Re: [Flightgear-devel] Further FGRunway work

[Martin S. <Mar...@mg...>]

James,
I can't tell much about the use cases in the FlightGear code, just from
real-life experience. Take this as an aide, if it helps you - if it
doesn't help, I dont mind you ignoring it silently  :-)

James Turner wrote:

> One interesting thing I've come across is how the runway _length and  
> _width fields are used - it turns out they're pretty much always used  
> to calculate some particular positions on the runway, notably the  
> threshold and the 'other end' point (sorry, there must be a better  
> piece of terminology than that), or some offset from those points - eg  
> five metres in, or several NM 'out' along the extended runway  
> centreline.

Personally I'd simply call this 'other end' the 'opposite threshold' -
but I'm not a native English speaker, so there might be a different,
'official' definition for it.
When you look at the 'data/Scenery/Airports/K/H/A/KHAF.threshold.xml'
file for example, then you'll realize that the notation almost matches
the use case you're describing here: Threshold position plus the
heading along the centerline.

In real-life, the displaced threshold doesn't count for takeoff -
you're going to begin your start run wherever you enter the runway,
shortly behind the 'reglar' threshold. I guess, this should (logically)
also apply for the cases when a certain threshold offset is being
calculated in FlightGear for takeoff.
The stopway is a different thing. It lies outside the area that's being
embraced by the two regular thresholds, you don't use it for takeff,
you should not use it for landing - but it might serve as your life
insurance if you're too-high-to-fast during aproach ....

Cheers,
	Martin.
-- 
 Unix _IS_ user friendly - it's just selective about who its friends are !
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