Stack Exchange network consists of 175 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.
Is a 3-degree glideslope based from the runway surface slope at the point where the antenna is installed or is it referenced to a zero-degree plane?
If you know of a design document or FAR/AIM reference, please include that as well.
It is referenced to the zero-degree plane, and depending on obstacle clearance it may be a little steeper (3.5° or 4°). There is no reason to refer it to the runway slope as it defines a sink rate to speed ratio during final approach.
Required, but never shown