Custom 3D Positioning System

i’m trying to understand how can i use a 3D positioning device ( such that i will know the local position without EKF estimator ).At the moment, this device is connected to a companion computer ( Rpi4 ) running Ros2, so i can create a node that sample this device and publish the x,y,z local position. My problem is that i don’t know which topic i need to use in order to send this position to a piwhawk4 controller, such that the position controller on the Pixhawk4 use the sampled 3D position as current position and not local position provided by estimator.
Any help?