Does this only work with ceiling mounted markers?

[anfederman]

Even in simulation, it appears that markers have to be located on the ceiling.

Even If I set the camera to look at wall mounted markers, it show their location above the robot.

This is on a magni_silver using the camera_extrinsics forward mounting, which inverts the camera. using vFlip doen't help.

[ivan140]

You should check the topic /fiducial_transforms and see whether the coordinates there in respect to the camera make sense. If so, check where the x axis of the camera frame is headed: it should look in the same direction as your camera.
We use the package for floor based markers with the small modification that z distance is always constant (since robot is driving on floor).