T4, I was also waiting for that but after I re-read the posts I think he was trying to give a response with this:
It must obviously must include sightof some, or all of the helideck lights. Otherwise you cannot make a plan to manouvre into position to land. If Ovality is lacking, due to obstructions and such like, then sufficient texture and references, coming off the surrounding structure, when combined with visual parts of the helideck, provide sufficient references to enable the Final Descent to be made by sole visual reference alone.
I am working on a better description for the updated version of the profiles but I rather suspect it needs some kind of expertise, both in language and the technical side, to tidy it up into something that is watertight (if that is possible).
Of course the very fact that we hopefully are 200 feet above the deck at this point should give us a far better chance of assimilating and interpreting the avialable references.
Regards
Aser