A licenced aerodrome is required to publish data which includes the actual dimensions of runways and the safe areas around it. At the sides of the runway is a sloped area which must be clear of all obstacles. Nothing that protrudes into it is allowed. At each end of the runway there is also a sloped area that extends and must also be clear of all obstacles. The point at which it is guaranteed to be clear of an obstacle at 50 ft (TODA) is also published. The required slope to avoid an obstacle may have to be moved back shortening the actual runway. So the TORA (take off runway available) may be less than the actual runway dimensions because of this. The aircraft must be capable of lifting off within the TORA and be able to climb above the slope to avoid the published obstacle. Conversely the approaching aircraft must be able to descend above the slope and arrive above the threshold at 50 ft (the screen height): this allows for such things as the undercarriage. It may be necessary to displace the threshold to comply with the slope, shortening the landing runway. From the landing threshold to the end of the runway is the landing distance available (LDA).
The same standards are also part of the aeroplane approval. the take off ground run required and the take off distance (the point at which the aircraft can achieve 50 ft height gain. Obviously these will vary according to the aircraft weight, runway surface, slope, air density and wind velocity. The manual must provide the means to calculate this. The aircraft manual will also give the means to calculate the landing distance which is from 50 ft above the threshold to the point that the pilot can reasonably be able to bring the aircraft to a halt with normal braking. This will need to be factored of course as with the take off.
If you want to study this in detail then the reference is: UK CAA CAP 168 'Licensing of Aerodromes'. For the aircraft performance study the manual.
Last edited by Fl1ingfrog; 19th Feb 2021 at 22:53.