When in the vicinity of an Aerodrome the vertical position should be expressed as height. This is done by using the QFE setting.
Therefore, when on the ground the altimeter should display 0ft.
AIP ENR 1.7
At high altitude aerodromes, approaching 10,000ft, it can be impossible to set the appropriate subscale for QFE and therefore at those aerodromes QNH is used instead.
