1 // ATCProjection.cxx - A convienience projection class for the ATC/AI system.
3 // Written by David Luff, started 2002.
5 // Copyright (C) 2002 David C Luff - david.luff@nottingham.ac.uk
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.
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.
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.
21 #include "ATCProjection.hxx"
23 #include <simgear/constants.h>
25 FGATCProjection::FGATCProjection() {
29 _correction_factor = cos(_origin.lat() * SG_DEGREES_TO_RADIANS);
32 FGATCProjection::FGATCProjection(const Point3D& centre) {
34 _correction_factor = cos(_origin.lat() * SG_DEGREES_TO_RADIANS);
37 FGATCProjection::~FGATCProjection() {
40 void FGATCProjection::Init(const Point3D& centre) {
42 _correction_factor = cos(_origin.lat() * SG_DEGREES_TO_RADIANS);
45 Point3D FGATCProjection::ConvertToLocal(const Point3D& pt) {
46 double delta_lat = pt.lat() - _origin.lat();
47 double delta_lon = pt.lon() - _origin.lon();
49 double y = sin(delta_lat * SG_DEGREES_TO_RADIANS) * SG_EQUATORIAL_RADIUS_M;
50 double x = sin(delta_lon * SG_DEGREES_TO_RADIANS) * SG_EQUATORIAL_RADIUS_M * _correction_factor;
52 return(Point3D(x,y,0.0));
55 Point3D FGATCProjection::ConvertFromLocal(const Point3D& pt) {
56 double delta_lat = asin(pt.y() / SG_EQUATORIAL_RADIUS_M) * SG_RADIANS_TO_DEGREES;
57 double delta_lon = (asin(pt.x() / SG_EQUATORIAL_RADIUS_M) * SG_RADIANS_TO_DEGREES) / _correction_factor;
59 return(Point3D(_origin.lon()+delta_lon, _origin.lat()+delta_lat, 0.0));
62 /**********************************************************************************/
64 FGATCAlignedProjection::FGATCAlignedProjection() {
68 _correction_factor = cos(_origin.lat() * SG_DEGREES_TO_RADIANS);
71 FGATCAlignedProjection::FGATCAlignedProjection(const Point3D& centre, double heading) {
73 _theta = heading * SG_DEGREES_TO_RADIANS;
74 _correction_factor = cos(_origin.lat() * SG_DEGREES_TO_RADIANS);
77 FGATCAlignedProjection::~FGATCAlignedProjection() {
80 void FGATCAlignedProjection::Init(const Point3D& centre, double heading) {
82 _theta = heading * SG_DEGREES_TO_RADIANS;
83 _correction_factor = cos(_origin.lat() * SG_DEGREES_TO_RADIANS);
86 Point3D FGATCAlignedProjection::ConvertToLocal(const Point3D& pt) {
87 // convert from lat/lon to orthogonal
88 double delta_lat = pt.lat() - _origin.lat();
89 double delta_lon = pt.lon() - _origin.lon();
90 double y = sin(delta_lat * SG_DEGREES_TO_RADIANS) * SG_EQUATORIAL_RADIUS_M;
91 double x = sin(delta_lon * SG_DEGREES_TO_RADIANS) * SG_EQUATORIAL_RADIUS_M * _correction_factor;
96 x = x*cos(_theta) - y*sin(_theta);
97 y = (xbar*sin(_theta)) + (y*cos(_theta));
100 return(Point3D(x,y,pt.elev()));
103 Point3D FGATCAlignedProjection::ConvertFromLocal(const Point3D& pt) {
105 double thi = _theta * -1.0;
106 double x = pt.x()*cos(thi) - pt.y()*sin(thi);
107 double y = (pt.x()*sin(thi)) + (pt.y()*cos(thi));
109 // convert from orthogonal to lat/lon
110 double delta_lat = asin(y / SG_EQUATORIAL_RADIUS_M) * SG_RADIANS_TO_DEGREES;
111 double delta_lon = (asin(x / SG_EQUATORIAL_RADIUS_M) * SG_RADIANS_TO_DEGREES) / _correction_factor;
113 return(Point3D(_origin.lon()+delta_lon, _origin.lat()+delta_lat, pt.elev()));