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/**
* @file gnss.cpp
*
* @author Pavel Kirienko <pavel.kirienko@gmail.com>
* @author Andrew Chambers <achamber@gmail.com>
*
*/
#include "gnss.hpp"
#include <systemlib/err.h>
#include <mathlib/mathlib.h>
#define MM_PER_CM 10 // Millimeters per centimeter
UavcanGnssBridge::UavcanGnssBridge(uavcan::INode &node) :
_node(node),
_uavcan_sub_status(node),
_report_pub(-1)
{
}
const char *UavcanGnssBridge::get_name() const { return "gnss"; }
int UavcanGnssBridge::init()
{
int res = -1;
// GNSS fix subscription
res = _uavcan_sub_status.start(FixCbBinder(this, &UavcanGnssBridge::gnss_fix_sub_cb));
if (res < 0)
{
warnx("GNSS fix sub failed %i", res);
return res;
}
// Clear the uORB GPS report
memset(&_report, 0, sizeof(_report));
warnx("gnss sensor bridge init ok");
return res;
}
void UavcanGnssBridge::gnss_fix_sub_cb(const uavcan::ReceivedDataStructure<uavcan::equipment::gnss::Fix> &msg)
{
_report.timestamp_position = hrt_absolute_time();
_report.lat = msg.lat_1e7;
_report.lon = msg.lon_1e7;
_report.alt = msg.alt_1e2 * MM_PER_CM; // Convert from centimeter (1e2) to millimeters (1e3)
_report.timestamp_variance = _report.timestamp_position;
// Check if the msg contains valid covariance information
const bool valid_position_covariance = !msg.position_covariance.empty();
const bool valid_velocity_covariance = !msg.velocity_covariance.empty();
if (valid_position_covariance) {
float pos_cov[9];
msg.position_covariance.unpackSquareMatrix(pos_cov);
// Horizontal position uncertainty
const float horizontal_pos_variance = math::max(pos_cov[0], pos_cov[4]);
_report.eph = (horizontal_pos_variance > 0) ? sqrtf(horizontal_pos_variance) : -1.0F;
// Vertical position uncertainty
_report.epv = (pos_cov[8] > 0) ? sqrtf(pos_cov[8]) : -1.0F;
} else {
_report.eph = -1.0F;
_report.epv = -1.0F;
}
if (valid_velocity_covariance) {
float vel_cov[9];
msg.velocity_covariance.unpackSquareMatrix(vel_cov);
_report.s_variance_m_s = math::max(math::max(vel_cov[0], vel_cov[4]), vel_cov[8]);
/* There is a nonlinear relationship between the velocity vector and the heading.
* Use Jacobian to transform velocity covariance to heading covariance
*
* Nonlinear equation:
* heading = atan2(vel_e_m_s, vel_n_m_s)
* For math, see http://en.wikipedia.org/wiki/Atan2#Derivative
*
* To calculate the variance of heading from the variance of velocity,
* cov(heading) = J(velocity)*cov(velocity)*J(velocity)^T
*/
float vel_n = msg.ned_velocity[0];
float vel_e = msg.ned_velocity[1];
float vel_n_sq = vel_n * vel_n;
float vel_e_sq = vel_e * vel_e;
_report.c_variance_rad =
(vel_e_sq * vel_cov[0] +
-2 * vel_n * vel_e * vel_cov[1] + // Covariance matrix is symmetric
vel_n_sq* vel_cov[4]) / ((vel_n_sq + vel_e_sq) * (vel_n_sq + vel_e_sq));
} else {
_report.s_variance_m_s = -1.0F;
_report.c_variance_rad = -1.0F;
}
_report.fix_type = msg.status;
_report.timestamp_velocity = _report.timestamp_position;
_report.vel_n_m_s = msg.ned_velocity[0];
_report.vel_e_m_s = msg.ned_velocity[1];
_report.vel_d_m_s = msg.ned_velocity[2];
_report.vel_m_s = sqrtf(_report.vel_n_m_s * _report.vel_n_m_s + _report.vel_e_m_s * _report.vel_e_m_s + _report.vel_d_m_s * _report.vel_d_m_s);
_report.cog_rad = atan2f(_report.vel_e_m_s, _report.vel_n_m_s);
_report.vel_ned_valid = true;
_report.timestamp_time = _report.timestamp_position;
_report.time_gps_usec = uavcan::UtcTime(msg.gnss_timestamp).toUSec(); // Convert to microseconds
_report.satellites_used = msg.sats_used;
if (_report_pub > 0) {
orb_publish(ORB_ID(vehicle_gps_position), _report_pub, &_report);
} else {
_report_pub = orb_advertise(ORB_ID(vehicle_gps_position), &_report);
}
}