path: root/src/modules/position_estimator_inav/position_estimator_inav_main.c

/****************************************************************************
 *
 *   Copyright (C) 2013, 2014 PX4 Development Team. 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 PX4 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
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 * 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 position_estimator_inav_main.c
 * Model-identification based position estimator for multirotors
 *
 * @author Anton Babushkin <anton.babushkin@me.com>
 */

#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <stdbool.h>
#include <fcntl.h>
#include <string.h>
#include <nuttx/config.h>
#include <nuttx/sched.h>
#include <sys/prctl.h>
#include <termios.h>
#include <math.h>
#include <float.h>
#include <uORB/uORB.h>
#include <uORB/topics/parameter_update.h>
#include <uORB/topics/actuator_controls.h>
#include <uORB/topics/actuator_armed.h>
#include <uORB/topics/sensor_combined.h>
#include <uORB/topics/vehicle_attitude.h>
#include <uORB/topics/vehicle_local_position.h>
#include <uORB/topics/vehicle_global_position.h>
#include <uORB/topics/vehicle_gps_position.h>
#include <uORB/topics/home_position.h>
#include <uORB/topics/optical_flow.h>
#include <mavlink/mavlink_log.h>
#include <poll.h>
#include <systemlib/err.h>
#include <geo/geo.h>
#include <systemlib/systemlib.h>
#include <drivers/drv_hrt.h>

#include "position_estimator_inav_params.h"
#include "inertial_filter.h"

#define MIN_VALID_W 0.00001f
#define PUB_INTERVAL 10000	// limit publish rate to 100 Hz
#define EST_BUF_SIZE 250000 / PUB_INTERVAL		// buffer size is 0.5s

static bool thread_should_exit = false; /**< Deamon exit flag */
static bool thread_running = false; /**< Deamon status flag */
static int position_estimator_inav_task; /**< Handle of deamon task / thread */
static bool verbose_mode = false;

static const hrt_abstime gps_topic_timeout = 500000;		// GPS topic timeout = 0.5s
static const hrt_abstime flow_topic_timeout = 1000000;	// optical flow topic timeout = 1s
static const hrt_abstime sonar_timeout = 150000;	// sonar timeout = 150ms
static const hrt_abstime sonar_valid_timeout = 1000000;	// estimate sonar distance during this time after sonar loss
static const hrt_abstime xy_src_timeout = 2000000;	// estimate position during this time after position sources loss
static const uint32_t updates_counter_len = 1000000;
static const float max_flow = 1.0f;	// max flow value that can be used, rad/s

__EXPORT int position_estimator_inav_main(int argc, char *argv[]);

int position_estimator_inav_thread_main(int argc, char *argv[]);

static void usage(const char *reason);

static inline int min(int val1, int val2)
{
	return (val1 < val2) ? val1 : val2;
}

static inline int max(int val1, int val2)
{
	return (val1 > val2) ? val1 : val2;
}

/**
 * Print the correct usage.
 */
static void usage(const char *reason)
{
	if (reason) {
		fprintf(stderr, "%s\n", reason);
	}

	fprintf(stderr, "usage: position_estimator_inav {start|stop|status} [-v]\n\n");
	exit(1);
}

/**
 * The position_estimator_inav_thread only briefly exists to start
 * the background job. The stack size assigned in the
 * Makefile does only apply to this management task.
 *
 * The actual stack size should be set in the call
 * to task_create().
 */
int position_estimator_inav_main(int argc, char *argv[])
{
	if (argc < 1) {
		usage("missing command");
	}

	if (!strcmp(argv[1], "start")) {
		if (thread_running) {
			warnx("already running");
			/* this is not an error */
			exit(0);
		}

		verbose_mode = false;

		if (argc > 1)
			if (!strcmp(argv[2], "-v")) {
				verbose_mode = true;
			}

		thread_should_exit = false;
		position_estimator_inav_task = task_spawn_cmd("position_estimator_inav",
					       SCHED_DEFAULT, SCHED_PRIORITY_MAX - 5, 5000,
					       position_estimator_inav_thread_main,
					       (argv) ? (const char **) &argv[2] : (const char **) NULL);
		exit(0);
	}

	if (!strcmp(argv[1], "stop")) {
		if (thread_running) {
			warnx("stop");
			thread_should_exit = true;

		} else {
			warnx("app not started");
		}

		exit(0);
	}

	if (!strcmp(argv[1], "status")) {
		if (thread_running) {
			warnx("app is running");

		} else {
			warnx("app not started");
		}

		exit(0);
	}

	usage("unrecognized command");
	exit(1);
}

static void write_debug_log(const char *msg, float dt, float x_est[2], float y_est[2], float z_est[2], float x_est_prev[2], float y_est_prev[2], float z_est_prev[2], float acc[3], float corr_gps[3][2], float w_xy_gps_p, float w_xy_gps_v)
{
	FILE *f = fopen("/fs/microsd/inav.log", "a");

	if (f) {
		char *s = malloc(256);
		unsigned n = snprintf(s, 256, "%llu %s\n\tdt=%.5f x_est=[%.5f %.5f] y_est=[%.5f %.5f] z_est=[%.5f %.5f] x_est_prev=[%.5f %.5f] y_est_prev=[%.5f %.5f] z_est_prev=[%.5f %.5f]\n",
                              hrt_absolute_time(), msg, (double)dt,
                              (double)x_est[0], (double)x_est[1], (double)y_est[0], (double)y_est[1], (double)z_est[0], (double)z_est[1],
                              (double)x_est_prev[0], (double)x_est_prev[1], (double)y_est_prev[0], (double)y_est_prev[1], (double)z_est_prev[0], (double)z_est_prev[1]);
		fwrite(s, 1, n, f);
		n = snprintf(s, 256, "\tacc=[%.5f %.5f %.5f] gps_pos_corr=[%.5f %.5f %.5f] gps_vel_corr=[%.5f %.5f %.5f] w_xy_gps_p=%.5f w_xy_gps_v=%.5f\n",
                     (double)acc[0], (double)acc[1], (double)acc[2],
                     (double)corr_gps[0][0], (double)corr_gps[1][0], (double)corr_gps[2][0], (double)corr_gps[0][1], (double)corr_gps[1][1], (double)corr_gps[2][1],
                     (double)w_xy_gps_p, (double)w_xy_gps_v);
		fwrite(s, 1, n, f);
		free(s);
	}

	fsync(fileno(f));
	fclose(f);
}

/****************************************************************************
 * main
 ****************************************************************************/
int position_estimator_inav_thread_main(int argc, char *argv[])
{
	warnx("started");
	int mavlink_fd;
	mavlink_fd = open(MAVLINK_LOG_DEVICE, 0);
	mavlink_log_info(mavlink_fd, "[inav] started");

	float x_est[2] = { 0.0f, 0.0f };	// pos, vel
	float y_est[2] = { 0.0f, 0.0f };	// pos, vel
	float z_est[2] = { 0.0f, 0.0f };	// pos, vel

	float est_buf[EST_BUF_SIZE][3][2];	// estimated position buffer
	float R_buf[EST_BUF_SIZE][3][3];	// rotation matrix buffer
	float R_gps[3][3];					// rotation matrix for GPS correction moment
	memset(est_buf, 0, sizeof(est_buf));
	memset(R_buf, 0, sizeof(R_buf));
	memset(R_gps, 0, sizeof(R_gps));
	int buf_ptr = 0;

	static const float min_eph_epv = 2.0f;	// min EPH/EPV, used for weight calculation
	static const float max_eph_epv = 20.0f;	// max EPH/EPV acceptable for estimation

	float eph = max_eph_epv;
	float epv = 1.0f;

	float eph_flow = 1.0f;

	float x_est_prev[2], y_est_prev[2], z_est_prev[2];
	memset(x_est_prev, 0, sizeof(x_est_prev));
	memset(y_est_prev, 0, sizeof(y_est_prev));
	memset(z_est_prev, 0, sizeof(z_est_prev));

	int baro_init_cnt = 0;
	int baro_init_num = 200;
	float baro_offset = 0.0f;		// baro offset for reference altitude, initialized on start, then adjusted
	float surface_offset = 0.0f;	// ground level offset from reference altitude
	float surface_offset_rate = 0.0f;	// surface offset change rate
	float alt_avg = 0.0f;
	bool landed = true;
	hrt_abstime landed_time = 0;

	hrt_abstime accel_timestamp = 0;
	hrt_abstime baro_timestamp = 0;

	bool ref_inited = false;
	hrt_abstime ref_init_start = 0;
	const hrt_abstime ref_init_delay = 1000000;	// wait for 1s after 3D fix
	struct map_projection_reference_s ref;
	memset(&ref, 0, sizeof(ref));
	hrt_abstime home_timestamp = 0;

	uint16_t accel_updates = 0;
	uint16_t baro_updates = 0;
	uint16_t gps_updates = 0;
	uint16_t attitude_updates = 0;
	uint16_t flow_updates = 0;

	hrt_abstime updates_counter_start = hrt_absolute_time();
	hrt_abstime pub_last = hrt_absolute_time();

	hrt_abstime t_prev = 0;

	/* store error when sensor updates, but correct on each time step to avoid jumps in estimated value */
	float acc[] = { 0.0f, 0.0f, 0.0f };	// N E D
	float acc_bias[] = { 0.0f, 0.0f, 0.0f };	// body frame
	float corr_baro = 0.0f;		// D
	float corr_gps[3][2] = {
		{ 0.0f, 0.0f },		// N (pos, vel)
		{ 0.0f, 0.0f },		// E (pos, vel)
		{ 0.0f, 0.0f },		// D (pos, vel)
	};
	float w_gps_xy = 1.0f;
	float w_gps_z = 1.0f;
	float corr_sonar = 0.0f;
	float corr_sonar_filtered = 0.0f;

	float corr_flow[] = { 0.0f, 0.0f };	// N E
	float w_flow = 0.0f;

	float sonar_prev = 0.0f;
	hrt_abstime flow_prev = 0;			// time of last flow measurement
	hrt_abstime sonar_time = 0;			// time of last sonar measurement (not filtered)
	hrt_abstime sonar_valid_time = 0;	// time of last sonar measurement used for correction (filtered)

	bool gps_valid = false;			// GPS is valid
	bool sonar_valid = false;		// sonar is valid
	bool flow_valid = false;		// flow is valid
	bool flow_accurate = false;		// flow should be accurate (this flag not updated if flow_valid == false)

	/* declare and safely initialize all structs */
	struct actuator_controls_s actuator;
	memset(&actuator, 0, sizeof(actuator));
	struct actuator_armed_s armed;
	memset(&armed, 0, sizeof(armed));
	struct sensor_combined_s sensor;
	memset(&sensor, 0, sizeof(sensor));
	struct vehicle_gps_position_s gps;
	memset(&gps, 0, sizeof(gps));
	struct home_position_s home;
	memset(&home, 0, sizeof(home));
	struct vehicle_attitude_s att;
	memset(&att, 0, sizeof(att));
	struct vehicle_local_position_s local_pos;
	memset(&local_pos, 0, sizeof(local_pos));
	struct optical_flow_s flow;
	memset(&flow, 0, sizeof(flow));
	struct vehicle_global_position_s global_pos;
	memset(&global_pos, 0, sizeof(global_pos));

	/* subscribe */
	int parameter_update_sub = orb_subscribe(ORB_ID(parameter_update));
	int actuator_sub = orb_subscribe(ORB_ID_VEHICLE_ATTITUDE_CONTROLS);
	int armed_sub = orb_subscribe(ORB_ID(actuator_armed));
	int sensor_combined_sub = orb_subscribe(ORB_ID(sensor_combined));
	int vehicle_attitude_sub = orb_subscribe(ORB_ID(vehicle_attitude));
	int optical_flow_sub = orb_subscribe(ORB_ID(optical_flow));
	int vehicle_gps_position_sub = orb_subscribe(ORB_ID(vehicle_gps_position));
	int home_position_sub = orb_subscribe(ORB_ID(home_position));

	/* advertise */
	orb_advert_t vehicle_local_position_pub = orb_advertise(ORB_ID(vehicle_local_position), &local_pos);
	orb_advert_t vehicle_global_position_pub = -1;

	struct position_estimator_inav_params params;
	struct position_estimator_inav_param_handles pos_inav_param_handles;
	/* initialize parameter handles */
	parameters_init(&pos_inav_param_handles);

	/* first parameters read at start up */
	struct parameter_update_s param_update;
	orb_copy(ORB_ID(parameter_update), parameter_update_sub, &param_update); /* read from param topic to clear updated flag */
	/* first parameters update */
	parameters_update(&pos_inav_param_handles, &params);

	struct pollfd fds_init[1] = {
		{ .fd = sensor_combined_sub, .events = POLLIN },
	};

	/* wait for initial baro value */
	bool wait_baro = true;

	thread_running = true;

	while (wait_baro && !thread_should_exit) {
		int ret = poll(fds_init, 1, 1000);

		if (ret < 0) {
			/* poll error */
			mavlink_log_info(mavlink_fd, "[inav] poll error on init");

		} else if (ret > 0) {
			if (fds_init[0].revents & POLLIN) {
				orb_copy(ORB_ID(sensor_combined), sensor_combined_sub, &sensor);

				if (wait_baro && sensor.baro_timestamp != baro_timestamp) {
					baro_timestamp = sensor.baro_timestamp;

					/* mean calculation over several measurements */
					if (baro_init_cnt < baro_init_num) {
						if (isfinite(sensor.baro_alt_meter)) {
							baro_offset += sensor.baro_alt_meter;
							baro_init_cnt++;
						}

					} else {
						wait_baro = false;
						baro_offset /= (float) baro_init_cnt;
						warnx("baro offs: %.2f", (double)baro_offset);
						mavlink_log_info(mavlink_fd, "[inav] baro offs: %.2f", (double)baro_offset);
						local_pos.z_valid = true;
						local_pos.v_z_valid = true;
					}
				}
			}
		}
	}

	/* main loop */
	struct pollfd fds[1] = {
		{ .fd = vehicle_attitude_sub, .events = POLLIN },
	};

	while (!thread_should_exit) {
		int ret = poll(fds, 1, 20); // wait maximal 20 ms = 50 Hz minimum rate
		hrt_abstime t = hrt_absolute_time();

		if (ret < 0) {
			/* poll error */
			mavlink_log_info(mavlink_fd, "[inav] poll error on init");
			continue;

		} else if (ret > 0) {
			/* act on attitude updates */

			/* vehicle attitude */
			orb_copy(ORB_ID(vehicle_attitude), vehicle_attitude_sub, &att);
			attitude_updates++;

			bool updated;

			/* parameter update */
			orb_check(parameter_update_sub, &updated);

			if (updated) {
				struct parameter_update_s update;
				orb_copy(ORB_ID(parameter_update), parameter_update_sub, &update);
				parameters_update(&pos_inav_param_handles, &params);
			}

			/* actuator */
			orb_check(actuator_sub, &updated);

			if (updated) {
				orb_copy(ORB_ID_VEHICLE_ATTITUDE_CONTROLS, actuator_sub, &actuator);
			}

			/* armed */
			orb_check(armed_sub, &updated);

			if (updated) {
				orb_copy(ORB_ID(actuator_armed), armed_sub, &armed);
			}

			/* sensor combined */
			orb_check(sensor_combined_sub, &updated);

			if (updated) {
				orb_copy(ORB_ID(sensor_combined), sensor_combined_sub, &sensor);

				if (sensor.accelerometer_timestamp != accel_timestamp) {
					if (att.R_valid) {
						/* correct accel bias */
						sensor.accelerometer_m_s2[0] -= acc_bias[0];
						sensor.accelerometer_m_s2[1] -= acc_bias[1];
						sensor.accelerometer_m_s2[2] -= acc_bias[2];

						/* transform acceleration vector from body frame to NED frame */
						for (int i = 0; i < 3; i++) {
							acc[i] = 0.0f;

							for (int j = 0; j < 3; j++) {
								acc[i] += att.R[i][j] * sensor.accelerometer_m_s2[j];
							}
						}

						acc[2] += CONSTANTS_ONE_G;

					} else {
						memset(acc, 0, sizeof(acc));
					}

					accel_timestamp = sensor.accelerometer_timestamp;
					accel_updates++;
				}

				if (sensor.baro_timestamp != baro_timestamp) {
					corr_baro = baro_offset - sensor.baro_alt_meter - z_est[0];
					baro_timestamp = sensor.baro_timestamp;
					baro_updates++;
				}
			}

			/* optical flow */
			orb_check(optical_flow_sub, &updated);

			if (updated) {
				orb_copy(ORB_ID(optical_flow), optical_flow_sub, &flow);

				/* calculate time from previous update */
				float flow_dt = flow_prev > 0 ? (flow.flow_timestamp - flow_prev) * 1e-6f : 0.1f;
				flow_prev = flow.flow_timestamp;

				if ((flow.ground_distance_m > 0.31f) &&
					(flow.ground_distance_m < 4.0f) &&
					(att.R[2][2] > 0.7f) &&
					(fabsf(flow.ground_distance_m - sonar_prev) > FLT_EPSILON)) {

					sonar_time = t;
					sonar_prev = flow.ground_distance_m;
					corr_sonar = flow.ground_distance_m + surface_offset + z_est[0];
					corr_sonar_filtered += (corr_sonar - corr_sonar_filtered) * params.sonar_filt;

					if (fabsf(corr_sonar) > params.sonar_err) {
						/* correction is too large: spike or new ground level? */
						if (fabsf(corr_sonar - corr_sonar_filtered) > params.sonar_err) {
							/* spike detected, ignore */
							corr_sonar = 0.0f;
							sonar_valid = false;

						} else {
							/* new ground level */
							surface_offset -= corr_sonar;
							surface_offset_rate = 0.0f;
							corr_sonar = 0.0f;
							corr_sonar_filtered = 0.0f;
							sonar_valid_time = t;
							sonar_valid = true;
							local_pos.surface_bottom_timestamp = t;
							mavlink_log_info(mavlink_fd, "[inav] new surface level: %.2f", (double)surface_offset);
						}

					} else {
						/* correction is ok, use it */
						sonar_valid_time = t;
						sonar_valid = true;
					}
				}

				float flow_q = flow.quality / 255.0f;
				float dist_bottom = - z_est[0] - surface_offset;

				if (dist_bottom > 0.3f && flow_q > params.flow_q_min && (t < sonar_valid_time + sonar_valid_timeout) && att.R[2][2] > 0.7f) {
					/* distance to surface */
					float flow_dist = dist_bottom / att.R[2][2];
					/* check if flow if too large for accurate measurements */
					/* calculate estimated velocity in body frame */
					float body_v_est[2] = { 0.0f, 0.0f };

					for (int i = 0; i < 2; i++) {
						body_v_est[i] = att.R[0][i] * x_est[1] + att.R[1][i] * y_est[1] + att.R[2][i] * z_est[1];
					}

					/* set this flag if flow should be accurate according to current velocity and attitude rate estimate */
					flow_accurate = fabsf(body_v_est[1] / flow_dist - att.rollspeed) < max_flow &&
							fabsf(body_v_est[0] / flow_dist + att.pitchspeed) < max_flow;

					/* convert raw flow to angular flow (rad/s) */
					float flow_ang[2];
					flow_ang[0] = flow.flow_raw_x * params.flow_k / 1000.0f / flow_dt;
					flow_ang[1] = flow.flow_raw_y * params.flow_k / 1000.0f / flow_dt;
					/* flow measurements vector */
					float flow_m[3];
					flow_m[0] = -flow_ang[0] * flow_dist;
					flow_m[1] = -flow_ang[1] * flow_dist;
					flow_m[2] = z_est[1];
					/* velocity in NED */
					float flow_v[2] = { 0.0f, 0.0f };

					/* project measurements vector to NED basis, skip Z component */
					for (int i = 0; i < 2; i++) {
						for (int j = 0; j < 3; j++) {
							flow_v[i] += att.R[i][j] * flow_m[j];
						}
					}

					/* velocity correction */
					corr_flow[0] = flow_v[0] - x_est[1];
					corr_flow[1] = flow_v[1] - y_est[1];
					/* adjust correction weight */
					float flow_q_weight = (flow_q - params.flow_q_min) / (1.0f - params.flow_q_min);
					w_flow = att.R[2][2] * flow_q_weight / fmaxf(1.0f, flow_dist);

					/* if flow is not accurate, reduce weight for it */
					// TODO make this more fuzzy
					if (!flow_accurate) {
						w_flow *= 0.05f;
					}

					/* under ideal conditions, on 1m distance assume EPH = 10cm */
					eph_flow = 0.1f / w_flow;

					flow_valid = true;

				} else {
					w_flow = 0.0f;
					flow_valid = false;
				}

				flow_updates++;
			}

			/* home position */
			orb_check(home_position_sub, &updated);

			if (updated) {
				orb_copy(ORB_ID(home_position), home_position_sub, &home);

				if (home.timestamp != home_timestamp) {
					home_timestamp = home.timestamp;

					double est_lat, est_lon;
					float est_alt;

					if (ref_inited) {
						/* calculate current estimated position in global frame */
						est_alt = local_pos.ref_alt - local_pos.z;
						map_projection_reproject(&ref, local_pos.x, local_pos.y, &est_lat, &est_lon);
					}

					/* update reference */
					map_projection_init(&ref, home.lat, home.lon);

					/* update baro offset */
					baro_offset += home.alt - local_pos.ref_alt;

					local_pos.ref_lat = home.lat;
					local_pos.ref_lon = home.lon;
					local_pos.ref_alt = home.alt;
					local_pos.ref_timestamp = home.timestamp;

					if (ref_inited) {
						/* reproject position estimate with new reference */
						map_projection_project(&ref, est_lat, est_lon, &x_est[0], &y_est[0]);
						z_est[0] = -(est_alt - local_pos.ref_alt);
					}

					ref_inited = true;
				}
			}

			/* vehicle GPS position */
			orb_check(vehicle_gps_position_sub, &updated);

			if (updated) {
				orb_copy(ORB_ID(vehicle_gps_position), vehicle_gps_position_sub, &gps);

				bool reset_est = false;

				/* hysteresis for GPS quality */
				if (gps_valid) {
					if (gps.eph > max_eph_epv || gps.epv > max_eph_epv || gps.fix_type < 3) {
						gps_valid = false;
						mavlink_log_info(mavlink_fd, "[inav] GPS signal lost");
					}

				} else {
					if (gps.eph < max_eph_epv * 0.7f && gps.epv < max_eph_epv * 0.7f && gps.fix_type >= 3) {
						gps_valid = true;
						reset_est = true;
						mavlink_log_info(mavlink_fd, "[inav] GPS signal found");
					}
				}

				if (gps_valid) {
					double lat = gps.lat * 1e-7;
					double lon = gps.lon * 1e-7;
					float alt = gps.alt * 1e-3;

					/* initialize reference position if needed */
					if (!ref_inited) {
						if (ref_init_start == 0) {
							ref_init_start = t;

						} else if (t > ref_init_start + ref_init_delay) {
							ref_inited = true;

							/* set position estimate to (0, 0, 0), use GPS velocity for XY */
							x_est[0] = 0.0f;
							x_est[1] = gps.vel_n_m_s;
							y_est[0] = 0.0f;
							y_est[1] = gps.vel_e_m_s;

							local_pos.ref_lat = lat;
							local_pos.ref_lon = lon;
							local_pos.ref_alt = alt + z_est[0];
							local_pos.ref_timestamp = t;

							/* initialize projection */
							map_projection_init(&ref, lat, lon);
							warnx("init ref: lat=%.7f, lon=%.7f, alt=%.2f", (double)lat, (double)lon, (double)alt);
							mavlink_log_info(mavlink_fd, "[inav] init ref: %.7f, %.7f, %.2f", (double)lat, (double)lon, (double)alt);
						}
					}

					if (ref_inited) {
						/* project GPS lat lon to plane */
						float gps_proj[2];
						map_projection_project(&ref, lat, lon, &(gps_proj[0]), &(gps_proj[1]));

						/* reset position estimate when GPS becomes good */
						if (reset_est) {
							x_est[0] = gps_proj[0];
							x_est[1] = gps.vel_n_m_s;
							y_est[0] = gps_proj[1];
							y_est[1] = gps.vel_e_m_s;
						}

						/* calculate index of estimated values in buffer */
						int est_i = buf_ptr - 1 - min(EST_BUF_SIZE - 1, max(0, (int)(params.delay_gps * 1000000.0f / PUB_INTERVAL)));
						if (est_i < 0) {
							est_i += EST_BUF_SIZE;
						}

						/* calculate correction for position */
						corr_gps[0][0] = gps_proj[0] - est_buf[est_i][0][0];
						corr_gps[1][0] = gps_proj[1] - est_buf[est_i][1][0];
						corr_gps[2][0] = local_pos.ref_alt - alt - est_buf[est_i][2][0];

						/* calculate correction for velocity */
						if (gps.vel_ned_valid) {
							corr_gps[0][1] = gps.vel_n_m_s - est_buf[est_i][0][1];
							corr_gps[1][1] = gps.vel_e_m_s - est_buf[est_i][1][1];
							corr_gps[2][1] = gps.vel_d_m_s - est_buf[est_i][2][1];

						} else {
							corr_gps[0][1] = 0.0f;
							corr_gps[1][1] = 0.0f;
							corr_gps[2][1] = 0.0f;
						}

						/* save rotation matrix at this moment */
						memcpy(R_gps, R_buf[est_i], sizeof(R_gps));

						w_gps_xy = min_eph_epv / fmaxf(min_eph_epv, gps.eph);
						w_gps_z = min_eph_epv / fmaxf(min_eph_epv, gps.epv);
					}

				} else {
					/* no GPS lock */
					memset(corr_gps, 0, sizeof(corr_gps));
					ref_init_start = 0;
				}

				gps_updates++;
			}
		}

		/* check for timeout on FLOW topic */
		if ((flow_valid || sonar_valid) && t > flow.timestamp + flow_topic_timeout) {
			flow_valid = false;
			sonar_valid = false;
			warnx("FLOW timeout");
			mavlink_log_info(mavlink_fd, "[inav] FLOW timeout");
		}

		/* check for timeout on GPS topic */
		if (gps_valid && t > gps.timestamp_position + gps_topic_timeout) {
			gps_valid = false;
			warnx("GPS timeout");
			mavlink_log_info(mavlink_fd, "[inav] GPS timeout");
		}

		/* check for sonar measurement timeout */
		if (sonar_valid && t > sonar_time + sonar_timeout) {
			corr_sonar = 0.0f;
			sonar_valid = false;
		}

		float dt = t_prev > 0 ? (t - t_prev) / 1000000.0f : 0.0f;
		dt = fmaxf(fminf(0.02, dt), 0.002);		// constrain dt from 2 to 20 ms
		t_prev = t;

		/* increase EPH/EPV on each step */
		if (eph < max_eph_epv) {
			eph *= 1.0f + dt;
		}
		if (epv < max_eph_epv) {
			epv += 0.005f * dt;	// add 1m to EPV each 200s (baro drift)
		}

		/* use GPS if it's valid and reference position initialized */
		bool use_gps_xy = ref_inited && gps_valid && params.w_xy_gps_p > MIN_VALID_W;
		bool use_gps_z = ref_inited && gps_valid && params.w_z_gps_p > MIN_VALID_W;
		/* use flow if it's valid and (accurate or no GPS available) */
		bool use_flow = flow_valid && (flow_accurate || !use_gps_xy);

		bool can_estimate_xy = (eph < max_eph_epv) || use_gps_xy || use_flow;

		bool dist_bottom_valid = (t < sonar_valid_time + sonar_valid_timeout);

		if (dist_bottom_valid) {
			/* surface distance prediction */
			surface_offset += surface_offset_rate * dt;

			/* surface distance correction */
			if (sonar_valid) {
				surface_offset_rate -= corr_sonar * 0.5f * params.w_z_sonar * params.w_z_sonar * dt;
				surface_offset -= corr_sonar * params.w_z_sonar * dt;
			}
		}

		float w_xy_gps_p = params.w_xy_gps_p * w_gps_xy;
		float w_xy_gps_v = params.w_xy_gps_v * w_gps_xy;
		float w_z_gps_p = params.w_z_gps_p * w_gps_z;

		/* reduce GPS weight if optical flow is good */
		if (use_flow && flow_accurate) {
			w_xy_gps_p *= params.w_gps_flow;
			w_xy_gps_v *= params.w_gps_flow;
		}

		/* baro offset correction */
		if (use_gps_z) {
			float offs_corr = corr_gps[2][0] * w_z_gps_p * dt;
			baro_offset += offs_corr;
			corr_baro += offs_corr;
		}

		/* accelerometer bias correction for GPS (use buffered rotation matrix) */
		float accel_bias_corr[3] = { 0.0f, 0.0f, 0.0f };

		if (use_gps_xy) {
			accel_bias_corr[0] -= corr_gps[0][0] * w_xy_gps_p * w_xy_gps_p;
			accel_bias_corr[0] -= corr_gps[0][1] * w_xy_gps_v;
			accel_bias_corr[1] -= corr_gps[1][0] * w_xy_gps_p * w_xy_gps_p;
			accel_bias_corr[1] -= corr_gps[1][1] * w_xy_gps_v;
		}

		if (use_gps_z) {
			accel_bias_corr[2] -= corr_gps[2][0] * w_z_gps_p * w_z_gps_p;
		}

		/* transform error vector from NED frame to body frame */
		for (int i = 0; i < 3; i++) {
			float c = 0.0f;

			for (int j = 0; j < 3; j++) {
				c += R_gps[j][i] * accel_bias_corr[j];
			}

			if (isfinite(c)) {
				acc_bias[i] += c * params.w_acc_bias * dt;
			}
		}

		/* accelerometer bias correction for flow and baro (assume that there is no delay) */
		accel_bias_corr[0] = 0.0f;
		accel_bias_corr[1] = 0.0f;
		accel_bias_corr[2] = 0.0f;

		if (use_flow) {
			accel_bias_corr[0] -= corr_flow[0] * params.w_xy_flow;
			accel_bias_corr[1] -= corr_flow[1] * params.w_xy_flow;
		}

		accel_bias_corr[2] -= corr_baro * params.w_z_baro * params.w_z_baro;

		/* transform error vector from NED frame to body frame */
		for (int i = 0; i < 3; i++) {
			float c = 0.0f;

			for (int j = 0; j < 3; j++) {
				c += att.R[j][i] * accel_bias_corr[j];
			}

			if (isfinite(c)) {
				acc_bias[i] += c * params.w_acc_bias * dt;
			}
		}

		/* inertial filter prediction for altitude */
		inertial_filter_predict(dt, z_est, acc[2]);

		if (!(isfinite(z_est[0]) && isfinite(z_est[1]))) {
			write_debug_log("BAD ESTIMATE AFTER Z PREDICTION", dt, x_est, y_est, z_est, x_est_prev, y_est_prev, z_est_prev, acc, corr_gps, w_xy_gps_p, w_xy_gps_v);
			memcpy(z_est, z_est_prev, sizeof(z_est));
		}

		/* inertial filter correction for altitude */
		inertial_filter_correct(corr_baro, dt, z_est, 0, params.w_z_baro);

		if (use_gps_z) {
			epv = fminf(epv, gps.epv);

			inertial_filter_correct(corr_gps[2][0], dt, z_est, 0, w_z_gps_p);
		}

		if (!(isfinite(z_est[0]) && isfinite(z_est[1]))) {
			write_debug_log("BAD ESTIMATE AFTER Z CORRECTION", dt, x_est, y_est, z_est, x_est_prev, y_est_prev, z_est_prev, acc, corr_gps, w_xy_gps_p, w_xy_gps_v);
			memcpy(z_est, z_est_prev, sizeof(z_est));
			memset(corr_gps, 0, sizeof(corr_gps));
			corr_baro = 0;

		} else {
			memcpy(z_est_prev, z_est, sizeof(z_est));
		}

		if (can_estimate_xy) {
			/* inertial filter prediction for position */
			inertial_filter_predict(dt, x_est, acc[0]);
			inertial_filter_predict(dt, y_est, acc[1]);

			if (!(isfinite(x_est[0]) && isfinite(x_est[1]) && isfinite(y_est[0]) && isfinite(y_est[1]))) {
				write_debug_log("BAD ESTIMATE AFTER PREDICTION", dt, x_est, y_est, z_est, x_est_prev, y_est_prev, z_est_prev, acc, corr_gps, w_xy_gps_p, w_xy_gps_v);
				memcpy(x_est, x_est_prev, sizeof(x_est));
				memcpy(y_est, y_est_prev, sizeof(y_est));
			}

			/* inertial filter correction for position */
			if (use_flow) {
				eph = fminf(eph, eph_flow);

				inertial_filter_correct(corr_flow[0], dt, x_est, 1, params.w_xy_flow * w_flow);
				inertial_filter_correct(corr_flow[1], dt, y_est, 1, params.w_xy_flow * w_flow);
			}

			if (use_gps_xy) {
				eph = fminf(eph, gps.eph);

				inertial_filter_correct(corr_gps[0][0], dt, x_est, 0, w_xy_gps_p);
				inertial_filter_correct(corr_gps[1][0], dt, y_est, 0, w_xy_gps_p);

				if (gps.vel_ned_valid && t < gps.timestamp_velocity + gps_topic_timeout) {
					inertial_filter_correct(corr_gps[0][1], dt, x_est, 1, w_xy_gps_v);
					inertial_filter_correct(corr_gps[1][1], dt, y_est, 1, w_xy_gps_v);
				}
			}

			if (!(isfinite(x_est[0]) && isfinite(x_est[1]) && isfinite(y_est[0]) && isfinite(y_est[1]))) {
				write_debug_log("BAD ESTIMATE AFTER CORRECTION", dt, x_est, y_est, z_est, x_est_prev, y_est_prev, z_est_prev, acc, corr_gps, w_xy_gps_p, w_xy_gps_v);
				memcpy(x_est, x_est_prev, sizeof(x_est));
				memcpy(y_est, y_est_prev, sizeof(y_est));
				memset(corr_gps, 0, sizeof(corr_gps));
				memset(corr_flow, 0, sizeof(corr_flow));

			} else {
				memcpy(x_est_prev, x_est, sizeof(x_est));
				memcpy(y_est_prev, y_est, sizeof(y_est));
			}
		} else {
			/* gradually reset xy velocity estimates */
			inertial_filter_correct(-x_est[1], dt, x_est, 1, params.w_xy_res_v);
			inertial_filter_correct(-y_est[1], dt, y_est, 1, params.w_xy_res_v);
		}

		/* detect land */
		alt_avg += (- z_est[0] - alt_avg) * dt / params.land_t;
		float alt_disp2 = - z_est[0] - alt_avg;
		alt_disp2 = alt_disp2 * alt_disp2;
		float land_disp2 = params.land_disp * params.land_disp;
		/* get actual thrust output */
		float thrust = armed.armed ? actuator.control[3] : 0.0f;

		if (landed) {
			if (alt_disp2 > land_disp2 || thrust > params.land_thr) {
				landed = false;
				landed_time = 0;
			}
			/* reset xy velocity estimates when landed */
			x_est[1] = 0.0f;
			y_est[1] = 0.0f;

		} else {
			if (alt_disp2 < land_disp2 && thrust < params.land_thr) {
				if (landed_time == 0) {
					landed_time = t;    // land detected first time

				} else {
					if (t > landed_time + params.land_t * 1000000.0f) {
						landed = true;
						landed_time = 0;
					}
				}

			} else {
				landed_time = 0;
			}
		}

		if (verbose_mode) {
			/* print updates rate */
			if (t > updates_counter_start + updates_counter_len) {
				float updates_dt = (t - updates_counter_start) * 0.000001f;
				warnx(
					"updates rate: accelerometer = %.1f/s, baro = %.1f/s, gps = %.1f/s, attitude = %.1f/s, flow = %.1f/s",
					(double)(accel_updates / updates_dt),
					(double)(baro_updates / updates_dt),
					(double)(gps_updates / updates_dt),
					(double)(attitude_updates / updates_dt),
					(double)(flow_updates / updates_dt));
				updates_counter_start = t;
				accel_updates = 0;
				baro_updates = 0;
				gps_updates = 0;
				attitude_updates = 0;
				flow_updates = 0;
			}
		}

		if (t > pub_last + PUB_INTERVAL) {
			pub_last = t;

			/* push current estimate to buffer */
			est_buf[buf_ptr][0][0] = x_est[0];
			est_buf[buf_ptr][0][1] = x_est[1];
			est_buf[buf_ptr][1][0] = y_est[0];
			est_buf[buf_ptr][1][1] = y_est[1];
			est_buf[buf_ptr][2][0] = z_est[0];
			est_buf[buf_ptr][2][1] = z_est[1];

			/* push current rotation matrix to buffer */
			memcpy(R_buf[buf_ptr], att.R, sizeof(att.R));

			buf_ptr++;
			if (buf_ptr >= EST_BUF_SIZE) {
				buf_ptr = 0;
			}

			/* publish local position */
			local_pos.xy_valid = can_estimate_xy;
			local_pos.v_xy_valid = can_estimate_xy;
			local_pos.xy_global = local_pos.xy_valid && use_gps_xy;
			local_pos.z_global = local_pos.z_valid && use_gps_z;
			local_pos.x = x_est[0];
			local_pos.vx = x_est[1];
			local_pos.y = y_est[0];
			local_pos.vy = y_est[1];
			local_pos.z = z_est[0];
			local_pos.vz = z_est[1];
			local_pos.landed = landed;
			local_pos.yaw = att.yaw;
			local_pos.dist_bottom_valid = dist_bottom_valid;
			local_pos.eph = eph;
			local_pos.epv = epv;

			if (local_pos.dist_bottom_valid) {
				local_pos.dist_bottom = -z_est[0] - surface_offset;
				local_pos.dist_bottom_rate = -z_est[1] - surface_offset_rate;
			}

			local_pos.timestamp = t;

			orb_publish(ORB_ID(vehicle_local_position), vehicle_local_position_pub, &local_pos);

			if (local_pos.xy_global && local_pos.z_global) {
				/* publish global position */
				global_pos.timestamp = t;
				global_pos.time_gps_usec = gps.time_gps_usec;

				double est_lat, est_lon;
				map_projection_reproject(&ref, local_pos.x, local_pos.y, &est_lat, &est_lon);

				global_pos.lat = est_lat;
				global_pos.lon = est_lon;
				global_pos.alt = local_pos.ref_alt - local_pos.z;

				global_pos.vel_n = local_pos.vx;
				global_pos.vel_e = local_pos.vy;
				global_pos.vel_d = local_pos.vz;

				global_pos.yaw = local_pos.yaw;

				global_pos.eph = eph;
				global_pos.epv = epv;

				if (vehicle_global_position_pub < 0) {
					vehicle_global_position_pub = orb_advertise(ORB_ID(vehicle_global_position), &global_pos);

				} else {
					orb_publish(ORB_ID(vehicle_global_position), vehicle_global_position_pub, &global_pos);
				}
			}
		}
	}

	warnx("stopped");
	mavlink_log_info(mavlink_fd, "[inav] stopped");
	thread_running = false;
	return 0;
}