This `/trajectory_query` service allows to look up trajectory segments
from the pose graph.
This can be useful if one wants to get optimized trajectory data from
the current SLAM run and listening to live TF data would be too noisy.
For example, to stitch buffered point cloud data from a depth sensor
based on a recent localization trajectory segment of a robot.
Before, the pose graph trajectory nodes were not available except for
the trajectory marker topic (only positions, no orientation; inefficient)
or after serialization (which is not practical in live operation).
Michael Grupp