Airfield elevation issue?

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JarangMandi
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Joined: Thu Apr 13, 2017 10:20 am

Airfield elevation issue?

Postby JarangMandi » Fri Nov 17, 2017 12:04 am

Sorry Peter - another one from our testing tonight...

This one appears to relate to different airfield elevations between simulations.

I was in XP11.10b7; my colleague was in P3Dv2. We were both parked at Bristol. He was at 625ft AMSL, I was at 602ft AMSL on account of having "runway follows contours" turned on.

Whilst his JoinFS instance was being sent my "real" altitude as confirmed through the "Aircraft" dialog, in his simulator he saw me rise out of the ground and then keep rising to around 800ft before I disappeared below ground again and the cycle repeated. All non-JoinFS software he had attached to his simulation reported the same (as you'd expect it to). I was completely stationary - no engines running and parking brake set.

My guess is that I was getting a vertical speed from somewhere through being moved at his end from below the ground to being level with it, and that vertical speed was retained and used to modify my altitude in his sim until such time as it got a new position / altitude update. The issue went away when I taxiied to a part of the runway at the same elevation as his scenery - and of course when I turned "runway follows contours" off - both of these scenarios resulted in us being at the same altitude AMSL so there was no correction going on.

We probably didn't do enough testing to work out the effect that the "Elevation Correction" option had on things, but it changed nothing when I flipped the state from "off" to "on".

That's it for tonight! :)

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Peter
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Joined: Fri Sep 23, 2016 8:51 am

Re: Airfield elevation issue?

Postby Peter » Fri Nov 17, 2017 8:25 am

Thanks. Yes, I've seen this one as while getting the XP support in. As you say it's because of the elevation issue, but has become more of a problem because of the greater differences between the sims. I've been meaning to fix that problem for a while now anyway, so this seems like a good opportunity to do so.

Peter

webcanic
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Joined: Sat Oct 15, 2016 4:59 pm

Re: Airfield elevation issue?

Postby webcanic » Sun Dec 31, 2017 3:21 pm

Hi Peter.
I wish you one happy New Year.

I fly, with my team since a long time, with JoinFS.
We use all the types of flight simulators, FSX, P3D (V3 & V4), X-Plane.

With JoinFS release 1.3.6, we had an automatic level rectification of aircraft on the ground.
In the landing, when a plane approached the runway, all the observers could see it landing on the runway with the good level trajectory.

After the release 1.3.6, the plane approaches the airport, and falls brutally at the level of the runway, before touching it. :o
I think that the problem is in relation with the difference of altimetry between the pilot and the other players.
It’s the eternal problem of mesh files in the simulators.

Did you observe this problem?

Best regards,
John, in west of France

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Peter
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Joined: Fri Sep 23, 2016 8:51 am

Re: Airfield elevation issue?

Postby Peter » Sun Dec 31, 2017 5:57 pm

Hi John,

the elevation correction code was changed in 1.3.4. The odd thing is that it was intended to make it more reliable and smoothed out over a range of altitude. So it appears that it might not be working as intended.

Are you able to determine which aircraft are suffering from the problem. Do all network aircraft suddenly drop? I suspect that it might just be X-Plane flown aircraft, could you confirm that?

Peter


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