/**************************************************************************** * * Copyright (c) 2013 Estimation and Control Library (ECL). All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in * the documentation and/or other materials provided with the * distribution. * 3. Neither the name ECL nor the names of its contributors may be * used to endorse or promote products derived from this software * without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE * POSSIBILITY OF SUCH DAMAGE. * ****************************************************************************/ /** * @file gps_checks.cpp * Perform pre-flight and in-flight GPS quality checks * * @author Paul Riseborough * */ #include "ekf.h" #include #include #include // GPS pre-flight check bit locations #define MASK_GPS_NSATS (1<<0) #define MASK_GPS_PDOP (1<<1) #define MASK_GPS_HACC (1<<2) #define MASK_GPS_VACC (1<<3) #define MASK_GPS_SACC (1<<4) #define MASK_GPS_HDRIFT (1<<5) #define MASK_GPS_VDRIFT (1<<6) #define MASK_GPS_HSPD (1<<7) #define MASK_GPS_VSPD (1<<8) bool Ekf::collect_gps(const gps_message &gps) { // Run GPS checks always _gps_checks_passed = gps_is_good(gps); if (!_NED_origin_initialised && _gps_checks_passed) { // If we have good GPS data set the origin's WGS-84 position to the last gps fix const double lat = gps.lat / 1.0e7; const double lon = gps.lon / 1.0e7; map_projection_init_timestamped(&_pos_ref, lat, lon, _time_last_imu); // if we are already doing aiding, correct for the change in position since the EKF started navigationg if (_control_status.flags.opt_flow || _control_status.flags.gps || _control_status.flags.ev_pos || _control_status.flags.ev_vel) { double est_lat, est_lon; map_projection_reproject(&_pos_ref, -_state.pos(0), -_state.pos(1), &est_lat, &est_lon); map_projection_init_timestamped(&_pos_ref, est_lat, est_lon, _time_last_imu); } // Take the current GPS height and subtract the filter height above origin to estimate the GPS height of the origin _gps_alt_ref = 1e-3f * (float)gps.alt + _state.pos(2); _NED_origin_initialised = true; _earth_rate_NED = calcEarthRateNED((float)_pos_ref.lat_rad); _last_gps_origin_time_us = _time_last_imu; // set the magnetic field data returned by the geo library using the current GPS position _mag_declination_gps = math::radians(get_mag_declination(lat, lon)); _mag_inclination_gps = math::radians(get_mag_inclination(lat, lon)); _mag_strength_gps = 0.01f * get_mag_strength(lat, lon); // request a reset of the yaw using the new declination _mag_yaw_reset_req = true; // save the horizontal and vertical position uncertainty of the origin _gps_origin_eph = gps.eph; _gps_origin_epv = gps.epv; // if the user has selected GPS as the primary height source, switch across to using it if (_params.vdist_sensor_type == VDIST_SENSOR_GPS) { ECL_INFO_TIMESTAMPED("GPS checks passed (WGS-84 origin set, using GPS height)"); setControlGPSHeight(); // zero the sensor offset _hgt_sensor_offset = 0.0f; } else { ECL_INFO_TIMESTAMPED("GPS checks passed (WGS-84 origin set)"); } } // start collecting GPS if there is a 3D fix and the NED origin has been set return _NED_origin_initialised && (gps.fix_type >= 3); } /* * Return true if the GPS solution quality is adequate to set an origin for the EKF * and start GPS aiding. * All activated checks must pass for 10 seconds. * Checks are activated using the EKF2_GPS_CHECK bitmask parameter * Checks are adjusted using the EKF2_REQ_* parameters */ bool Ekf::gps_is_good(const gps_message &gps) { // Check the fix type _gps_check_fail_status.flags.fix = (gps.fix_type < 3); // Check the number of satellites _gps_check_fail_status.flags.nsats = (gps.nsats < _params.req_nsats); // Check the position dilution of precision _gps_check_fail_status.flags.pdop = (gps.pdop > _params.req_pdop); // Check the reported horizontal and vertical position accuracy _gps_check_fail_status.flags.hacc = (gps.eph > _params.req_hacc); _gps_check_fail_status.flags.vacc = (gps.epv > _params.req_vacc); // Check the reported speed accuracy _gps_check_fail_status.flags.sacc = (gps.sacc > _params.req_sacc); // check if GPS quality is degraded _gps_error_norm = fmaxf((gps.eph / _params.req_hacc) , (gps.epv / _params.req_vacc)); _gps_error_norm = fmaxf(_gps_error_norm , (gps.sacc / _params.req_sacc)); // Calculate time lapsed since last update, limit to prevent numerical errors and calculate a lowpass filter coefficient const float filt_time_const = 10.0f; const float dt = fminf(fmaxf(float(_time_last_imu - _gps_pos_prev.timestamp) * 1e-6f, 0.001f), filt_time_const); const float filter_coef = dt / filt_time_const; // The following checks are only valid when the vehicle is at rest const double lat = gps.lat * 1.0e-7; const double lon = gps.lon * 1.0e-7; if (!_control_status.flags.in_air && _vehicle_at_rest) { // Calculate position movement since last measurement float delta_pos_n = 0.0f; float delta_pos_e = 0.0f; // calculate position movement since last GPS fix if (_gps_pos_prev.timestamp > 0) { map_projection_project(&_gps_pos_prev, lat, lon, &delta_pos_n, &delta_pos_e); } else { // no previous position has been set map_projection_init_timestamped(&_gps_pos_prev, lat, lon, _time_last_imu); _gps_alt_prev = 1e-3f * (float)gps.alt; } // Calculate the horizontal and vertical drift velocity components and limit to 10x the threshold const Vector3f vel_limit(_params.req_hdrift, _params.req_hdrift, _params.req_vdrift); Vector3f pos_derived(delta_pos_n, delta_pos_e, (_gps_alt_prev - 1e-3f * (float)gps.alt)); pos_derived = matrix::constrain(pos_derived / dt, -10.0f * vel_limit, 10.0f * vel_limit); // Apply a low pass filter _gps_pos_deriv_filt = pos_derived * filter_coef + _gps_pos_deriv_filt * (1.0f - filter_coef); // Calculate the horizontal drift speed and fail if too high _gps_drift_metrics[0] = Vector2f(_gps_pos_deriv_filt.xy()).norm(); _gps_check_fail_status.flags.hdrift = (_gps_drift_metrics[0] > _params.req_hdrift); // Fail if the vertical drift speed is too high _gps_drift_metrics[1] = fabsf(_gps_pos_deriv_filt(2)); _gps_check_fail_status.flags.vdrift = (_gps_drift_metrics[1] > _params.req_vdrift); // Check the magnitude of the filtered horizontal GPS velocity Vector2f gps_velNE = matrix::constrain(Vector2f(gps.vel_ned.xy()), -10.0f * _params.req_hdrift, 10.0f * _params.req_hdrift); _gps_velNE_filt = gps_velNE * filter_coef + _gps_velNE_filt * (1.0f - filter_coef); _gps_drift_metrics[2] = _gps_velNE_filt.norm(); _gps_check_fail_status.flags.hspeed = (_gps_drift_metrics[2] > _params.req_hdrift); _gps_drift_updated = true; } else if (_control_status.flags.in_air) { // These checks are always declared as passed when flying // If on ground and moving, the last result before movement commenced is kept _gps_check_fail_status.flags.hdrift = false; _gps_check_fail_status.flags.vdrift = false; _gps_check_fail_status.flags.hspeed = false; _gps_drift_updated = false; } else { // This is the case where the vehicle is on ground and IMU movement is blocking the drift calculation _gps_drift_updated = true; } // save GPS fix for next time map_projection_init_timestamped(&_gps_pos_prev, lat, lon, _time_last_imu); _gps_alt_prev = 1e-3f * (float)gps.alt; // Check the filtered difference between GPS and EKF vertical velocity float vz_diff_limit = 10.0f * _params.req_vdrift; float vertVel = fminf(fmaxf((gps.vel_ned(2) - _state.vel(2)), -vz_diff_limit), vz_diff_limit); _gps_velD_diff_filt = vertVel * filter_coef + _gps_velD_diff_filt * (1.0f - filter_coef); _gps_check_fail_status.flags.vspeed = (fabsf(_gps_velD_diff_filt) > _params.req_vdrift); // assume failed first time through if (_last_gps_fail_us == 0) { _last_gps_fail_us = _time_last_imu; } // if any user selected checks have failed, record the fail time if ( _gps_check_fail_status.flags.fix || (_gps_check_fail_status.flags.nsats && (_params.gps_check_mask & MASK_GPS_NSATS)) || (_gps_check_fail_status.flags.pdop && (_params.gps_check_mask & MASK_GPS_PDOP)) || (_gps_check_fail_status.flags.hacc && (_params.gps_check_mask & MASK_GPS_HACC)) || (_gps_check_fail_status.flags.vacc && (_params.gps_check_mask & MASK_GPS_VACC)) || (_gps_check_fail_status.flags.sacc && (_params.gps_check_mask & MASK_GPS_SACC)) || (_gps_check_fail_status.flags.hdrift && (_params.gps_check_mask & MASK_GPS_HDRIFT)) || (_gps_check_fail_status.flags.vdrift && (_params.gps_check_mask & MASK_GPS_VDRIFT)) || (_gps_check_fail_status.flags.hspeed && (_params.gps_check_mask & MASK_GPS_HSPD)) || (_gps_check_fail_status.flags.vspeed && (_params.gps_check_mask & MASK_GPS_VSPD)) ) { _last_gps_fail_us = _time_last_imu; } else { _last_gps_pass_us = _time_last_imu; } // continuous period without fail of x seconds required to return a healthy status return _time_last_imu - _last_gps_fail_us > (uint64_t)_min_gps_health_time_us; }