Add custom GZ -> ROS mapping (Humble/Garden)

[AntonioViscomi]

Hi all,
I need to use Gazebo Garden alongside ROS 2 Humble . I want to use the ros_gz_bridge to obtain measurements from virtual sensors on my robot and process them in ROS.

In my ros_gz version (this one ) there is no mapping between gz.msgs.NavSat and gps_msgs/msg/GPSFix.

I need this mapping because I want to transport also the ENU velocity in ROS, which is not possible using sensor_msgs/msg/NavSatFix

Desired behavior

A map betweem gz.msgs.NavSat and gps_msgs/msg/GPSFix in ros_gz_bridge (ros-humble-ros-gzgarden).

Alternatives considered

I've cloned the "humble" branch (which should correspond to my installed version of ros_gz_bridge) and:

1. I've included gps_msgs.hpp in ros_gz/ ros_gz_bridge/include/ros_gz_bridge/convert
2. Added #include <ros_gz_bridge/convert/gps_msgs.hpp> to convert.hpp
3. Added gps_msgs.cpp in ros_gz/ros_gz_bridge/src/convert
4. Added inside ros_gz/ros_gz_bridge/mappings.py:

  'gps_msgs': [
        Mapping('GPSFix', 'NavSat'),
    ], 

5. Added gps_msgs in package.xml

I am unsure if this will work because I've installed gps_msgs as a custom interface inside my custom interfaces package and I also need to ffigure out how to install this "new package" I've created. Am I missing anything?

Additional context:

OS: Ubuntu 22.04.

[ahcorde]

I created backports for Iron and Humble

• [backport Humble] Create bridge for GPSFix msg (#316) #538
• [backport Iron] Create bridge for GPSFix msg (#316) #537

[AntonioViscomi]

Thanks a lot.
I've been able to solve this issue by myself, sharing the solution could be useful?

[yschulz]

I would be more than happy to open another issue for this, but I think this fits here and since this issue is still open:

I am actually very interested in custom message mappings. With the ease of protobuf message generation, both in ros and in gazebo, it feels necessary that I should be able to generate my own custom mappings by configuration instead of programmatically. Even programmatically it seems necessary to fork this repo and inject the mappings directly like @AntonioViscomi has suggested in his first comment. Is there any intent of adding a plugin like api or cmake generations or a cli tool to make this process easier?

[azeey]

Is there any intent of adding a plugin like api or cmake generations or a cli tool to make this process easier?

Yes, we would like to add this at some point, but I don't think there's an actual issue for it. I know for sure we've had discussions about it. The code was adapted from https://github.com/ros2/ros1_bridge/ which I've been told has a way to add custom messages, but I haven't tried it myself. If anyone would be willing to figure out how it's done for ros1_bridge and adapt it to ros_gz_bridge, it would be fantastic!

[yschulz]

Thanks for the quick reply and the link, I can see the resemblance.

I would gladly take a look into it and see how this can be integrated here in the gz bridge. When I have a better overview I'd open a new issue!