map_origin_broadcaster

Maintains the origin of the map frame and statically broadcasts that origin. The program aims to achieve global consistency of the map in the GPS frame and was tested using slam_gmapping.

Caveats

This node simply listens to TF transformations between gps_origin and gps_base_link. This means that there needs to be a node that broadcasts the transformations between the GPS origin and the GPS mobile base (for example, gnss_broadcaster). Additionally, the GPS mobile base location needs to be accurate (e.g. RTK fix, FloatRTK fix etc.) because only one coordinate location is taken (without taking the average of N samples etc.).

Once it receives a transformation, it publishes that as a static transformation between gps_origin and map. On doing so, the difference between odom and base_link (i.e. the potentially-inaccurate-but-the-only-best-guess distance traveled since the odometry node was brought up) is subtracted because the map is set to the origin of the odom frame upon creation, meaning that the "map origin" is equal to the current odom origin.

Parameters

In the parentheses are the default values for each parameter.

• gps_origin_frame (gps_origin): The frame attached to the GPS origin.
• gps_base_frame (gps_base_link): The frame attached to the base frame, calculated using GNSS instruments.
• map_frame (map): The frame attached to the map.
• odom_frame (odom): The frame attached to the odometry system.
• base_frame (base_link): The frame attached to the mobile base.
• save_on_exit (true): Whether to save the location of the map origin to a file on exiting.

Saved file

When the save_on_exit parameter is set to true, the program saves the location of the map origin on exit. The file is a CSV file with the file name being the date and time when the coordinate information received. The file contains the following information in the respective order:

1. Date and time when the coordinate information was received
2. Frame name of the GPS origin
3. Frame name of the map origin
4. Translation in the X direction
5. Translation in the Y direction
6. Translation in the Z direction
7. Rotation quaternion X
8. Rotation quaternion Y
9. Rotation quaternion Z
10. Rotation quaternion W

When the node is launched using the launch file, the file is saved in ~/.ros. When invoked with rosrun, it should save the file to the current directory (i.e. wherever the rosrun was invoked).

License

MIT

Author

Naoki Mizuno (mizuno.naoki@rm.is.tohoku.ac.jp)