Here's the problem:

At any specific altitude, how far away from the centre of your aircraft, if the land/ ground feature you can see immediately off the wingtip?

My question is inspired by a quote from Johnnie Johnsons's book "ing leader" where he talks about the huge land distances which were obscured yb the Spitfire's wings at altitude. I ahve also noticed online that many people tend to reference their location by what they can see off their wing tip, or behind their trailing edge. Often, it seems to me, people massively under-estimate how far away those land features actually are from their current position.

So, the problem is relatively basic trig.

In level flight (assuming alos level attitude) by drawing a triangle from the pilot's eye posiiton to the wingtip we have a hypotenuse (c) and and angle "B" relative to the aircraft's z-axis.

The distance from the Pilot's eyes down the a-axis to the Wing Datum line gives us out "a" side of the triangle.

The distance along "b" is simple half of the aircraft's wingspan.

See image:

We can then simply extend the z-axis line down the full altitude of the aircraft to get the totla length for the "ground positon" "a" side of th etriangle. Then using trig we can work out how far away down the hypotenute (c) the landmarks are, at any given altitude.

I already know the following:

side b = half of 11.23m (11230mm) = 5615 mm

Sides c and a I cannot know until I can work out what the distance is (typically) between the pilot's eye level in the cockpit and the wing datum.

I have this document which has some measurements:

https://i.imgur.com/gtmjNU4.png

I think length "L" is a start, but I need to project tha up tot he eyeline of a pilot... say 15cm below the canopy roof . . .

Does anyone have access to a diagram or a best-guess of the distance between a pilot's eye level and the "wing datum" of a spit IX?