src/Atmosphere/Pressure.cpp

   1 /*
   2 Copyright_License {
   3
   4   XCSoar Glide Computer - http://www.xcsoar.org/
   5   Copyright (C) 2000-2013 The XCSoar Project
   6   A detailed list of copyright holders can be found in the file "AUTHORS".
   7
   8   This program is free software; you can redistribute it and/or
   9   modify it under the terms of the GNU General Public License
  10   as published by the Free Software Foundation; either version 2
  11   of the License, or (at your option) any later version.
  12
  13   This program is distributed in the hope that it will be useful,
  14   but WITHOUT ANY WARRANTY; without even the implied warranty of
  15   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16   GNU General Public License for more details.
  17
  18   You should have received a copy of the GNU General Public License
  19   along with this program; if not, write to the Free Software
  20   Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
  21 }
  22 */
  23
  24 #include "Pressure.hpp"
  25
  26 #define k1 fixed(0.190263)
  27 #define inv_k1 fixed(1.0 / 0.190263)
  28 #define k2 fixed(8.417286e-5)
  29 #define inv_k2 fixed(1.0 / 8.417286e-5)
  30
  31 AtmosphericPressure
  32 AtmosphericPressure::QNHAltitudeToStaticPressure(const fixed alt) const
  33 {
  34   return HectoPascal(pow((pow(GetHectoPascal(), k1) - k2 * alt), inv_k1));
  35 }
  36
  37 AtmosphericPressure
  38 AtmosphericPressure::PressureAltitudeToStaticPressure(const fixed alt)
  39 {
  40   return Standard().QNHAltitudeToStaticPressure(alt);
  41 }
  42
  43
  44 fixed
  45 AtmosphericPressure::StaticPressureToQNHAltitude(const AtmosphericPressure ps) const
  46 {
  47   return (pow(GetHectoPascal(), k1) - pow(ps.GetHectoPascal(), k1)) * inv_k2;
  48 }
  49
  50 fixed
  51 AtmosphericPressure::PressureAltitudeToQNHAltitude(const fixed alt) const
  52 {
  53   return StaticPressureToQNHAltitude(PressureAltitudeToStaticPressure(alt));
  54 }
  55
  56 fixed
  57 AtmosphericPressure::QNHAltitudeToPressureAltitude(const fixed alt) const
  58 {
  59   return StaticPressureToPressureAltitude(QNHAltitudeToStaticPressure(alt));
  60 }
  61
  62 fixed
  63 AtmosphericPressure::StaticPressureToPressureAltitude(const AtmosphericPressure ps)
  64 {
  65   return Standard().StaticPressureToQNHAltitude(ps);
  66 }
  67
  68 AtmosphericPressure
  69 AtmosphericPressure::FindQNHFromPressure(const AtmosphericPressure pressure,
  70                                          const fixed alt_known)
  71 {
  72   return pressure.QNHAltitudeToStaticPressure(-alt_known);
  73 }