I’m a bit confused about screen height definition and I’m seeking help to understand it. I understand that this height for landings is at least 50 ft above the landing threshold for all airplane categories. For takeoff is at least 50 ft or more for Normal and Utility categories and at least 35 ft or more for the Transport category. My question is: For takeoffs is this screen height measured above the departure end of the runway (or above the end of the clearway if any) or it’s measured when a Piper for example is 50 ft above the runway after taking off?
If it’s measured above the DER, does that mean that the actual takeoff DISTANCE of a runway with no clearway will be the entire runway length always? Since the definition of Takeoff Distance is the distance from the Brake Release Point to when the plane crosses the screen height?