonStr, 0, true); + _lat = base->getChild(latStr, 0, true); + if (altStr) { + _alt = base->getChild(altStr, 0, true); + } +} + +void SGGeodProperty::init(const char* lonStr, const char* latStr, const char* altStr) +{ + _lon = fgGetNode(lonStr, true); + _lat = fgGetNode(latStr, true); + if (altStr) { + _alt = fgGetNode(altStr, true); + } +} + +void SGGeodProperty::clear() +{ + _lon = _lat = _alt = NULL; +} +void SGGeodProperty::operator=(const SGGeod& geod) +{ + _lon->setDoubleValue(geod.getLongitudeDeg()); + _lat->setDoubleValue(geod.getLatitudeDeg()); + if (_alt) { + _alt->setDoubleValue(geod.getElevationFt()); + } +} + +SGGeod SGGeodProperty::get() const +{ + double lon = _lon->getDoubleValue(), + lat = _lat->getDoubleValue(); + if (_alt) { + return SGGeod::fromDegFt(lon, lat, _alt->getDoubleValue()); + } else { + return SGGeod::fromDeg(lon,lat); + } +} -GPS::GPS () + +GPS::GPS ( SGPropertyNode *node) : _last_valid(false), - _last_longitude_deg(0), - _last_latitude_deg(0), - _last_altitude_m(0) + _alt_dist_ratio(0), + _distance_m(0), + _course_deg(0), + _name(node->getStringValue("name", "gps")), + _num(node->getIntValue("number", 0)) { } @@ -27,81 +83,521 @@ GPS::~GPS () void GPS::init () { - _longitude_node = fgGetNode("/position/longitude-deg", true); - _latitude_node = fgGetNode("/position/latitude-deg", true); - _altitude_node = fgGetNode("/position/altitude-ft", true); + string branch; + branch = "/instrumentation/" + _name; + + SGPropertyNode *node = fgGetNode(branch.c_str(), _num, true ); + _position.init("/position/longitude-deg", "/position/latitude-deg", "/position/altitude-ft"); _magvar_node = fgGetNode("/environment/magnetic-variation-deg", true); - _serviceable_node = fgGetNode("/instrumentation/gps/serviceable", true); + _serviceable_node = node->getChild("serviceable", 0, true); _electrical_node = fgGetNode("/systems/electrical/outputs/gps", true); - _raim_node = fgGetNode("/instrumentation/gps/raim", true); - _indicated_longitude_node = - fgGetNode("/instrumentation/gps/indicated-longitude-deg", true); - _indicated_latitude_node = - fgGetNode("/instrumentation/gps/indicated-latitude-deg", true); - _indicated_altitude_node = - fgGetNode("/instrumentation/gps/indicated-altitude-ft", true); + SGPropertyNode *wp_node = node->getChild("wp", 0, true); + SGPropertyNode *wp0_node = wp_node->getChild("wp", 0, true); + SGPropertyNode *wp1_node = wp_node->getChild("wp", 1, true); + + _wp0_position.init(wp0_node, "longitude-deg", "latitude-deg", "altitude-ft"); + _wp0_ID_node = wp0_node->getChild("ID", 0, true); + _wp0_name_node = wp0_node->getChild("name", 0, true); + _wp0_course_node = wp0_node->getChild("desired-course-deg", 0, true); + _wp0_distance_node = wp0_node->getChild("distance-nm", 0, true); + _wp0_ttw_node = wp0_node->getChild("TTW", 0, true); + _wp0_bearing_node = wp0_node->getChild("bearing-true-deg", 0, true); + _wp0_mag_bearing_node = wp0_node->getChild("bearing-mag-deg", 0, true); + _wp0_course_deviation_node = + wp0_node->getChild("course-deviation-deg", 0, true); + _wp0_course_error_nm_node = wp0_node->getChild("course-error-nm", 0, true); + _wp0_to_flag_node = wp0_node->getChild("to-flag", 0, true); + _true_wp0_bearing_error_node = + wp0_node->getChild("true-bearing-error-deg", 0, true); + _magnetic_wp0_bearing_error_node = + wp0_node->getChild("magnetic-bearing-error-deg", 0, true); + + _wp1_position.init(wp1_node, "longitude-deg", "latitude-deg", "altitude-ft"); + _wp1_ID_node = wp1_node->getChild("ID", 0, true); + _wp1_name_node = wp1_node->getChild("name", 0, true); + _wp1_course_node = wp1_node->getChild("desired-course-deg", 0, true); + _wp1_distance_node = wp1_node->getChild("distance-nm", 0, true); + _wp1_ttw_node = wp1_node->getChild("TTW", 0, true); + _wp1_bearing_node = wp1_node->getChild("bearing-true-deg", 0, true); + _wp1_mag_bearing_node = wp1_node->getChild("bearing-mag-deg", 0, true); + _wp1_course_deviation_node = + wp1_node->getChild("course-deviation-deg", 0, true); + _wp1_course_error_nm_node = wp1_node->getChild("course-error-nm", 0, true); + _wp1_to_flag_node = wp1_node->getChild("to-flag", 0, true); + _true_wp1_bearing_error_node = + wp1_node->getChild("true-bearing-error-deg", 0, true); + _magnetic_wp1_bearing_error_node = + wp1_node->getChild("magnetic-bearing-error-deg", 0, true); + _get_nearest_airport_node = + wp1_node->getChild("get-nearest-airport", 0, true); + + _tracking_bug_node = node->getChild("tracking-bug", 0, true); + _raim_node = node->getChild("raim", 0, true); + + _indicated_pos.init(node, "indicated-longitude-deg", + "indicated-latitude-deg", "indicated-altitude-ft"); + + _indicated_vertical_speed_node = + node->getChild("indicated-vertical-speed", 0, true); _true_track_node = - fgGetNode("/instrumentation/gps/indicated-track-true-deg", true); + node->getChild("indicated-track-true-deg", 0, true); _magnetic_track_node = - fgGetNode("/instrumentation/gps/indicated-track-magnetic-deg", true); + node->getChild("indicated-track-magnetic-deg", 0, true); _speed_node = - fgGetNode("/instrumentation/gps/indicated-ground-speed-kt", true); + node->getChild("indicated-ground-speed-kt", 0, true); + _odometer_node = + node->getChild("odometer", 0, true); + _trip_odometer_node = + node->getChild("trip-odometer", 0, true); + _true_bug_error_node = + node->getChild("true-bug-error-deg", 0, true); + _magnetic_bug_error_node = + node->getChild("magnetic-bug-error-deg", 0, true); + + _leg_distance_node = + wp_node->getChild("leg-distance-nm", 0, true); + _leg_course_node = + wp_node->getChild("leg-true-course-deg", 0, true); + _leg_magnetic_course_node = + wp_node->getChild("leg-mag-course-deg", 0, true); + _alt_dist_ratio_node = + wp_node->getChild("alt-dist-ratio", 0, true); + _leg_course_deviation_node = + wp_node->getChild("leg-course-deviation-deg", 0, true); + _leg_course_error_nm_node = + wp_node->getChild("leg-course-error-nm", 0, true); + _leg_to_flag_node = + wp_node->getChild("leg-to-flag", 0, true); + _alt_deviation_node = + wp_node->getChild("alt-deviation-ft", 0, true); + + _serviceable_node->setBoolValue(true); +} + +void +GPS::clearOutput() +{ + _last_valid = false; + _last_speed_kts = 0; + _last_pos = SGGeod(); + _raim_node->setDoubleValue(false); + _indicated_pos = SGGeod(); + _indicated_vertical_speed_node->setDoubleValue(0); + _true_track_node->setDoubleValue(0); + _magnetic_track_node->setDoubleValue(0); + _speed_node->setDoubleValue(0); + _wp1_distance_node->setDoubleValue(0); + _wp1_bearing_node->setDoubleValue(0); + _wp1_position = SGGeod(); + _wp1_course_node->setDoubleValue(0); + _odometer_node->setDoubleValue(0); + _trip_odometer_node->setDoubleValue(0); + _tracking_bug_node->setDoubleValue(0); + _true_bug_error_node->setDoubleValue(0); + _magnetic_bug_error_node->setDoubleValue(0); + _true_wp1_bearing_error_node->setDoubleValue(0); + _magnetic_wp1_bearing_error_node->setDoubleValue(0); } void GPS::update (double delta_time_sec) { - // If it's off, don't bother. - if (!_serviceable_node->getBoolValue() || - !_electrical_node->getBoolValue()) { - _last_valid = false; - _last_longitude_deg = 0; - _last_latitude_deg = 0; - _last_altitude_m = 0; - _raim_node->setDoubleValue(false); - _indicated_longitude_node->setDoubleValue(0); - _indicated_latitude_node->setDoubleValue(0); - _indicated_altitude_node->setDoubleValue(0); - _true_track_node->setDoubleValue(0); - _magnetic_track_node->setDoubleValue(0); - _speed_node->setDoubleValue(0); + // If it's off, don't bother. + if (!_serviceable_node->getBoolValue() || !_electrical_node->getBoolValue()) { + clearOutput(); return; } - // Get the aircraft position - double longitude_deg = _longitude_node->getDoubleValue(); - double latitude_deg = _latitude_node->getDoubleValue(); - double altitude_m = _altitude_node->getDoubleValue() * SG_FEET_TO_METER; - double magvar_deg = _magvar_node->getDoubleValue(); + UpdateContext ctx; + ctx.dt = delta_time_sec; + ctx.waypoint_changed = false; + ctx.pos = _position.get(); + + // TODO: Add noise and other errors. +/* + + // Bias and random error + double random_factor = sg_random(); + double random_error = 1.4; + double error_radius = 5.1; + double bias_max_radius = 5.1; + double random_max_radius = 1.4; + + bias_length += (random_factor-0.5) * 1.0e-3; + if (bias_length <= 0.0) bias_length = 0.0; + else if (bias_length >= bias_max_radius) bias_length = bias_max_radius; + bias_angle += (random_factor-0.5) * 1.0e-3; + if (bias_angle <= 0.0) bias_angle = 0.0; + else if (bias_angle >= 360.0) bias_angle = 360.0; + + double random_length = random_factor * random_max_radius; + double random_angle = random_factor * 360.0; + + double bias_x = bias_length * cos(bias_angle * SG_PI / 180.0); + double bias_y = bias_length * sin(bias_angle * SG_PI / 180.0); + double random_x = random_length * cos(random_angle * SG_PI / 180.0); + double random_y = random_length * sin(random_angle * SG_PI / 180.0); + double error_x = bias_x + random_x; + double error_y = bias_y + random_y; + double error_length = sqrt(error_x*error_x + error_y*error_y); + double error_angle = atan(error_y / error_x) * 180.0 / SG_PI; + double lat2; + double lon2; + double az2; + geo_direct_wgs_84 ( altitude_m, latitude_deg, + longitude_deg, error_angle, + error_length, &lat2, &lon2, + &az2 ); + //cout << lat2 << " " << lon2 << endl; + printf("%f %f \n", bias_length, bias_angle); + printf("%3.7f %3.7f \n", lat2, lon2); + printf("%f %f \n", error_length, error_angle); + +*/ _raim_node->setBoolValue(true); - _indicated_longitude_node->setDoubleValue(longitude_deg); - _indicated_latitude_node->setDoubleValue(latitude_deg); - _indicated_altitude_node->setDoubleValue(altitude_m * SG_METER_TO_FEET); + _indicated_pos = ctx.pos; if (_last_valid) { - double track1_deg, track2_deg, distance_m; - geo_inverse_wgs_84(altitude_m, - _last_latitude_deg, _last_longitude_deg, - latitude_deg, longitude_deg, - &track1_deg, &track2_deg, &distance_m); - double distance_nm = distance_m * SG_METER_TO_NM; - double speed_kt = ((distance_m * SG_METER_TO_NM) * - ((1 / delta_time_sec) * 3600.0)); - _true_track_node->setDoubleValue(track1_deg); - _magnetic_track_node->setDoubleValue(track1_deg - magvar_deg); - _speed_node->setDoubleValue(speed_kt); + updateWithValid(ctx); } else { - _true_track_node->setDoubleValue(0); - _magnetic_track_node->setDoubleValue(0); - _speed_node->setDoubleValue(0); + _true_track_node->setDoubleValue(0.0); + _magnetic_track_node->setDoubleValue(0.0); + _speed_node->setDoubleValue(0.0); + _last_valid = true; } - _last_valid = true; - _last_longitude_deg = longitude_deg; - _last_latitude_deg = latitude_deg; - _last_altitude_m = altitude_m; + _last_pos = ctx.pos; +} + +void +GPS::updateNearestAirport(UpdateContext& ctx) +{ + if (!_get_nearest_airport_node->getBoolValue()) { + return; + } + + // If the get-nearest-airport-node is true. + // Get the nearest airport, and set it as waypoint 1. + + FGPositioned::TypeFilter aptFilter(FGPositioned::AIRPORT); + FGPositionedRef a = FGPositioned::findClosest(ctx.pos, 360.0, &aptFilter); + if (!a) { + return; + } + + _wp1_position = a->geod(); + _wp1_ID_node->setStringValue(a->ident().c_str()); + _wp1_name_node->setStringValue(a->name().c_str()); + _get_nearest_airport_node->setBoolValue(false); + _last_wp1_ID = a->ident(); // don't trigger updateWaypoint1(); + ctx.waypoint_changed = true; +} + +void +GPS::updateWithValid(UpdateContext& ctx) +{ + assert(_last_valid); + double distance_m; + SGGeodesy::inverse(_last_pos, ctx.pos, ctx.track1_deg, ctx.track2_deg, distance_m ); + + ctx.speed_kt = ((distance_m * SG_METER_TO_NM) * ((1 / ctx.dt) * 3600.0)); + + double vertical_speed_mpm = ((ctx.pos.getElevationM() - _last_pos.getElevationM()) * 60 / + ctx.dt); + _indicated_vertical_speed_node->setDoubleValue(vertical_speed_mpm * SG_METER_TO_FEET); + _true_track_node->setDoubleValue(ctx.track1_deg); + + ctx.magvar_deg = _magvar_node->getDoubleValue(); + double mag_track_bearing = ctx.track1_deg - ctx.magvar_deg; + SG_NORMALIZE_RANGE(mag_track_bearing, 0.0, 360.0); + _magnetic_track_node->setDoubleValue(mag_track_bearing); + ctx.speed_kt = fgGetLowPass(_last_speed_kts, ctx.speed_kt, ctx.dt/20.0); + _last_speed_kts = ctx.speed_kt; + _speed_node->setDoubleValue(ctx.speed_kt); + + double odometer = _odometer_node->getDoubleValue(); + _odometer_node->setDoubleValue(odometer + distance_m * SG_METER_TO_NM); + odometer = _trip_odometer_node->getDoubleValue(); + _trip_odometer_node->setDoubleValue(odometer + distance_m * SG_METER_TO_NM); + + updateNearestAirport(ctx); + updateWaypoint0(ctx); + updateWaypoint1(ctx); + + ctx.wp0_pos = _wp0_position.get(); + ctx.wp1_pos = _wp1_position.get(); + // if this flag is set, we need to recompute leg data, because either + // WP0 or WP1 has been updated + if (ctx.waypoint_changed) { + waypointChanged(ctx); + } + + ctx.wp0_course_deg = _wp0_course_node->getDoubleValue(); + ctx.wp1_course_deg = _wp1_course_node->getDoubleValue(); + + updateWaypoint0Course(ctx); + updateWaypoint1Course(ctx); + updateLegCourse(ctx); + + // Altitude deviation + //double desired_altitude_m = wp1_altitude_m + // + wp1_distance * _alt_dist_ratio; + //double altitude_deviation_m = altitude_m - desired_altitude_m; + // _alt_deviation_node->setDoubleValue(altitude_deviation_m * SG_METER_TO_FEET); + + updateTrackingBug(ctx); +} + +void +GPS::updateLegCourse(UpdateContext& ctx) +{ + // Leg course deviation is the diffenrence between the bearing + // and the course. + double course_deviation_deg = ctx.wp1_bearing_deg - _course_deg; + SG_NORMALIZE_RANGE(course_deviation_deg, -180.0, 180.0); + + // If the course deviation is less than 90 degrees to either side, + // our desired course is towards the waypoint. + // It does not matter if we are actually moving + // towards or from the waypoint. + if (fabs(course_deviation_deg) < 90.0) { + _leg_to_flag_node->setBoolValue(true); + } + // If it's more than 90 degrees the desired + // course is from the waypoint. + else if (fabs(course_deviation_deg) > 90.0) { + _leg_to_flag_node->setBoolValue(false); + // When the course is away from the waypoint, + // it makes sense to change the sign of the deviation. + course_deviation_deg *= -1.0; + SG_NORMALIZE_RANGE(course_deviation_deg, -90.0, 90.0); + } + + _leg_course_deviation_node->setDoubleValue(course_deviation_deg); + + // Cross track error. + double course_error_m = sin(course_deviation_deg * SG_PI / 180.0) + * (_distance_m); + _leg_course_error_nm_node->setDoubleValue(course_error_m * SG_METER_TO_NM); + +} + +void +GPS::updateTrackingBug(UpdateContext& ctx) +{ + double tracking_bug = _tracking_bug_node->getDoubleValue(); + double true_bug_error = tracking_bug - ctx.track1_deg; + double magnetic_bug_error = tracking_bug - _magnetic_track_node->getDoubleValue(); + + // Get the errors into the (-180,180) range. + SG_NORMALIZE_RANGE(true_bug_error, -180.0, 180.0); + SG_NORMALIZE_RANGE(magnetic_bug_error, -180.0, 180.0); + + _true_bug_error_node->setDoubleValue(true_bug_error); + _magnetic_bug_error_node->setDoubleValue(magnetic_bug_error); +} + +void +GPS::waypointChanged(UpdateContext& ctx) +{ + // If any of the two waypoints have changed + // we need to calculate a new course between them, + // and values for vertical navigation. + assert(ctx.waypoint_changed); + + double track2; + SGGeodesy::inverse(ctx.wp0_pos, ctx.wp1_pos, _course_deg, track2, _distance_m); + + double leg_mag_course = _course_deg - _magvar_node->getDoubleValue(); + SG_NORMALIZE_RANGE(leg_mag_course, 0.0, 360.0); + + // Get the altitude / distance ratio + if ( _distance_m > 0.0 ) { + double alt_difference_m = ctx.wp0_pos.getElevationM() - ctx.wp1_pos.getElevationM(); + _alt_dist_ratio = alt_difference_m / _distance_m; + } + + _leg_distance_node->setDoubleValue(_distance_m * SG_METER_TO_NM); + _leg_course_node->setDoubleValue(_course_deg); + _leg_magnetic_course_node->setDoubleValue(leg_mag_course); + _alt_dist_ratio_node->setDoubleValue(_alt_dist_ratio); +} + +void +GPS::updateWaypoint0(UpdateContext& ctx) +{ + string id(_wp0_ID_node->getStringValue()); + if (_last_wp0_ID == id) { + return; // easy, nothing to do + } + + FGPositionedRef result = FGPositioned::findClosestWithIdent(id, ctx.pos); + if (!result) { + // not found, hmm + _last_wp0_ID = id; + return; + } + + _wp0_position = result->geod(); + _wp0_name_node->setStringValue(result->name().c_str()); + _last_wp0_ID = id; + ctx.waypoint_changed = true; +} + +void +GPS::updateWaypoint1(UpdateContext& ctx) +{ + string id(_wp1_ID_node->getStringValue()); + if (_last_wp1_ID == id) { + return; // easy, nothing to do + } + + FGPositionedRef result = FGPositioned::findClosestWithIdent(id, ctx.pos); + if (!result) { + // not found, hmm + _last_wp1_ID = id; + return; + } + + _wp1_position = result->geod(); + _wp1_name_node->setStringValue(result->name().c_str()); + _last_wp1_ID = id; + ctx.waypoint_changed = true; +} + +void +GPS::updateTTWNode(UpdateContext& ctx, double distance_m, SGPropertyNode_ptr node) +{ + // Estimate time to waypoint. + // The estimation does not take track into consideration, + // so if you are going away from the waypoint the TTW will + // increase. Makes most sense when travelling directly towards + // the waypoint. + double TTW = 0.0; + if (ctx.speed_kt > 0.0 && distance_m > 0.0) { + TTW = (distance_m * SG_METER_TO_NM) / (ctx.speed_kt / 3600); + } + + unsigned int TTW_seconds = (int) (TTW + 0.5); + if (TTW_seconds < 356400) { // That's 99 hours + unsigned int TTW_minutes = 0; + unsigned int TTW_hours = 0; + char TTW_str[9]; + while (TTW_seconds >= 3600) { + TTW_seconds -= 3600; + TTW_hours++; + } + while (TTW_seconds >= 60) { + TTW_seconds -= 60; + TTW_minutes++; + } + snprintf(TTW_str, 9, "%02d:%02d:%02d", + TTW_hours, TTW_minutes, TTW_seconds); + node->setStringValue(TTW_str); + } else { + node->setStringValue("--:--:--"); + } +} + +void +GPS::updateWaypoint0Course(UpdateContext& ctx) +{ + // Find the bearing and distance to waypoint 0. + double az2; + SGGeodesy::inverse(ctx.pos, ctx.wp0_pos, ctx.wp0_bearing_deg, az2,ctx.wp0_distance); + _wp0_distance_node->setDoubleValue(ctx.wp0_distance * SG_METER_TO_NM); + _wp0_bearing_node->setDoubleValue(ctx.wp0_bearing_deg); + + double mag_bearing_deg = ctx.wp0_bearing_deg - ctx.magvar_deg; + SG_NORMALIZE_RANGE(mag_bearing_deg, 0.0, 360.0); + _wp0_mag_bearing_node->setDoubleValue(mag_bearing_deg); + double bearing_error_deg = ctx.track1_deg - ctx.wp0_bearing_deg; + SG_NORMALIZE_RANGE(bearing_error_deg, -180.0, 180.0); + _true_wp0_bearing_error_node->setDoubleValue(bearing_error_deg); + + updateTTWNode(ctx, ctx.wp0_distance, _wp0_ttw_node); + + // Course deviation is the diffenrence between the bearing + // and the course. + double course_deviation_deg = ctx.wp0_bearing_deg - + ctx.wp0_course_deg; + SG_NORMALIZE_RANGE(course_deviation_deg, -180.0, 180.0); + + // If the course deviation is less than 90 degrees to either side, + // our desired course is towards the waypoint. + // It does not matter if we are actually moving + // towards or from the waypoint. + if (fabs(course_deviation_deg) < 90.0) { + _wp0_to_flag_node->setBoolValue(true); + } + // If it's more than 90 degrees the desired + // course is from the waypoint. + else if (fabs(course_deviation_deg) > 90.0) { + _wp0_to_flag_node->setBoolValue(false); + // When the course is away from the waypoint, + // it makes sense to change the sign of the deviation. + course_deviation_deg *= -1.0; + SG_NORMALIZE_RANGE(course_deviation_deg, -90.0, 90.0); + } + + _wp0_course_deviation_node->setDoubleValue(course_deviation_deg); + + // Cross track error. + double course_error_m = sin(course_deviation_deg * SG_PI / 180.0) + * (ctx.wp0_distance); + _wp0_course_error_nm_node->setDoubleValue(course_error_m * SG_METER_TO_NM); +} + +void +GPS::updateWaypoint1Course(UpdateContext& ctx) +{ + // Find the bearing and distance to waypoint 0. + double az2; + SGGeodesy::inverse(ctx.pos, ctx.wp1_pos, ctx.wp1_bearing_deg, az2,ctx.wp1_distance); + _wp1_distance_node->setDoubleValue(ctx.wp1_distance * SG_METER_TO_NM); + _wp1_bearing_node->setDoubleValue(ctx.wp1_bearing_deg); + + double mag_bearing_deg = ctx.wp1_bearing_deg - ctx.magvar_deg; + SG_NORMALIZE_RANGE(mag_bearing_deg, 0.0, 360.0); + _wp1_mag_bearing_node->setDoubleValue(mag_bearing_deg); + double bearing_error_deg = ctx.track1_deg - ctx.wp1_bearing_deg; + SG_NORMALIZE_RANGE(bearing_error_deg, -180.0, 180.0); + _true_wp1_bearing_error_node->setDoubleValue(bearing_error_deg); + + updateTTWNode(ctx, ctx.wp1_distance, _wp1_ttw_node); + + // Course deviation is the diffenrence between the bearing + // and the course. + double course_deviation_deg = ctx.wp1_bearing_deg - + ctx.wp1_course_deg; + SG_NORMALIZE_RANGE(course_deviation_deg, -180.0, 180.0); + + // If the course deviation is less than 90 degrees to either side, + // our desired course is towards the waypoint. + // It does not matter if we are actually moving + // towards or from the waypoint. + if (fabs(course_deviation_deg) < 90.0) { + _wp1_to_flag_node->setBoolValue(true); + } + // If it's more than 90 degrees the desired + // course is from the waypoint. + else if (fabs(course_deviation_deg) > 90.0) { + _wp1_to_flag_node->setBoolValue(false); + // When the course is away from the waypoint, + // it makes sense to change the sign of the deviation. + course_deviation_deg *= -1.0; + SG_NORMALIZE_RANGE(course_deviation_deg, -90.0, 90.0); + } + + _wp1_course_deviation_node->setDoubleValue(course_deviation_deg); + + // Cross track error. + double course_error_m = sin(course_deviation_deg * SG_PI / 180.0) + * (ctx.wp1_distance); + _wp1_course_error_nm_node->setDoubleValue(course_error_m * SG_METER_TO_NM); + } // end of gps.cxx