ROS 2 Topics (Carter Warehouse)¶
ROS 2 topics published by the carter_warehouse_apriltags_worker.usd scene in Isaac Sim, plus topics added by the Isaac ROS container.
Active sensors
The Nova Carter has many sensors but only the front stereo camera, front 3D lidar, and chassis IMU are publishing active data topics in this scene. The remaining sensor frames exist in the TF tree but don't have corresponding data topics.
Sensors¶
| Topic | Type | Description |
|---|---|---|
/front_stereo_camera/left/image_rect_color |
sensor_msgs/Image |
Left stereo camera (rectified) |
/front_stereo_camera/right/image_rect_color |
sensor_msgs/Image |
Right stereo camera (rectified) |
/front_stereo_camera/left/camera_info |
sensor_msgs/CameraInfo |
Left camera calibration |
/front_stereo_camera/right/camera_info |
sensor_msgs/CameraInfo |
Right camera calibration |
/front_3d_lidar/lidar_points |
sensor_msgs/PointCloud2 |
3D lidar point cloud |
/chassis/imu |
sensor_msgs/Imu |
Chassis IMU |
/front_stereo_imu/imu |
sensor_msgs/Imu |
Front stereo camera IMU |
/back_stereo_imu/imu |
sensor_msgs/Imu |
Back stereo camera IMU |
/left_stereo_imu/imu |
sensor_msgs/Imu |
Left stereo camera IMU |
/right_stereo_imu/imu |
sensor_msgs/Imu |
Right stereo camera IMU |
Rectified images
"Rectified" means lens distortion is removed and stereo pairs are aligned so left/right pixels share the same row -- ready for depth computation. In simulation this is a formality (virtual cameras have no distortion), but the topic names match real Nova Carter camera pipelines.
Robot State¶
| Topic | Type | Description |
|---|---|---|
/chassis/odom |
nav_msgs/Odometry |
Robot position and velocity (ground truth from sim) |
/tf |
tf2_msgs/TFMessage |
Transform tree -- spatial relationships between all frames |
/clock |
rosgraph_msgs/Clock |
Simulation time |
Odometry is ground truth
In simulation, /chassis/odom is perfect -- no drift, no noise. On a real robot, odometry accumulates error over time. This is why SLAM (like cuVSLAM) exists: to correct drift using visual landmarks.
Control¶
| Topic | Type | Description |
|---|---|---|
/cmd_vel |
geometry_msgs/Twist |
Velocity commands (linear.x = forward/back, angular.z = turn) |
Added by Container¶
These topics are created by nodes in the Isaac ROS container, not by Isaac Sim itself.
| Topic | Type | Description |
|---|---|---|
/front_stereo_camera/left/compressed_video |
foxglove_msgs/CompressedVideo |
H.264 NVENC compressed stream (from republisher) |
/joy |
sensor_msgs/Joy |
Joystick input (from Foxglove joystick extension) |
Unused Topics¶
The image_transport republisher auto-advertises these topics but nothing publishes to them:
/out, /out/compressed, /out/compressedDepth, /out/theora, /out/zstd
These are harmless artifacts of the image_transport plugin system.
TF Tree¶
The Nova Carter robot has a large sensor suite. The transform tree shows how every frame relates to base_link:
odom <- world-fixed reference frame
+-- base_link <- robot center (ground plane)
|-- nova_carter <- robot body
| |-- wheel_left
| |-- wheel_right
| +-- caster_frame_base
| |-- caster_swivel_left -> caster_wheel_left
| +-- caster_swivel_right -> caster_wheel_right
|-- chassis_imu
|-- front_3d_lidar
|-- front/back_2d_lidar
|-- front_stereo_camera (left_optical, right_optical, imu)
|-- left_stereo_camera (left_optical, right_optical, imu)
|-- right_stereo_camera (left_optical, right_optical, imu)
|-- rear_stereo_camera (left_optical, right_optical, imu)
|-- front/left/right/back_fisheye_camera_optical
|-- front/left/right/back_hawk (stereo pairs)
+-- mount
Each transform is a 4x4 homogeneous matrix (rotation + translation). ROS uses the TF tree to convert points between frames -- e.g., transforming a lidar point from the front_3d_lidar frame to odom (world coordinates).