mirror of https://github.com/ArduPilot/ardupilot
202 lines
8.0 KiB
Plaintext
202 lines
8.0 KiB
Plaintext
/// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*-
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/**
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state of the vehicle we are tracking
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*/
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static struct {
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Location location; // lat, long in degrees * 10^7; alt in meters * 100
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uint32_t last_update_us;
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float heading; // degrees
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float ground_speed; // m/s
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} vehicle;
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/**
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update the pitch (elevation) servo. The aim is to drive the boards ahrs pitch to the
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requested pitch, so the board (and therefore the antenna) will be pointing at the target
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*/
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static void update_pitch_servo(float pitch)
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{
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// degrees(ahrs.pitch) is -90 to 90, where 0 is horizontal
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// pitch argument is -90 to 90, where 0 is horizontal
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// servo_out is in 100ths of a degree
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float ahrs_pitch = degrees(ahrs.pitch);
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int32_t err = (ahrs_pitch - pitch) * 100.0;
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// Need to configure your servo so that increasing servo_out causes increase in pitch/elevation (ie pointing higher into the sky,
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// above the horizon. On my antenna tracker this requires the pitch/elevation servo to be reversed
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// param set RC2_REV -1
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//
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// The pitch servo (RC channel 2) is configured for servo_out of -9000-0-9000 servo_out,
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// which will drive the servo from RC2_MIN to RC2_MAX usec pulse width.
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// Therefore, you must set RC2_MIN and RC2_MAX so that your servo drives the antenna altitude between -90 to 90 exactly
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// To drive my HS-645MG servos through their full 180 degrees of rotational range, I have to set:
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// param set RC2_MAX 2540
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// param set RC2_MIN 640
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//
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// You will also need to tune the pitch PID to suit your antenna and servos. I use:
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// PITCH2SRV_P 0.100000
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// PITCH2SRV_I 0.020000
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// PITCH2SRV_D 0.000000
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// PITCH2SRV_IMAX 4000.000000
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int32_t new_servo_out = channel_pitch.servo_out - g.pidPitch2Srv.get_pid(err);
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channel_pitch.servo_out = constrain_float(new_servo_out, -9000, 9000);
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channel_pitch.calc_pwm();
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channel_pitch.output();
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}
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/**
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update the yaw (azimuth) servo. The aim is to drive the boards ahrs yaw to the
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requested yaw, so the board (and therefore the antenna) will be pinting at the target
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*/
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static void update_yaw_servo(float yaw)
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{
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// degrees(ahrs.yaw) is -180 to 180, where 0 is north
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float ahrs_yaw = degrees(ahrs.yaw);
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// yaw argument is 0 to 360 where 0 and 360 are north
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// Make yaw -180-0-180 too
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if (yaw > 180)
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yaw = yaw - 360;
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// Antenna as Ballerina. Use with antenna that do not have continuously rotating servos, ie at some point in rotation
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// the servo limits are reached and the servo has to slew 360 degrees to the 'other side' to keep tracking.
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//
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// This algorithm accounts for the fact that the antenna mount may not be aligned with North
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// (in fact, any alignment is permissable), and that the alignment may change (possibly rapidly) over time
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// (as when the antenna is mounted on a moving, turning vehicle)
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// When the servo is being forced beyond its limits, it rapidly slews to the 'other side' then normal tracking takes over.
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//
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// Caution: this whole system is compromised by the fact that the ahrs_yaw reported by the compass system lags
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// the actual yaw by about 5 seconds, and also periodically realigns itself with about a 30 second period,
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// which makes it very hard to be completely sure exactly where the antenna is _really_ pointing
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// especially during the high speed slew. This can cause odd pointing artifacts from time to time. The best strategy is to
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// position and point the mount so the aircraft does not 'go behind' the antenna (if possible)
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//
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// With my antenna mount, large pwm output drives the antenna anticlockise, so need:
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// param set RC1_REV -1
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// to reverse the servo. Yours may be different
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//
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// You MUST set RC1_MIN and RC1_MAX so that your servo drives the antenna azimuth from -180 to 180 relative
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// to the mount.
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// To drive my HS-645MG servos through their full 180 degrees of rotational range and therefore the
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// antenna through a full 360 degrees, I have to set:
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// param set RC1_MAX 2380
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// param set RC1_MIN 680
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// According to the specs at https://www.servocity.com/html/hs-645mg_ultra_torque.html,
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// that should be 600 through 2400, but the azimuth gearing in my antenna pointer is not exactly 2:1
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int32_t err = (ahrs_yaw - yaw) * 100.0;
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static int32_t last_err = 0.0;
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// Correct for wrapping yaw at +-180
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// so we get the error to the _closest_ version of the target azimuth
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// +ve error requires anticlockwise motion (ie towards more negative yaw)
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if (err > 18000)
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err -= 36000;
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else if (err < -18000)
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err += 36000;
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static int32_t slew_to = 0;
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int32_t servo_err = channel_yaw.servo_out - err; // Servo position we need to get to
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if ( !slew_to
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&& servo_err > 19000 // 10 degreee deadband
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&& err < 0
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&& last_err > err)
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{
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// We need to be beyond the servo limits and the error magnitude is increasing
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// Slew most of the way to the other side at high speed...
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slew_to = servo_err - 27000;
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}
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else if ( !slew_to
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&& servo_err < -19000 // 10 degreee deadband
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&& err > 0
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&& last_err < err)
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{
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// We need to be beyond the servo limits and the error magnitude is increasing
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// Slew most of the way to the other side at high speed...
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slew_to = servo_err + 27000;
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}
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else if ( slew_to < 0
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&& err > 0
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&& last_err < err)
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{
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// ...then let normal tracking take over
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slew_to = 0;
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}
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else if ( slew_to > 0
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&& err < 0
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&& last_err > err)
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{
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// ...then let normal tracking take over
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slew_to = 0;
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}
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if (slew_to)
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{
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channel_yaw.servo_out = slew_to;
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}
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else
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{
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// Normal tracking
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// You will need to tune the yaw PID to suit your antenna and servos
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// For my servos, suitable PID settings are:
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// param set YAW2SRV_P 0.1
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// param set YAW2SRV_I 0.05
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// param set YAW2SRV_D 0
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// param set YAW2SRV_IMAX 4000
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int32_t new_servo_out = channel_yaw.servo_out - g.pidYaw2Srv.get_pid(err);
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channel_yaw.servo_out = constrain_float(new_servo_out, -18000, 18000);
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}
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last_err = err;
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channel_yaw.calc_pwm();
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channel_yaw.output();
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}
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/**
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main antenna tracking code, called at 50Hz
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*/
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static void update_tracking(void)
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{
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// project the vehicle position to take account of lost radio packets
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Location vpos = vehicle.location;
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float dt = (hal.scheduler->micros() - vehicle.last_update_us) * 1.0e-6f;
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location_update(vpos, vehicle.heading, vehicle.ground_speed * dt);
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// update our position if we have at least a 2D fix
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if (g_gps->status() >= GPS::GPS_OK_FIX_2D) {
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current_loc.lat = g_gps->latitude;
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current_loc.lng = g_gps->longitude;
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current_loc.alt = 0; // assume ground level for now REVISIT: WHY?
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}
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else {
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current_loc = home_loc; // dont know any better
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}
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// calculate the bearing to the vehicle
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float bearing = get_bearing_cd(current_loc, vehicle.location) * 0.01f;
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float distance = get_distance(current_loc, vehicle.location);
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float pitch = degrees(atan2((vehicle.location.alt - current_loc.alt)/100, distance));
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// update the servos
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update_pitch_servo(pitch);
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update_yaw_servo(bearing);
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// update nav_status for NAV_CONTROLLER_OUTPUT
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nav_status.bearing = bearing;
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nav_status.pitch = pitch;
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nav_status.distance = distance;
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}
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/**
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handle an updated position from the aircraft
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*/
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static void tracking_update_position(const mavlink_global_position_int_t &msg)
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{
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vehicle.location.lat = msg.lat;
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vehicle.location.lng = msg.lon;
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vehicle.location.alt = msg.relative_alt/10;
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vehicle.heading = msg.hdg * 0.01f;
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vehicle.ground_speed = pythagorous2(msg.vx, msg.vy) * 0.01f;
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vehicle.last_update_us = hal.scheduler->micros();
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}
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