What does FW_LND_HVIRT do?

Experimenting with landings today, and I can’t figure out what this parameter does

It’s for calculating the flare. See this diagram https://github.com/PX4/Firmware/blob/master/Documentation/fw_landing.png
Used here - https://github.com/PX4/Firmware/blob/master/src/modules/fw_pos_control_l1/landingslope.cpp#L81

We could definitely do a better job with documentation here.

Interesting. I just tested it out in the field and figured out that smaller values appear to move the glideslope back from the land waypoint.

And what does it means?