Runway postionning

Discussion related to terrain/scenery design.
JeeHell
Posts: 65
Joined: Sun Jan 15, 2012 11:04 pm

Runway postionning

Postby JeeHell » Tue Nov 07, 2017 4:17 pm

Hello LM team,

I am trying to match runway positions in P3D with custom objects, injected in the rendering engine at realtime (lightgroups, cubes, etc...).
However, I found that there are slight angle differences between what I position programmatically, and the actual runway seen in P3D.

I use the XML declared runway center LAT/LON, length and True HDG as a reference point, and compute with a WGS84 library what the runway ends LAT/LON would be. However, this gives me in some cases more than 0.05° of difference (this may not seem big, but on a 3000m runway, this means quite a difference (1.3 m or so, see this picture http://163.172.86.18/lights.jpg the lights should be exactly on the RWY edge white lines).
I have tried spherical computations (great circle) and the difference is there as well.
If I extract the runway ends myself (using the LAT/LON from P3D with simconnect), I can compute the true heading, which differs, then using that HDG I find again the center position with a good accuracy.
Though, I cannot do that manually for the 20000+ airports...

Are you able to help me out here with how P3D uses the XML data to actually draw the runway object?

Thanks a lot!
Jean Luc

JeeHell
Posts: 65
Joined: Sun Jan 15, 2012 11:04 pm

Re: Runway postionning

Postby JeeHell » Thu Nov 09, 2017 9:29 pm

I have made many tests, including using the new render objects in the PDK.
If I use WGS84 coordinates to place lines, I can match with nanometer accuracy the runway ends as long as I have the correct initial LAT/LON/HDG...
So my only guess right now is that P3D runways do not use WGS84 computations in the texture drawing engine, or in the BGL data extraction.
I can understand you cannot disclose the code etc... but at least a hint to help find the solution here would help...

Best regards
Jean Luc

JeeHell
Posts: 65
Joined: Sun Jan 15, 2012 11:04 pm

Re: Runway postionning

Postby JeeHell » Wed Nov 15, 2017 1:05 pm

LM team,

This is really a concern for me.
You are implementing a lot of nice features to turn P3D into a versatile simulation platform, with many new features in the PDK a lot of us have dreamed for a long time. But the outside world is still the most important part in the platform itself.
There are many tools which can need an accurate runway position such as
-HUD
-lighting systems
-navigation systems
-...

If I have a discrepancy of this magnitude, this is really bad. If I make my own scenery, then I have no certainty to it's visual depiction...

Best regards
Jean Luc

User avatar
WarpD
Posts: 1246
Joined: Mon Feb 14, 2011 5:29 am

Re: Runway postionning

Postby WarpD » Wed Nov 15, 2017 8:05 pm

Since headings can contain fractional values, are you certain you're getting the correct heading value that is in the physical scenery BGL for the airport?
Ed Wilson
Senior Developer
Mindstar Aviation

JeeHell
Posts: 65
Joined: Sun Jan 15, 2012 11:04 pm

Re: Runway postionning

Postby JeeHell » Wed Nov 15, 2017 8:36 pm

Since headings can contain fractional values, are you certain you're getting the correct heading value that is in the physical scenery BGL for the airport?
Yes, I am sure, I am talking about <0.05°differences, not gross rounding errors of 0.5° or more.
I checked with data extracted from BGL files directly, as well as from ADE.

JeeHell
Posts: 65
Joined: Sun Jan 15, 2012 11:04 pm

Re: Runway postionning

Postby JeeHell » Fri Apr 20, 2018 3:34 pm

Hello LM team

I would like to revive this thread as I could not find a proper way to match BGL runway data and real-time sim display.
I need a way to accurately position one end of the runway and get the initial true orthodromic heading from that point.

Thanks.
Jean Luc

tomm
Posts: 1
Joined: Thu Jul 12, 2018 11:56 am

Re: Runway postionning

Postby tomm » Thu Jul 12, 2018 12:01 pm

I have a similar concern. I export the position of the simulated plane to another application. Suppose the plane is on the runway, ready for takeoff. When I use that position to show the position of a plane on a map, the plane is not even sitting on the runway. It _is_ sitting on the runway if I position my plane on large airports such as London Heathrow, KLAX, ... This is not so on smaller aerodromes.

Is it possible that better accuracy is guaranteed close to bigger airports?


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