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Atitude not matching


Biga42
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Flying a mission in PG looking for the tanker, I realized that was a difference between in altitude comparing with altitude informed by the tanker. comparing with the map view, the altitude shown in the map does not match with the altitude shown in the Hornet. This mission was started in the air. See pictures attatched.

 

 

mapa.png

hud.png

altimeter.png

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The altitude in the Mission Editor is a magic number that represents the absolute distance between the aircraft and exact sea level. This isn't a number that has any real equivalent in the real word or gauges we have in the cockpit, as there is no such thing as an exact sea level, and there is no way to reliably measure an aircraft's exact altitude above sea level. 

 

You can think of the Mission Editor altitude as a bit of a peak behind the curtain at what the game engine sees. Since it's a simulator, the altitude you see in the cockpit is derived from the absolute altitude based on the local barometric pressure, temperature, and your altimeter setting. 

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14 hours ago, Bunny Clark said:

The altitude in the Mission Editor is a magic number that represents the absolute distance between the aircraft and exact sea level. This isn't a number that has any real equivalent in the real word or gauges we have in the cockpit, as there is no such thing as an exact sea level, and there is no way to reliably measure an aircraft's exact altitude above sea level. 

 

You can think of the Mission Editor altitude as a bit of a peak behind the curtain at what the game engine sees. Since it's a simulator, the altitude you see in the cockpit is derived from the absolute altitude based on the local barometric pressure, temperature, and your altimeter setting. 

This is the kind of thoughtful answer that’s very helpful. Thank you. 

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10 hours ago, Biga42 said:

yes, but the tanker is supposed to be at angels 20 and it is in the map view but not in the air....imagine you looking for a tanker at night with no NVG with 2000 feet altitude difference.....

 

I think it might be a bug.

It's not a bug, you're misunderstanding what the numbers mean. When you set an aircraft in the mission editor to 20,000 feet, they are placed 20,000 feet above the "0" elevation mark on the map. What does that "0" altitude correlate to? Whatever the person who built the map geometry decided it was. It should be roughly mean sea level, but of course in the real world sea level fluctuates based on the position of the Moon and Sun, the winds, and the water temperature, so there's no "real" exact sea level. In a DCS map "sea level" is an arbitrary point determined by the map creator, especially on a map with seas, which is most of them. Then once in an airplane, you measure your altitude above mean sea level by measuring the air pressure outside the plane. But because atmospheric pressure fluctuates with the weather and temperature, this needs to be calibrated every time you fly (really, multiple times per flight) by referencing the current pressure on the ground at a location with a determined height, typically an airport. But that still doesn't get you a reliable measurement because atmospheric pressure varies from place to place, and doesn't always decrease linearly as you increase altitude. Depending on how the exterior pressure is measured the gauge can also fluctuate with airspeed. 

 

So the problem isn't that the game is placing your aircraft at a different altitude than you set it to. It's placing the aircraft exactly where you set it to, but your cockpit gauges aren't measuring altitude accurately - which is 100% realistic.  This is a challenge for real pilots every day. It's why air corridors are separated by at least 500 feet in altitude. You can minimize the discrepancy by setting your altimeter up correctly. In your F-16 screenshot I can see that the barometric altimeter is reading lower than the radar altimeter, which is a sure sign that your barometric altimeter is set incorrectly (unless you're flying over Death Valley). 

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when the tanker states that it is at 20.000 ft for approaching for refuel, it should not be at 18A....and I understand the above 5.000ft we shall set altimeter to 29.92....so everyone is set at same baro including the tanker. Inmy first picture you can see that the tanker is at about 18A.

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22 hours ago, Bunny Clark said:

In your F-16 screenshot I can see that the barometric altimeter is reading lower than the radar altimeter, which is a sure sign that your barometric altimeter is set incorrectly (unless you're flying over Death Valley). 

 

You mean the "R19880"?? How can a radar altitude work that high? Unrealistic.

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5 hours ago, Joni said:

 

You mean the "R19880"?? How can a radar altitude work that high? Unrealistic.

The F-16 is equipped with the AN/APN-232 Combined Altitude Radar Altimeter, which is rated to operate up to 50,000ft.

The F/A-18 is equipped with the AN/APN-194 Radar Altimeter Set, which is only rated to operate up to 5,000ft.


Edited by Tholozor
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REAPER 51 | Tholozor
VFA-136 (c.2007): https://www.digitalcombatsimulator.com/en/files/3305981/
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36 minutes ago, Tholozor said:

The F-16 is equipped with the AN/APN-232 Combined Altitude Radar Altimeter, which is rated to operate up to 50,000ft.

The F/A-18 is equipped with the AN/APN-194 Radar Altimeter Set, which is only rated to operate up to 5,000ft.

 

 

OMG, I didn't know. Thanks.

 

That's one hell of a spec there.

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15 hours ago, Biga42 said:

when the tanker states that it is at 20.000 ft for approaching for refuel, it should not be at 18A....

Yah, that's a separate, though related, issue. When we call the tanker on the radio in game it should really report it's altitude based on the current pressure altitude, not absolute altitude.

 

 

6 hours ago, Joni said:

OMG, I didn't know. Thanks.

 

That's one hell of a spec there.

Yah, that's one thing I really like about the Viper, being able to always see rad and baro alt on the HUD together is great, rather than needing to fiddle with a switch or get an annoying flashing B whenever I'm above 5,000 feet. 

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It's also a big problem for airspace deconfliction. If you have elements of a strike package separated vertically by a thousand feet, but the altitude of the waypoints is in "feet above an arbitrary zero altitude" and not "feet above MSL", even setting the baro altimeter to 29.92 doesn't keep you deconflicted from the AI, with the difference being what it is.

 

The current fix seems to be for the mission designer to figure out what the difference is between the ME altitude for each element and what the player thinks the assigned altitude is based on the instruments in the cockpit and adjust accordingly. It adds a step that shouldn't be necessary.

Very Respectfully,

Kurt "Yoda" Kalbfleisch

London

"In my private manual I firmly believed the only time there was too much fuel aboard any aircraft was if it was fire." --Ernest K. Gann

 

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