GetStandardAtmPressure Function

  function GetStandardAtmPressure(Altitude) result(StandardAtmPressure)
    !+ Return standard atmosphere barometric pressure, given the elevation (altitude).
    !+ Reference:
    !+ ASHRAE Handbook - Fundamentals (2017) ch. 1 eqn 3

    real, intent(in)  ::  Altitude
      !+ Altitude in ft [IP] or m [SI]
    real              ::  StandardAtmPressure
      !+ Standard atmosphere barometric pressure in Psi [IP] or Pa [SI]

    if (isIP()) then
        StandardAtmPressure = 14.696 * (1.0 - 6.8754e-06 * Altitude)**5.2559
    else
        StandardAtmPressure = 101325 * (1 - 2.25577e-05 * Altitude)**5.2559
    end if
  end function GetStandardAtmPressure