pressure = stdatm(elevation)
This function converts elevation in meters to atmospheric pressure in hPa using the pressure-elevation relationship in the ICAO Standard Atmosphere:
where sea level pressure hPa; sea level temperature K; and the adiabatic lapse rate K m. is the molar weight of air, the acceleration due to gravity, and the gas constant, giving 0.03417 K m.
For further discussion see:
Stone, J., 2000. Air pressure and cosmogenic isotope production. Journal of Geophysical Research 106, pp. 23,753-23,759.