src/ATC/ATCProjection.cxx

   1 // ATCProjection.cxx - A convienience projection class for the ATC/AI system.
   2 //
   3 // Written by David Luff, started 2002.
   4 //
   5 // Copyright (C) 2002  David C Luff - david.luff@nottingham.ac.uk
   6 //
   7 // This program is free software; you can redistribute it and/or
   8 // modify it under the terms of the GNU General Public License as
   9 // published by the Free Software Foundation; either version 2 of the
  10 // License, or (at your option) any later version.
  11 //
  12 // This program is distributed in the hope that it will be useful, but
  13 // WITHOUT ANY WARRANTY; without even the implied warranty of
  14 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15 // General Public License for more details.
  16 //
  17 // You should have received a copy of the GNU General Public License
  18 // along with this program; if not, write to the Free Software
  19 // Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  20
  21 #include "ATCProjection.hxx"
  22 #include <math.h>
  23 #include <simgear/constants.h>
  24
  25 #define DCL_PI  3.1415926535f
  26 //#define SG_PI  ((SGfloat) M_PI)
  27 #define DCL_DEGREES_TO_RADIANS  (DCL_PI/180.0)
  28 #define DCL_RADIANS_TO_DEGREES  (180.0/DCL_PI)
  29
  30 FGATCProjection::FGATCProjection() {
  31     origin.setlat(0.0);
  32     origin.setlon(0.0);
  33     origin.setelev(0.0);
  34     correction_factor = cos(origin.lat() * DCL_DEGREES_TO_RADIANS);
  35 }
  36
  37 FGATCProjection::~FGATCProjection() {
  38 }
  39
  40 void FGATCProjection::Init(Point3D centre) {
  41     origin = centre;
  42     correction_factor = cos(origin.lat() * DCL_DEGREES_TO_RADIANS);
  43 }
  44
  45 Point3D FGATCProjection::ConvertToLocal(Point3D pt) {
  46     double delta_lat = pt.lat() - origin.lat();
  47     double delta_lon = pt.lon() - origin.lon();
  48
  49     double y = sin(delta_lat * DCL_DEGREES_TO_RADIANS) * SG_EQUATORIAL_RADIUS_M;
  50     double x = sin(delta_lon * DCL_DEGREES_TO_RADIANS) * SG_EQUATORIAL_RADIUS_M * correction_factor;
  51
  52     return(Point3D(x,y,0.0));
  53 }
  54
  55 Point3D FGATCProjection::ConvertFromLocal(Point3D pt) {
  56         double delta_lat = asin(pt.y() / SG_EQUATORIAL_RADIUS_M) * DCL_RADIANS_TO_DEGREES;
  57         double delta_lon = (asin(pt.x() / SG_EQUATORIAL_RADIUS_M) * DCL_RADIANS_TO_DEGREES) / correction_factor;
  58
  59     return(Point3D(origin.lon()+delta_lon, origin.lat()+delta_lat, 0.0));
  60 }
  61
  62 /**********************************************************************************/
  63
  64 FGATCAlignedProjection::FGATCAlignedProjection() {
  65     origin.setlat(0.0);
  66     origin.setlon(0.0);
  67     origin.setelev(0.0);
  68     correction_factor = cos(origin.lat() * DCL_DEGREES_TO_RADIANS);
  69 }
  70
  71 FGATCAlignedProjection::~FGATCAlignedProjection() {
  72 }
  73
  74 void FGATCAlignedProjection::Init(Point3D centre, double heading) {
  75     origin = centre;
  76     theta = heading * DCL_DEGREES_TO_RADIANS;
  77     correction_factor = cos(origin.lat() * DCL_DEGREES_TO_RADIANS);
  78 }
  79
  80 Point3D FGATCAlignedProjection::ConvertToLocal(Point3D pt) {
  81     // convert from lat/lon to orthogonal
  82     double delta_lat = pt.lat() - origin.lat();
  83     double delta_lon = pt.lon() - origin.lon();
  84     double y = sin(delta_lat * DCL_DEGREES_TO_RADIANS) * SG_EQUATORIAL_RADIUS_M;
  85     double x = sin(delta_lon * DCL_DEGREES_TO_RADIANS) * SG_EQUATORIAL_RADIUS_M * correction_factor;
  86
  87     // Align
  88     double xbar = x;
  89     x = x*cos(theta) - y*sin(theta);
  90     y = (xbar*sin(theta)) + (y*cos(theta));
  91
  92     return(Point3D(x,y,0.0));
  93 }
  94
  95 Point3D FGATCAlignedProjection::ConvertFromLocal(Point3D pt) {
  96     // de-align
  97     double thi = theta * -1.0;
  98     double x = pt.x()*cos(thi) - pt.y()*sin(thi);
  99     double y = (pt.x()*sin(thi)) + (pt.y()*cos(thi));
 100
 101     // convert from orthogonal to lat/lon
 102     double delta_lat = asin(y / SG_EQUATORIAL_RADIUS_M) * DCL_RADIANS_TO_DEGREES;
 103     double delta_lon = (asin(x / SG_EQUATORIAL_RADIUS_M) * DCL_RADIANS_TO_DEGREES) / correction_factor;
 104
 105     return(Point3D(origin.lon()+delta_lon, origin.lat()+delta_lat, 0.0));
 106 }