Ruby script to calculate values about pressure.

calc_pressure.rb

#! /usr/local/bin/ruby
# coding: utf-8
#*********************************************
# Ruby script to calculate values about pressure.
#*********************************************
#
class CalcPressure
  # Constants
  C_1 = 0.0065
  C_2 = 273.15
  C_3 = 5.257

  # Calculate a sealevel pressure.
  def calc_sealevel(p, t, h)
    v   = 1 - (C_1 * h) / (t + C_1 * h + C_2)
    v **= C_3
    return p / v
  end

  # Calculate a pressure from a height above sea level.
  def calc_h2p(p, t, h)
    v   = 1 - (C_1 * h) / (t + C_1 * h + C_2)
    v **= C_3
    return p * v
  end

  # Calculate a height above sea level from a pressure.
  def calc_p2h(p_0, p, t)
    v  = (p_0 / p.to_f) ** (1 / C_3) - 1
    v *= t + C_2
    return v / C_1
  end

  # Calculate a temperature at the destination.
  def calc_temp_dest(t_a, h_a, h)
    return t_a - C_1 * (h - h_a)
  end
end

if __FILE__ == $0
  obj = CalcPressure.new

  # Calculate a sealevel pressure.
  p, t, h = 850, 15, 1729
  p_0 = obj.calc_sealevel(p, t, h)
  puts "P = #{p}, T = #{t}, h = #{h}"
  puts "P_0 = #{p_0}"
  puts "---"

  # Calculate a pressure from a height above sea level.
  p_0, t, h = 1015.25, 5, 1729
  p = obj.calc_h2p(p_0, t, h)
  puts "P_0 = #{p_0}, T = #{t}, h = #{h}"
  puts "P = #{p}"
  puts "---"

  # Calculate a height above sea level from a pressure.
  p_0, p, t = 1005.75, 900, 15
  h = obj.calc_p2h(p_0, p, t)
  puts "P_0 = #{p_0}, p = #{p}, T = #{t}"
  puts "h = #{h}"
  puts "---"

  # Calculate a temperature at the destination.
  t_a, h_a, h = 15, 1729, 0
  t = obj.calc_temp_dest(t_a, h_a, h)
  puts "T_a = #{t_a}, h_a = #{h_a}, h = #{h}"
  puts "T = #{t}"
end