Atitude not matching

[Biga42]

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.

 

 

[Svend_Dellepude]

It's been like this forever. Not sure why though. Might be some discrepancy between real and baro altitude.

[Swift.]

iirc, this is because the F10 map is showing a geometric altitude as spat out by the game engine. Whereas the altimeter accounts for pressure and density change and what have you.

[Bunny Clark]

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. 

[Biga42]

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.

[Biga42]

same mission with the AV8B:

Tanker map altitude

 

 

Harrier Map Altitude

 

Harrier HUD

 

 

Harrier Altimeter

 

[Biga42]

Now with the F16....same problem as Hornet:

 

[Hobo 1-1]

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. 

[Bunny Clark]

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). 

[Biga42]

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.

[Joni]

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.

[Tholozor]

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 December 26, 2020 by Tholozor

[Joni]

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.

[Bunny Clark]

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. 

[Yoda967]

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.

[Grodin]

Still an issue, very annoying for example on kola map waypoint is at 20k but the plane altimeter show 22k.

[norman99]

On 12/25/2020 at 3:47 AM, Bunny Clark said:

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.

Sorry, but I completely disagree with this take.

Honestly, it's that the interaction between atmospheric modelling and AI unit behaviour (and mission editor) is almost non existent. This is the crutch of the issue. AI are simply oblivious to the realities of temp/pressure and how they affect the indicated altitude. If a unit is set to fly at 20K in the mission editor, most users would expect that so long as they use the correct altimeter setting, the AI would appear in game at 20K, not +/- 3000'.

It's most likely the result of a game engine that dates back decades, and the therefore core changes become almost impossible. Just something we have to live with unfortunately.

[Pillowcat]

6 minutes ago, norman99 said:

most users would expect that so long as they use the correct altimeter setting

But they actually not. This can be a space to become better in pilot wises lol.

Spoiler

 

[norman99]

17 hours ago, Pillowcat said:

But they actually not. This can be a space to become better in pilot wises lol.

Mate, respectfully, you are completely missing the point. I am well aware how temp/pressure changes affect the ‘true’ altitude of an aircraft. What you are showing is how temperature affects indicated altitude, great. But ALL aircraft are operated based on indicated altitude and accept that the ‘true’ altitude will differ, not the other way around. (The only exception is low temperature altimetery corrections applied during cold weather ops, ISA-15°C, which I am personally very familiar with.)

It’s not a matter of becoming a better pilot.

If I set my altimeter to 29.92/1013, and fly at 20,000ft, my actual altitude will be whatever it is on the day, I actually don’t care. What I do care about is wether all the other aircraft in my vicinity are using the same altimeter setting, therefore allowing indicated altitude to be used to accurately seperate/deconflict seperate flights, just as is done in the real world, both civil and military.

Currently only user/user separation can be planned this way. Presently there is no way to get AI aircraft to fly at a preplanned altitude in a realistic manner, ie fly a constant 20,000K on their simulated altimeter, regardless of what the temp/pressure and resultant ‘true’ altitude is.

As an example, the following is currently impossible. Imagine a scenario with a requirement to minimise emissions, so no comms and radars off. At a pre-briefed point you are planning to rejoin on a tanker, one of 3 stacked 2000’ apart at 20K, 22K and 24K. The 3 tankers won’t be where you expect them to be because they don’t simulate flying at an indicated altitude. Even if you do find one, unless you visually acquire all 3, you’ll have no idea which tanker it is. This is because their altitude is hard coded to be the ‘true’ DCS altitude all the time.

This needs to be changed to be realistic.

[Pillowcat]

1 hour ago, norman99 said:

you are completely missing the point

Look the message which popped this topic after 4 years gap, look at the first message. Yeah there is (or was) controversial AI behavior, but people whipping altimeter readings.

Spoiler

 

 

Edited January 22 by Pillowcat

[norman99]

@Pillowcat I did read the first post.

I agree that the question "why is my altimeter reading 18K when I set the tanker to 20K" is the wrong question.  It should be "why is the tanker at 18K when I set it to fly at 20K."

With that said, it doesn't really matter which way the question was asked, there's a long standing issue in DCS, and it's way overdue being addressed.