The Aeronautical Pressure Correction is derived by the method
defined in the Smithsonian Meteorological Tables as follows:
pow(x, y) is the power function and gives x raised to the y power.
elev is the station elevation.
pres is the absolute pressure reading.
cpres is the calibrated pressure.
cpres = pres * pow((1.0 + 0.000084229 * (elev/pow(pres, 0.19028))), 5.2553);