src/Computer/LiftDatabaseComputer.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 "LiftDatabaseComputer.hpp"
  25 #include "Engine/Navigation/TraceHistory.hpp"
  26 #include "NMEA/LiftDatabase.hpp"
  27 #include "NMEA/MoreData.hpp"
  28 #include "NMEA/CirclingInfo.hpp"
  29 #include "Util/Clamp.hpp"
  30
  31 void
  32 LiftDatabaseComputer::Clear(LiftDatabase &lift_database,
  33                             TraceVariableHistory &circling_average_trace)
  34 {
  35   lift_database.Clear();
  36
  37   circling_average_trace.clear();
  38 }
  39
  40 void
  41 LiftDatabaseComputer::Reset(LiftDatabase &lift_database,
  42                             TraceVariableHistory &circling_average_trace)
  43 {
  44   last_circling = false;
  45   last_heading = Angle::Zero();
  46
  47   Clear(lift_database, circling_average_trace);
  48 }
  49
  50 /**
  51  * This function converts a heading into an unsigned index for the LiftDatabase.
  52  *
  53  * This is calculated with Angles to deal with the 360 degree limit.
  54  *
  55  * 357 = 0
  56  * 4 = 0
  57  * 5 = 1
  58  * 14 = 1
  59  * 15 = 2
  60  * ...
  61  * @param heading The heading to convert
  62  * @return The index for the LiftDatabase array
  63  */
  64 static unsigned
  65 heading_to_index(Angle &heading)
  66 {
  67   static constexpr Angle afive = Angle::Degrees(5);
  68
  69   unsigned index = (unsigned)
  70       ((heading + afive).AsBearing().Degrees() / 10);
  71
  72   return Clamp(index, 0u, 35u);
  73 }
  74
  75 void
  76 LiftDatabaseComputer::Compute(LiftDatabase &lift_database,
  77                               TraceVariableHistory &circling_average_trace,
  78                               const MoreData &basic,
  79                               const CirclingInfo &circling_info)
  80 {
  81   // If we just started circling
  82   // -> reset the database because this is a new thermal
  83   if (!circling_info.circling && last_circling)
  84     Clear(lift_database, circling_average_trace);
  85
  86   // Determine the direction in which we are circling
  87   bool left = circling_info.TurningLeft();
  88
  89   // Depending on the direction set the step size sign for the
  90   // following loop
  91   Angle heading_step = left ? Angle::Degrees(-10) : Angle::Degrees(10);
  92
  93   const Angle heading = basic.attitude.heading;
  94
  95   // Start at the last heading and add heading_step until the current heading
  96   // is reached. For each heading save the current lift value into the
  97   // LiftDatabase. Last and current heading are included since they are
  98   // a part of the ten degree interval most of the time.
  99   //
 100   // This is done with Angles to deal with the 360 degrees limit.
 101   // e.g. last heading 348 degrees, current heading 21 degrees
 102   //
 103   // The loop condition stops until the current heading is reached.
 104   // Depending on the circling direction the current heading will be
 105   // smaller or bigger then the last one, because of that negative() is
 106   // tested against the left variable.
 107   for (Angle h = last_heading;
 108        left == negative((heading - h).AsDelta().Degrees());
 109        h += heading_step) {
 110     unsigned index = heading_to_index(h);
 111     lift_database[index] = basic.brutto_vario;
 112   }
 113
 114   // detect zero crossing
 115   if ((heading < Angle::QuarterCircle() &&
 116        last_heading.Degrees() > fixed(270)) ||
 117       (last_heading < Angle::QuarterCircle() &&
 118        heading.Degrees() > fixed(270))) {
 119
 120     fixed h_av = fixed(0);
 121     for (auto i : lift_database)
 122       h_av += i;
 123
 124     h_av /= lift_database.size();
 125     circling_average_trace.push(h_av);
 126   }
 127
 128   last_circling = circling_info.circling;
 129   last_heading = basic.attitude.heading;
 130 }