AGL corrected

[Achoriham]

Hi,

 

Perhaps a very basic question but unfortunately I don't find the solution...

 

What would be the right FSUIPC offset for altitude (AGL) but corrected with the actual QNH?

I mean, say the A/C flies at 10000 ft but that would be corrected for the present QNH?

 

I tried 0x0574 but it seems to be not corrected for QNH.

 

thanks in advance

 

regards

Achoriham

[Pete Dowson]

What would be the right FSUIPC offset for altitude (AGL) but corrected with the actual QNH?

I mean, say the A/C flies at 10000 ft but that would be corrected for the present QNH?

 

I tried 0x0574 but it seems to be not corrected for QNH.

 

I don't understand what you want. The altitude in the 64-bit value at 0570 is the ACTUAL altitude above mean sea level, not above ground. If you want the true AGL just subtract the current ground level from that (i.e. the value at offset 0020). The current atmospheric pressure doesn't change your altitude above ground at all.

 

You can also read the AGL at lower levels, when the radio altitude instrument is valid, at offset 31E4.

 

If you really want to know what the ALTIMETER shows with the QNH set to the value in offset 0330, then this is given at offset 3324.

 

If you want the PA (Pressure Altitude), ie the altimeter reading when the pressure is set to STD (1013.2 hPa), then this is at offset 34B0.

 

I can't imagine what else it is you might want.

 

Pete

[Achoriham]

I don't understand what you want. The altitude in the 64-bit value at 0570 is the ACTUAL altitude above mean sea level, not above ground. If you want the true AGL just subtract the current ground level from that (i.e. the value at offset 0020). The current atmospheric pressure doesn't change your altitude above ground at all.

 

You can also read the AGL at lower levels, when the radio altitude instrument is valid, at offset 31E4.

 

If you really want to know what the ALTIMETER shows with the QNH set to the value in offset 0330, then this is given at offset 3324.

 

If you want the PA (Pressure Altitude), ie the altimeter reading when the pressure is set to STD (1013.2 hPa), then this is at offset 34B0.

 

I can't imagine what else it is you might want.

 

Pete

 

Hi Pete,

 

Many thanks for your answer.

In your explanation I just got from you what I wanted.

 

Happy Xmas

 

Achoriham