gps_conversion.cpp

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/*

 Copyright (c) 2012, Markus Achtelik, ASL, ETH Zurich, Switzerland
 You can contact the author at <markus dot achtelik at mavt dot ethz dot ch>

 All rights reserved.

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 * Redistributions of source code must retain the above copyright
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 * Redistributions in binary form must reproduce the above copyright
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 documentation and/or other materials provided with the distribution.
 * Neither the name of ETHZ-ASL 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
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 WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 DISCLAIMED. IN NO EVENT SHALL ETHZ-ASL BE LIABLE FOR ANY
 DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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 */

#include "gps_conversion.h"

namespace asctec_hl_gps
{

GpsConversion::GpsConversion() :
  nh_(""), gps_sub_sync_(nh_, "fcu/gps", 1), imu_sub_sync_(nh_, "fcu/imu_custom", 1),
      gps_imu_sync_(GpsImuSyncPolicy(10), gps_sub_sync_, imu_sub_sync_), have_reference_(false),
      height_offset_(0), set_height_zero_(false), Q_90_DEG(sqrt(2.0) / 2.0, 0, 0, sqrt(2.0) / 2.0)
{
  ros::NodeHandle nh;
  ros::NodeHandle pnh("~");

  imu_sub_ = nh.subscribe("fcu/imu_custom", 1, &GpsConversion::imuCallback, this);
  gps_sub_ = nh.subscribe("fcu/gps", 1, &GpsConversion::gpsCallback, this);
  gps_custom_sub_ = nh.subscribe("fcu/gps_custom", 1, &GpsConversion::gpsCustomCallback, this);

  gps_pose_pub_ = nh_.advertise<geometry_msgs::PoseWithCovarianceStamped> ("fcu/gps_pose", 1);
  gps_position_pub_ = nh_.advertise<asctec_hl_comm::PositionWithCovarianceStamped> ("fcu/gps_position", 1);
  gps_custom_pub_ = nh_.advertise<asctec_hl_comm::GpsCustomCartesian> ("fcu/gps_position_custom", 1);
  zero_height_srv_ = nh.advertiseService("set_height_zero", &GpsConversion::zeroHeightCb, this);

  pnh.param("use_pressure_height", use_pressure_height_, false);
  ROS_INFO_STREAM("using height measurement from "<< (use_pressure_height_?"pressure sensor":"GPS"));

  if (use_pressure_height_)
  {
    gps_imu_sync_.registerCallback(boost::bind(&GpsConversion::syncCallback, this, _1, _2));
    gps_imu_sync_.setInterMessageLowerBound(0, ros::Duration(0.180)); // gps arrives at max with 5 Hz
  }

  if (nh.getParam("/gps_ref_latitude", ref_latitude_))
  {
    if (nh.getParam("/gps_ref_longitude", ref_longitude_))
    {
      if (nh.getParam("/gps_ref_altitude", ref_altitude_))
      {
        initReference(ref_latitude_, ref_longitude_, ref_altitude_);
        have_reference_ = true;
      }
    }
  }
}

bool GpsConversion::zeroHeightCb(std_srvs::EmptyRequest & req, std_srvs::EmptyResponse & resp)
{
  set_height_zero_ = true;
  return true;
}

void GpsConversion::syncCallback(const sensor_msgs::NavSatFixConstPtr & gps,
                                 const asctec_hl_comm::mav_imuConstPtr & imu)
{
  if (gps->status.status != sensor_msgs::NavSatStatus::STATUS_FIX)
  {
    ROS_WARN_STREAM_THROTTLE(1, "No GPS fix");
    return;
  }

  if (!have_reference_)
  {
    ROS_WARN_STREAM_THROTTLE(1, "No GPS reference point set, not publishing");
    return;
  }

  if (set_height_zero_)
  {
    set_height_zero_ = false;
    height_offset_ = imu->height;
  }

  if (use_pressure_height_)
  {
    asctec_hl_comm::PositionWithCovarianceStampedPtr msg(new asctec_hl_comm::PositionWithCovarianceStamped);
    msg->header = gps->header;
    msg->position = wgs84ToEnu(gps->latitude, gps->longitude, gps->altitude);
    msg->position.z = imu->height - height_offset_;

    gps_position_pub_.publish(msg);
  }
}

void GpsConversion::gpsCallback(const sensor_msgs::NavSatFixConstPtr & gps)
{
  if (!have_reference_)
  {
    ROS_WARN_STREAM_THROTTLE(1, "No GPS reference point set, not publishing");
    return;
  }

  if (gps->status.status == sensor_msgs::NavSatStatus::STATUS_FIX)
  {
    gps_position_ = wgs84ToEnu(gps->latitude, gps->longitude, gps->altitude);
    if (!use_pressure_height_)
    {
      asctec_hl_comm::PositionWithCovarianceStampedPtr msg(new asctec_hl_comm::PositionWithCovarianceStamped);
      msg->header = gps->header;
      msg->position = gps_position_;
      msg->covariance = gps->position_covariance;
      gps_position_pub_.publish(msg);
    }
  }
  else
  {
    gps_position_.x = gps_position_.y = gps_position_.z = 0;
  }
}

void GpsConversion::gpsCustomCallback(const asctec_hl_comm::GpsCustomConstPtr & gps)
{
  if (!have_reference_)
  {
    ROS_WARN_STREAM_THROTTLE(1, "No GPS reference point set, not publishing");
    return;
  }

  if (gps->status.status == sensor_msgs::NavSatStatus::STATUS_FIX)
  {
    geometry_msgs::Point pos = wgs84ToEnu(gps->latitude, gps->longitude, gps->altitude);

    asctec_hl_comm::GpsCustomCartesianPtr msg(new asctec_hl_comm::GpsCustomCartesian);
    msg->header = gps->header;
    msg->position = pos;
    msg->position_covariance = gps->position_covariance;

    // rotate velocity to ENU !
    msg->velocity_x = gps->velocity_x;
    msg->velocity_y = gps->velocity_y;

    msg->velocity_covariance = gps->velocity_covariance;

    if (use_pressure_height_)
    {
      msg->position.z = gps->pressure_height - height_offset_;
    }
    gps_custom_pub_.publish(msg);
  }

}

void GpsConversion::imuCallback(const asctec_hl_comm::mav_imuConstPtr & imu)
{
  if (gps_position_.x == 0 && gps_position_.y == 0 && gps_position_.z == 0)
  {
    ROS_WARN_STREAM_THROTTLE(1, "No GPS fix");
    return;
  }

  if (!have_reference_)
  {
    ROS_WARN_STREAM_THROTTLE(1, "No GPS reference point set, not publishing");
    return;
  }

  if (set_height_zero_)
  {
    set_height_zero_ = false;
    height_offset_ = imu->height;
  }

  if (gps_pose_pub_.getNumSubscribers() > 0)
  {
    geometry_msgs::PoseWithCovarianceStampedPtr msg(new geometry_msgs::PoseWithCovarianceStamped);

    // magnetic compass is zero when pointing north, need to rotate measurement 90 deg towards east to be consistent with ENU

    Eigen::Quaterniond orientation(imu->orientation.w, imu->orientation.x, imu->orientation.y, imu->orientation.z);
    orientation = Q_90_DEG * orientation;
    msg->header = imu->header;
    msg->pose.pose.orientation.w = orientation.w();
    msg->pose.pose.orientation.x = orientation.x();
    msg->pose.pose.orientation.y = orientation.y();
    msg->pose.pose.orientation.z = orientation.z();
    msg->pose.pose.position = gps_position_;
    msg->pose.pose.position.z = imu->height - height_offset_;

    gps_pose_pub_.publish(msg);
  }
}

void GpsConversion::initReference(const double & latitude, const double & longitude, const double & altitude)
{
  Eigen::Matrix3d R;
  double s_long, s_lat, c_long, c_lat;
  sincos(latitude * DEG2RAD, &s_lat, &c_lat);
  sincos(longitude * DEG2RAD, &s_long, &c_long);

  R(0, 0) = -s_long;
  R(0, 1) = c_long;
  R(0, 2) = 0;

  R(1, 0) = -s_lat * c_long;
  R(1, 1) = -s_lat * s_long;
  R(1, 2) = c_lat;

  R(2, 0) = c_lat * c_long;
  R(2, 1) = c_lat * s_long;
  R(2, 2) = s_lat;

  ecef_ref_orientation_ = Eigen::Quaterniond(R);

  ecef_ref_point_ = wgs84ToEcef(latitude, longitude, altitude);
}

Eigen::Vector3d GpsConversion::wgs84ToEcef(const double & latitude, const double & longitude, const double & altitude)
{
  const double a = 6378137.0; // semi-major axis
  const double e_sq = 6.69437999014e-3; // first eccentricity squared

  double s_long, s_lat, c_long, c_lat;
  sincos(latitude * DEG2RAD, &s_lat, &c_lat);
  sincos(longitude * DEG2RAD, &s_long, &c_long);

  const double N = a / sqrt(1 - e_sq * s_lat * s_lat);

  Eigen::Vector3d ecef;

  ecef[0] = (N + altitude) * c_lat * c_long;
  ecef[1] = (N + altitude) * c_lat * s_long;
  ecef[2] = (N * (1 - e_sq) + altitude) * s_lat;

  return ecef;
}

Eigen::Vector3d GpsConversion::ecefToEnu(const Eigen::Vector3d & ecef)
{
  return ecef_ref_orientation_ * (ecef - ecef_ref_point_);
}

geometry_msgs::Point GpsConversion::wgs84ToEnu(const double & latitude, const double & longitude,
                                               const double & altitude)
{
  geometry_msgs::Point ret;
  Eigen::Vector3d tmp;
  tmp = ecefToEnu(wgs84ToEcef(latitude, longitude, altitude));
  ret.x = tmp[0];
  ret.y = tmp[1];
  ret.z = tmp[2];

  // debug ...
  //  double dbg_x, dbg_y;
  //  latlon2xy_dbg(ref_latitude_, ref_longitude_, latitude, longitude, &dbg_x, &dbg_y);
  //  ROS_INFO("local metric coordinates: x: %f/%f y: %f/%f", ret.x, dbg_x, ret.y, dbg_y);

  return ret;
}

geometry_msgs::Point GpsConversion::wgs84ToNwu(const double & latitude, const double & longitude,
                                               const double & altitude)
{
  geometry_msgs::Point ret;
  Eigen::Vector3d tmp;
  tmp = ecefToEnu(wgs84ToEcef(latitude, longitude, altitude));
  ret.x = tmp[1];
  ret.y = -tmp[0];
  ret.z = tmp[2];

  // debug ...
  //  double dbg_x, dbg_y;
  //  latlon2xy_dbg(ref_latitude_, ref_longitude_, latitude, longitude, &dbg_x, &dbg_y);
  //  ROS_INFO("local metric coordinates: x: %f/%f y: %f/%f", ret.x, dbg_y, ret.y, -dbg_x);

  return ret;
}

} // end namespace