/**************************************************************************** * * 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 "../ecl.h" #include "ekf.h" #include "mathlib.h" #include "geo.h" // GPS pre-flight check bit locations #define MASK_GPS_NSATS (1<<0) #define MASK_GPS_GDOP (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(uint64_t time_usec, struct gps_message *gps) { // Run GPS checks whenever the WGS-84 origin is not set or the vehicle is not using GPS // Also run checks if the vehicle is on-ground as the check data can be used by vehicle pre-flight checks if (!_control_status.flags.in_air || !_NED_origin_initialised || !_control_status.flags.gps) { bool gps_checks_pass = gps_is_good(gps); if (!_NED_origin_initialised && gps_checks_pass) { // If we have good GPS data set the origin's WGS-84 position to the last gps fix double lat = gps->lat / 1.0e7; double lon = gps->lon / 1.0e7; map_projection_init_timestamped(&_pos_ref, lat, lon, _time_last_imu); // if we are already doing aiding, corect for the change in posiiton since the EKF started navigating if (_control_status.flags.opt_flow || _control_status.flags.gps) { 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; _last_gps_origin_time_us = _time_last_imu; // set the magnetic declination returned by the geo library using the current GPS position _mag_declination_gps = math::radians(get_mag_declination(lat, lon)); // 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 (_primary_hgt_source == VDIST_SENSOR_GPS) { ECL_INFO("EKF GPS checks passed (WGS-84 origin set, using GPS height)"); _control_status.flags.baro_hgt = false; _control_status.flags.gps_hgt = true; _control_status.flags.rng_hgt = false; // zero the sensor offset _hgt_sensor_offset = 0.0f; } else { ECL_INFO("EKF 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(struct 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 geometric dilution of precision _gps_check_fail_status.flags.gdop = (gps->gdop > _params.req_gdop); // Check the reported horizontal position accuracy _gps_check_fail_status.flags.hacc = (gps->eph > _params.req_hacc); // Check the reported vertical position accuracy _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); // Calculate position movement since last measurement float delta_posN = 0.0f; float delta_PosE = 0.0f; double lat = gps->lat * 1.0e-7; double lon = gps->lon * 1.0e-7; // calculate position movement since last GPS fix if (_gps_pos_prev.timestamp > 0) { map_projection_project(&_gps_pos_prev, lat, lon, &delta_posN, &delta_PosE); } 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 time lapsed since last update, limit to prevent numerical errors and calculate the lowpass filter coefficient const float filt_time_const = 10.0f; float dt = fminf(fmaxf(float(_time_last_imu - _gps_pos_prev.timestamp) * 1e-6f, 0.001f), filt_time_const); float filter_coef = dt / filt_time_const; // save GPS fix for next time map_projection_init_timestamped(&_gps_pos_prev, lat, lon, _time_last_imu); // Calculate the horizontal drift velocity components and limit to 10x the threshold float vel_limit = 10.0f * _params.req_hdrift; float velN = fminf(fmaxf(delta_posN / dt, -vel_limit), vel_limit); float velE = fminf(fmaxf(delta_PosE / dt, -vel_limit), vel_limit); // Apply a low pass filter _gpsDriftVelN = velN * filter_coef + _gpsDriftVelN * (1.0f - filter_coef); _gpsDriftVelE = velE * filter_coef + _gpsDriftVelE * (1.0f - filter_coef); // Calculate the horizontal drift speed and fail if too high // This check can only be used if the vehicle is stationary during alignment if (!_control_status.flags.in_air) { float drift_speed = sqrtf(_gpsDriftVelN * _gpsDriftVelN + _gpsDriftVelE * _gpsDriftVelE); _gps_check_fail_status.flags.hdrift = (drift_speed > _params.req_hdrift); } else { _gps_check_fail_status.flags.hdrift = false; } // Calculate the vertical drift velocity and limit to 10x the threshold vel_limit = 10.0f * _params.req_vdrift; float gps_alt_m = 1e-3f * (float)gps->alt; float velD = math::constrain(((_gps_alt_prev - gps_alt_m) / dt), -vel_limit, vel_limit); _gps_alt_prev = gps_alt_m; // Apply a low pass filter to the vertical velocity _gps_drift_velD = velD * filter_coef + _gps_drift_velD * (1.0f - filter_coef); // Fail if the vertical drift speed is too high // This check can only be used if the vehicle is stationary during alignment if (!_control_status.flags.in_air) { _gps_check_fail_status.flags.vdrift = (fabsf(_gps_drift_velD) > _params.req_vdrift); } else { _gps_check_fail_status.flags.vdrift = false; } // Check the magnitude of the filtered horizontal GPS velocity // This check can only be used if the vehicle is stationary during alignment if (!_control_status.flags.in_air) { vel_limit = 10.0f * _params.req_hdrift; float gps_velN = fminf(fmaxf(gps->vel_ned[0], -vel_limit), vel_limit); float gps_velE = fminf(fmaxf(gps->vel_ned[1], -vel_limit), vel_limit); _gps_velN_filt = gps_velN * filter_coef + _gps_velN_filt * (1.0f - filter_coef); _gps_velE_filt = gps_velE * filter_coef + _gps_velE_filt * (1.0f - filter_coef); float horiz_speed = sqrtf(_gps_velN_filt * _gps_velN_filt + _gps_velE_filt * _gps_velE_filt); _gps_check_fail_status.flags.hspeed = (horiz_speed > _params.req_hdrift); } else { _gps_check_fail_status.flags.hspeed = false; } // Check the filtered difference between GPS and EKF vertical velocity vel_limit = 10.0f * _params.req_vdrift; float vertVel = fminf(fmaxf((gps->vel_ned[2] - _state.vel(2)), -vel_limit), vel_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.gdop && (_params.gps_check_mask & MASK_GPS_GDOP)) || (_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; } // continuous period without fail of 10 seconds required to return a healthy status return (_time_last_imu - _last_gps_fail_us > 1e7); }