ROS tf 两个常用的函数

/** \brief Get the transform between two frames by frame ID.
   * \param target_frame The frame to which data should be transformed
   * \param source_frame The frame where the data originated
   * \param time The time at which the value of the transform is desired. (0 will get the latest)
   * \param transform The transform reference to fill.  
   *
   * Possible exceptions tf::LookupException, tf::ConnectivityException,
   * tf::MaxDepthException, tf::ExtrapolationException
   */

void lookupTransform(const std::string& target_frame, const std::string& source_frame,
                       const ros::Time& time, StampedTransform& transform) const;

/** \brief Get the transform between two frames by frame ID assuming fixed frame.
   * \param target_frame The frame to which data should be transformed
   * \param target_time The time to which the data should be transformed. (0 will get the latest)
   * \param source_frame The frame where the data originated
   * \param source_time The time at which the source_frame should be evaluated. (0 will get the latest)
   * \param fixed_frame The frame in which to assume the transform is constant in time.
   * \param transform The transform reference to fill.  
   *
   * Possible exceptions tf::LookupException, tf::ConnectivityException,
   * tf::MaxDepthException, tf::ExtrapolationException
   */

void lookupTransform(const std::string& target_frame, const ros::Time& target_time,
                       const std::string& source_frame, const ros::Time& source_time,
                       const std::string& fixed_frame, StampedTransform& transform) const;