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P3D v4 Runway position

J

jeehell

Messages
43
Country
france
Hi,

It's not per se an issue with ADE, but rather a plea for some precision on inner workings of ADE.

I am doing some developments on external runway lighting. I use data I extract from stock airport in ADE (basically, I open a stock airport in ADE, click the runway, select the XML view and copy/paste data to my addon config file).
I have quite accurate positioning, however, using the true heading declared in BGL file, it seems to be off by a few tenths of degrees, so over the length of runway, it can be visible.

What I actually do is take the RWY LAT/LON/HDG from the XML view.
I use a WGS84 lib (ADACALC from Hervé Sors, I confirm it is WGS84 and NOT spherical model/Great Circle) to find the runway beginning (so HDG + 180) and start building my lights from there.
When I compare the new LAT/LON I find and the ones I "measure" in ADE (mouse pointer over the same spot), I have some notable difference (OK here I am talking anyway in 50cm magnitude...).

I do not know where the error appears exactly. What lib does ADE use?
Is there some rounding performed in FSX/P3D on the HDG?

A picture is worth thousands words. On the left, lights are almost outside the RWY rectangle. On the right, they are inside the white markings:
lights.jpg


Thanks
Jean Luc
 
Hi

This is really driving me nuts.

rhetorical question: What HDG is actually in the BGL file? I understand it is a TRUE HEADING alright, so real questions:
1. is it the initial heading on the geodesic curve from RWY beginning to RWY end?
2. is it the initial heading on the geodesic curve from RWY middle point to the runway end?
3. is it the final heading on the geodesic curve from runway start to RWY middle point ?
4. is it an average heading? if so averaged how?
5. is it a rhumbline heading? if so what is the reference point?
6. else??

I have tried answers 1 thru 3 and no luck.
In a few airports I tried (south east France, near 45N°/7°E), computing RWY end and RWY beginning with a geodesic curve from RWY center, I find that I need a HDG change of about +/-0.05° to match the correct points.
Once I have beginning and endpoints, I compute the initial geodesic heading of the runway, and I am finally spot on. Though I cannot do that manually for all airports...
I have a feeling the actual value depends on LAT/LON and primary RWY HDG, but I do not see the relation yet.

if anyone has an input, idea, etc this is very appreciated!!

best regards
Jean Luc
 
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