src/Computer/AutoQNH.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 "AutoQNH.hpp"
  25 #include "NMEA/Info.hpp"
  26 #include "NMEA/Derived.hpp"
  27 #include "Settings.hpp"
  28 #include "Engine/Waypoint/Waypoints.hpp"
  29
  30 void
  31 AutoQNH::Process(const NMEAInfo &basic, DerivedInfo &calculated,
  32         const ComputerSettings &settings_computer, const Waypoints &way_points)
  33 {
  34   if (!calculated.flight.on_ground // must be on ground
  35       || IsFinished()    // only do it once
  36       || !basic.location_available // Reject if no valid GPS fix
  37       || !basic.static_pressure_available // Reject if no pressure
  38       || settings_computer.pressure_available // Reject if QNH already known
  39     ) {
  40     if (!IsFinished())
  41       Reset(); // restart if havent performed
  42
  43     return;
  44   }
  45
  46   if (!IsFinished())
  47     countdown_autoqnh--;
  48
  49   if (!countdown_autoqnh) {
  50     if (CalculateQNH(basic, calculated, way_points))
  51       countdown_autoqnh = UINT_MAX; // disable after performing once
  52     else
  53       Reset();
  54   }
  55 }
  56
  57 void
  58 AutoQNH::Reset()
  59 {
  60   countdown_autoqnh = QNH_TIME;
  61 }
  62
  63 inline bool
  64 AutoQNH::CalculateQNH(const NMEAInfo &basic, DerivedInfo &calculated,
  65                       const Waypoints &way_points)
  66 {
  67   const Waypoint *next_wp;
  68   next_wp = way_points.LookupLocation(basic.location, fixed(1000));
  69
  70   if (next_wp && next_wp->IsAirport())
  71     CalculateQNH(basic, calculated, next_wp->elevation);
  72   else if (calculated.terrain_valid)
  73     CalculateQNH(basic, calculated, calculated.terrain_altitude);
  74   else
  75     return false;
  76
  77   return true;
  78 }
  79
  80 inline void
  81 AutoQNH::CalculateQNH(const NMEAInfo &basic, DerivedInfo &calculated,
  82                       fixed altitude)
  83 {
  84   calculated.pressure = AtmosphericPressure::FindQNHFromPressure(basic.static_pressure, altitude);
  85   calculated.pressure_available.Update(basic.clock);
  86 }