VATSIM / IVAO / PILOTEDGE Users - Be aware of an important bug!

It’s not the altimetry system that compensates for temperature, it’s the flight guidance system. The altimeter will still show the same altitude, regardless of temperature.

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with live weather, the altitude bug is not fixed as of this latest hotfix. so far the temps look okay but we will see…

Exactly my thought, on the ATR and Embraer I’m flying its a FMS function it only compensates the FMS altitudes, the same you would be doing manually using temp correction table.

I’m afraid I don’t follow you; what part is not fixed?

-Matt | Working Title

the altitude reporting to 3rd party ATC controllers. it’s showing me about 1500ft above my indicated altitude. So far the ISA temps look good though and havent gone haywire… so that may be progress. hopefully I’m not speaking too soon.

Presently, it appears that third party ATC is using geometric altitude (the PLANE ALTITUDE simvar) to determine altitude, which will properly not match your indicated if the local pressures are not ISA.

-Matt | Working Title

from the sound of it then, they should be looking at a different SIMVAR? ISA+6 is acceptable at least, but it’s +6. better than +60 as it has been lol

To confirm – is it the controller that’s seeing the wrong altitude or a reporting map that you’re looking at as a player?

as of this time I’m using PEAware map from PilotEdge ,but AFIK that will be the same that the controller sees. I will be able to confirm that in about 60min as the network comes online.

Thanks. From the last couple days of this thread it seemed clear that ATC controllers on VATSIM see the pressure altitude, at least above transition altitude, but that some of the public maps like VATSPY show the plane altitude (GPS/geometric/true altitude)

This has lead to some confusion in past posts.

GPS altitude would seem reasonable, as that I believe is what ADS-B would transmit or a Mode/S transponder would transmit. I have no idea this is all over my head. I just know it worked before and now it’s gone bonkers lol. But so far I haven’t had any issues with the other problem with the temps being insane and my aircraft has been performing well so that’s a positive! : )

Transponders send pressure altitude. (I was surprised too, until I realized the purpose of the transponder is for air traffic control and they work with flight levels, which is based on pressure altitude!)

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ah ok. so maybe the 3rd party ATC providers need to update their client to look at the correct variable

Keep in mind that unless you were flying on one of the weather presets or happened to be at 29.92 in/Hg exactly, GPS altitude has never matched pressure altitude.

These maps may have always shown you a different altitude than you were expecting, but if nobody was checking them until the recent bug, they might not have noticed.

What would be great would be if we actually knew for sure exactly what variables are used by these apps in all places, but there’s no source or documentation for em. :smiley:


GPS altitude will never match pressure altitude anyway, at least in real life. Geometric (GPS) altitude is the altitude above the WGS84 ellipsoid, not above sea level.


I can confirm, flying over Antarctica in Live Weather, with an ISA of -45C, the Altitude Indicated was almost 2000 feet lower than the real airplane altitude. So things appears to be working properly on this SU5.

I haven’t checked any formula to see if the difference matched perfectly with calculations, but the effect is clearly there.

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Exactly, even with ADS-B the transponder sends out pressure altitude. The ATC station is able to convert this into an altitude (above msl) using the local QNH below the transition level (not transition altitude!). Above the pressure altitude is used directly (flight levels).

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Hello, tell me, have you fixed the height for the dispatchers of vatsim and ivao? do dispatchers now see the correct altitude as on the instruments?

we will find out in about 15 minutes when I check in

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If you scroll up a day you’ll find a couple people reporting that the ATC on VATSIM does see the correct pressure altitude which matches the indicated altitude in the cockpit when barometer is set to STD. There may be some small variances under transition altitude, but these appear to be correct and normal (since weather will not match exactly between MSFS and VATSIM)

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