A/A Radar and altimeter setting?

[norman99]

I have a question regarding the A/A radar modes of the Hornet. Are the altitudes given, (both TDC scan range, & contact alt) referencing the current aircraft's altimeter setting?

 

For instance, I have a mission in Nevada with custom weather. QNH on the ground at Nellis is 30.15. Unfortunately as the AI doesn't adjust their altimeter's for pressure changes, (they fly an "absolute true" altitude so to speak), the tanker in the mission that should be at 20,000ft, is actually flying at 19,000ft indicated altitude. 

 

When locked with the radar however, it indicates an altitude of 20,000, despite my aircraft's altimeter being corrected for the QNH, and indicating 19,000ft.

 

 

Is this correct? Are the altitudes on the radar "magically" correct, regardless of air pressure (ie, it uses the same "absolute true" altitude that AI use?) How does the real radar function? Does it receive "corrected" (ie adjusted by the altimeter setting) altitude from the aircraft's altimeter?

Edited April 8, 2021 by norman99

[Tholozor]

The data blocks at the bottom of the radar format reference your aircraft's airspeed and altitude.

[Machalot]

1 hour ago, norman99 said:

When locked with the radar however, it indicates an altitude of 20,000, despite my aircraft's altimeter being corrected for the QNH, and indicating 19,000ft.

That's interesting.  I wonder if the radar numbers are given in terms of Mean Sea Level, which is a commonly used geometric altitude (what you probably meant by "true").  MSL altitude is calculated using data from the aircraft's INS.  You could try turning off the INS to see if it makes a difference. 

Edited April 8, 2021 by Machalot

[Harker]

You might want to take a look at this, might help answer some of your questions.
https://forums.eagle.ru/topic/242391-investigating-baro-altitude-value-for-calculations-not-taken-from-cockpit-altimeter/

[norman99]

Thanks, exactly what I was looking for. I'll add my thoughts to that discussion.