Converts a station barometric pressure to pressure altitude using the ICAO/NOAA International Standard Atmosphere barometric formula.
Published for review. The Founder is checking every card himself; anything he strikes comes down the same hour.
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Inputs
station_pressure_hpa (number, hPa (millibars), required) min 300 max 1,100 : Station (unadjusted) barometric pressure.
Outputs
pressure_altitude_ft (feet): Pressure altitude.
Steps
ISA barometric formula: PA = (1 - (P / 1013.25)^0.190284) * 145366.45, where P is station pressure in hPa and PA is pressure altitude in feet, and 1013.25 hPa is the ICAO standard sea-level pressure.
Round to 2 decimals.
This assumes the ICAO Standard Atmosphere's fixed temperature lapse rate; actual pressure altitude readouts from an altimeter use this same formula.
Constants
standard_sea_level_pressure_hpa = 1013.25 hPa (source: ICAO Standard Atmosphere barometric formula for pressure altitude)
isa_exponent = 0.190284 dimensionless (source: ICAO Standard Atmosphere barometric formula for pressure altitude)
isa_feet_constant = 145366.45 feet (source: ICAO Standard Atmosphere barometric formula for pressure altitude)
Sources
ICAO Standard Atmosphere barometric formula for pressure altitude (International Civil Aviation Organization (ICAO); formula also published by NOAA/FAA, 2026-09-30T19:55:00Z) - Standard pressure-altitude formula used in aviation and meteorology.