142 lines
4.2 KiB
C++
142 lines
4.2 KiB
C++
// polar.cxx -- routines to deal with polar math and transformations
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//
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// Written by Curtis Olson, started June 1997.
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//
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// Copyright (C) 1997 Curtis L. Olson - curt@infoplane.com
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//
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// This program is free software; you can redistribute it and/or
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// modify it under the terms of the GNU General Public License as
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// published by the Free Software Foundation; either version 2 of the
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// License, or (at your option) any later version.
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//
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// This program is distributed in the hope that it will be useful, but
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// WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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// General Public License for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with this program; if not, write to the Free Software
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// Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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//
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// $Id$
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// (Log is kept at end of this file)
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#include <math.h>
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#include <stdio.h>
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#include <Include/fg_constants.h>
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#include "polar3d.hxx"
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// Convert a polar coordinate to a cartesian coordinate. Lon and Lat
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// must be specified in radians. The FG convention is for distances
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// to be specified in meters
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Point3D fgPolarToCart3d(const Point3D& p) {
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Point3D pnew;
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double tmp;
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tmp = cos( p.lat() ) * p.radius();
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pnew = Point3D ( cos( p.lon() ) * tmp,
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sin( p.lon() ) * tmp,
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sin( p.lat() ) * p.radius() );
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return pnew;
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}
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// Convert a cartesian coordinate to polar coordinates (lon/lat
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// specified in radians. Distances are specified in meters.
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Point3D fgCartToPolar3d(const Point3D& cp) {
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Point3D pp;
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pp = Point3D( atan2( cp.y(), cp.x() ),
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FG_PI_2 -
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atan2( sqrt(cp.x()*cp.x() + cp.y()*cp.y()), cp.z() ),
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sqrt(cp.x()*cp.x() + cp.y()*cp.y() + cp.z()*cp.z()) );
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// printf("lon = %.2f lat = %.2f radius = %.2f\n",
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// pp.lon, pp.lat, pp.radius);
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return pp;
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}
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// Find the Altitude above the Ellipsoid (WGS84) given the Earth
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// Centered Cartesian coordinate vector Distances are specified in
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// meters.
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double fgGeodAltFromCart(const Point3D& cp)
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{
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double t_lat, x_alpha, mu_alpha;
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double lat_geoc, radius;
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double result;
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lat_geoc = FG_PI_2 - atan2( sqrt(cp.x()*cp.x() + cp.y()*cp.y()), cp.z() );
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radius = sqrt( cp.x()*cp.x() + cp.y()*cp.y() + cp.z()*cp.z() );
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if( ( (FG_PI_2 - lat_geoc) < ONE_SECOND ) // near North pole
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|| ( (FG_PI_2 + lat_geoc) < ONE_SECOND ) ) // near South pole
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{
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result = radius - EQUATORIAL_RADIUS_M*E;
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} else {
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t_lat = tan(lat_geoc);
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x_alpha = E*EQUATORIAL_RADIUS_M/sqrt(t_lat*t_lat + E*E);
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mu_alpha = atan2(sqrt(RESQ_M - x_alpha*x_alpha),E*x_alpha);
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if (lat_geoc < 0) {
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mu_alpha = - mu_alpha;
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}
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result = (radius - x_alpha/cos(lat_geoc))*cos(mu_alpha - lat_geoc);
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}
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return(result);
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}
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// $Log$
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// Revision 1.5 1998/10/18 01:17:13 curt
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// Point3D tweaks.
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//
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// Revision 1.4 1998/10/16 19:30:09 curt
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// C++-ified the comments.
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//
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// Revision 1.3 1998/10/16 00:50:29 curt
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// Added point3d.hxx to replace cheezy fgPoint3d struct.
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//
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// Revision 1.2 1998/08/24 20:04:11 curt
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// Various "inline" code optimizations contributed by Norman Vine.
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//
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// Revision 1.1 1998/07/08 14:40:08 curt
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// polar3d.[ch] renamed to polar3d.[ch]xx, vector.[ch] renamed to vector.[ch]xx
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// Updated fg_geodesy comments to reflect that routines expect and produce
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// meters.
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//
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// Revision 1.2 1998/05/03 00:45:49 curt
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// Commented out a debugging printf.
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//
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// Revision 1.1 1998/05/02 01:50:11 curt
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// polar.[ch] renamed to polar3d.[ch]
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//
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// Revision 1.6 1998/04/25 22:06:23 curt
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// Edited cvs log messages in source files ... bad bad bad!
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//
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// Revision 1.5 1998/01/27 00:48:00 curt
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// Incorporated Paul Bleisch's <pbleisch@acm.org> new debug message
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// system and commandline/config file processing code.
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//
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// Revision 1.4 1998/01/19 19:27:12 curt
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// Merged in make system changes from Bob Kuehne <rpk@sgi.com>
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// This should simplify things tremendously.
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//
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// Revision 1.3 1997/12/15 23:54:54 curt
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// Add xgl wrappers for debugging.
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// Generate terrain normals on the fly.
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//
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// Revision 1.2 1997/07/31 22:52:27 curt
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// Working on redoing internal coordinate systems & scenery transformations.
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//
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// Revision 1.1 1997/07/07 21:02:36 curt
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// Initial revision.
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