barometric error

barometric error

barometric errorclick for a larger image
Altimeter indications at both locations are same though the heights above sea level are different.
An error in the pressure altimeter resulting from a difference between the prevalent barometric pressure and that in the standard atmosphere. The local barometric pressure is corrected to sea level on the subscale, or veedor counter Kollsman window, before or during flight. The aircraft height even after this correction will vary if it flies into an area of higher or lower pressure. For this reason, during cross-country flights above the transition altitude, standard altimeter settings (1013.2 hectopascals, 760 mm, or 29.92 in) are set. (See also Kollsman window.