src/Geo/Math.hpp

   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 /*! @file
  25  * @brief Library for calculating Earth dimensions
  26  *
  27  * This library provides general functions for calculating dimensions
  28  * on the Earth with GPS coordinates.
  29  */
  30
  31 #ifndef XCSOAR_GEO_MATH_HPP
  32 #define XCSOAR_GEO_MATH_HPP
  33
  34 #include "Math/fixed.hpp"
  35 #include "Math/Angle.hpp"
  36 #include "Constants.hpp"
  37 #include "Compiler.h"
  38
  39 struct GeoPoint;
  40
  41 /**
  42  * Convert a distance on earth's surface [m] to the according Angle,
  43  * assuming the earth is a sphere.
  44  */
  45 constexpr
  46 static inline Angle
  47 EarthDistanceToAngle(fixed distance)
  48 {
  49   return Angle::Radians(distance / REARTH);
  50 }
  51
  52 /**
  53  * Convert an angle to the according distance on earth's surface [m],
  54  * assuming the earth is a sphere.
  55  */
  56 constexpr
  57 static inline fixed
  58 AngleToEarthDistance(Angle angle)
  59 {
  60   return angle.Radians() * REARTH;
  61 }
  62
  63 /**
  64  * Finds cross track error in meters and closest point P4 between P3
  65  * and desired track P1-P2.  Very slow function!
  66  */
  67 fixed
  68 CrossTrackError(const GeoPoint &loc1, const GeoPoint &loc2,
  69                 const GeoPoint &loc3, GeoPoint *loc4);
  70
  71 /**
  72  * Calculates projected distance from P3 along line P1-P2.
  73  */
  74 gcc_pure
  75 fixed
  76 ProjectedDistance(const GeoPoint &loc1, const GeoPoint &loc2,
  77                   const GeoPoint &loc3);
  78
  79 void
  80 DistanceBearing(const GeoPoint &loc1, const GeoPoint &loc2,
  81                 fixed *distance, Angle *bearing);
  82
  83 /**
  84  * Calculates the distance between two locations
  85  * @param loc1 Location 1
  86  * @param loc2 Location 2
  87  * @return The distance
  88  */
  89 gcc_pure
  90 fixed
  91 Distance(const GeoPoint &loc1, const GeoPoint &loc2);
  92
  93 /**
  94  * Calculates the bearing between two locations
  95  * @param loc1 Location 1
  96  * @param loc2 Location 2
  97  * @return The bearing
  98  */
  99 gcc_pure
 100 Angle
 101 Bearing(const GeoPoint &loc1, const GeoPoint &loc2);
 102
 103 /**
 104  * Finds the point along a distance dthis (m) between p1 and p2, which are
 105  * separated by dtotal.
 106  *
 107  * This is a slow function.  Adapted from The Aviation Formulary 1.42.
 108  */
 109 gcc_pure
 110 GeoPoint
 111 IntermediatePoint(const GeoPoint &loc1, const GeoPoint &loc2,
 112                   const fixed dthis);
 113
 114 /**
 115  * Find the nearest great-circle middle point between the two.
 116  */
 117 gcc_pure
 118 GeoPoint
 119 Middle(const GeoPoint &a, const GeoPoint &b);
 120
 121 /**
 122  * Calculate and add distances between point 1 and 2, and point 2 and 3.
 123  *
 124  * @param loc1 Location 1
 125  * @param loc2 Location 2
 126  * @param loc3 Location 3
 127  *
 128  * @return Distance 12 plus 23 (m)
 129  */
 130 gcc_pure
 131 fixed
 132 DoubleDistance(const GeoPoint &loc1, const GeoPoint &loc2,
 133                const GeoPoint &loc3);
 134
 135 /**
 136  * Calculates the location (loc_out) you would have, after being at
 137  * a certain start location (loc) with a certain Bearing and going straight
 138  * forward for a certain Distance.
 139  * @param loc Current location
 140  * @param Bearing Current bearing
 141  * @param Distance Distance to predict
 142  * @param loc_out Future location
 143  */
 144 gcc_pure
 145 GeoPoint FindLatitudeLongitude(const GeoPoint &loc,
 146                                const Angle bearing, const fixed distance);
 147
 148 #endif