Thanks for that BlueLine
However, I am now confused about the difference between QFF and QNH. It seems to me that your definition of QFF is my definition of QNH -
"QNH is what the pressure would be if we could go vertically down from here to the level of the sea".
Ah, is yours much more location-specific somehow?
I remember the definition of absolute altitude I learnt now, "the independently measured altitude of the aeroplane AMSL with no errors, or all errors perfectly accounted for".
Sound right?
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Confident, cocky, lazy, dead.