Real time rtk gps altitude reading sent to AlceOSD for balcony shots?

hey I was wondering if i can read the altitude data from a rtk gps unit send it through my alceosd then to a monitor so we can read the altitude of the drone in real time??
I have had read through the manuals but i cant find what im after.
More specifically, I want to be able to very accurately record my height above the ground while having the camera looking out at a straight and level view from the bottom of the helicopter.
In short, I record “balcony” shots and I need to be able to accurately measure the height of the subject(s) I am viewing without using waypoints.