Measured ski jump distance

Here is the answer to my question from last year: which measurement is displayed as jumped distance?
It's a bit more complicated than just putting measurement tape on the ground. Following is my interpretation of the answers I got from people in "the jumping businesses".

First 60m marking on the ground is determined with straight 60m line from the middle of the edge where jumper takes off to the side of the landing area on the ground - line B on the drawing below. The width of landing area is predetermined from geometrical standards for jumping hills and linearly increases with distance from ramp. First ground marking is where the slope of the landing area gets straight (from side view). And it is less than 60m on smaller jumping hills.
From first ground marking onward the distance is measured and added to initial 60m from projected length on the side of the landing area. This means that for each unit that jumper flies over straight beneath him on the ground a bit more is added to his result because measurement tape on the side of the landing area is put at a slight angle - line A.
Final distance is B + A. I must note that proportions on my drawings are way off. Whole jumping hill is much much longer and angles are so small that measured distances are almost not skewed (from what? :) ).

Thanks to T. Verdnik and M. Tepes for the insights!