Initial revision.

1997-07-07 21:02:36 +00:00 · 1997-07-07 21:02:36 +00:00 · b84b36d885
commit b84b36d885
parent f43e375d62
2 changed files with 173 additions and 0 deletions
--- a/Math/polar.c
+++ b/Math/polar.c
@ -0,0 +1,106 @@
+/**************************************************************************
+ * polar.c -- routines to deal with polar math and transformations
+ *
+ * Written by Curtis Olson, started June 1997.
+ *
+ * Copyright (C) 1997  Curtis L. Olson  - curt@infoplane.com
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ *
+ * $Id$
+ * (Log is kept at end of this file)
+ **************************************************************************/
+
+
+#include <math.h>
+#include <stdio.h>
+
+#include "polar.h"
+#include "../constants.h"
+
+
+/* we can save these values between calls for efficiency */
+static double st, ct, sp, cp;
+
+
+/* Convert a geodetic coordinate to a cartesian coordinat on the unit
+ * circle, scaled by the radius of the earth in meters.  Ignores Altitude,
+ * since this is just for translating points around on the surface. */
+struct fgCartesianPoint fgGeodetic2Cartesian(double lon, double lat) {
+    struct fgCartesianPoint pnew;
+
+    pnew.x = cos(lon) * cos(lat) * EARTH_RAD;
+    pnew.y = sin(lon) * cos(lat) * EARTH_RAD;
+    pnew.z = sin(lat) * EARTH_RAD;
+
+    return(pnew);
+}
+
+
+/* Precalculate as much as possible so we can do a batch of transforms
+ * through the same angles, will rotates a cartesian point about the
+ * center of the earth by Theta (longitude axis) and Phi (latitude
+ * axis) */
+
+/* Here are the unoptimized transformation equations 
+
+   x' = cos(Phi) * cos(Theta) * x + cos(Phi) * sin(Theta) * y + 
+	     sin(Phi) * z
+   y' = -sin(Theta) * x + cos(Theta) * y
+   z' = -sin(Phi) * sin(Theta) * y - sin(Phi) * cos(Theta) * x + 
+	     cos(Phi) * z;
+
+ */
+void fgRotateBatchInit(double Theta, double Phi) {
+    printf("Theta = %.3f, Phi = %.3f\n", Theta, Phi);
+
+    st = sin(Theta);
+    ct = cos(Theta);
+    sp = sin(-Phi);
+    cp = cos(-Phi);
+}
+
+/* Rotates a cartesian point about the center of the earth by Theta
+ * (longitude axis) and Phi (latitude axis) */
+struct fgCartesianPoint fgRotateCartesianPoint(struct fgCartesianPoint p) {
+    struct fgCartesianPoint p1, p2;
+
+    /* printf("start = %.3f %.3f %.3f\n", p.x, p.y, p.z); */
+
+    /* rotate about the z axis */
+    p1.x = ct * p.x - st * p.y;
+    p1.y = st * p.x + ct * p.y;
+    p1.z = p.z;
+
+    /* printf("step 1 = %.3f %.3f %.3f\n", p1.x, p1.y, p1.z); */
+
+    /* rotate new point about y axis */
+    p2.x = cp * p1.x + sp * p1.z;
+    p2.y = p1.y;
+    p2.z = cp * p1.z - sp * p1.x;
+
+    /* printf("cp = %.5f, sp = %.5f\n", cp, sp); */
+    /* printf("(1) = %.5f, (2) = %.5f\n", cp * p1.z, sp * p1.x); */
+
+    /* printf("step 2 = %.3f %.3f %.3f\n", p2.x, p2.y, p2.z); */
+
+    return(p2);
+}
+
+
+/* $Log$
+/* Revision 1.1  1997/07/07 21:02:36  curt
+/* Initial revision.
+/* */
--- a/Math/polar.h
+++ b/Math/polar.h
@ -0,0 +1,67 @@
+/**************************************************************************
+ * polar.h -- routines to deal with polar math and transformations
+ *
+ * Written by Curtis Olson, started June 1997.
+ *
+ * Copyright (C) 1997  Curtis L. Olson  - curt@infoplane.com
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ *
+ * $Id$
+ * (Log is kept at end of this file)
+ **************************************************************************/
+
+
+#ifndef POLAR_H
+#define POLAR_H
+
+
+#include "../types.h"
+
+
+/* Convert a geodetic coordinate to a cartesian coordinat on the unit
+ * circle, scaled by the radius of the earth in meters.  Ignores Altitude,
+ * since this is just for translating points around on the surface. */
+struct fgCartesianPoint fgGeodetic2Cartesian(double lon, double lat);
+
+/* Precalculate as much as possible so we can do a batch of transforms
+ * through the same angles, will rotates a cartesian point about the
+ * center of the earth by Theta (longitude axis) and Phi (latitude
+ * axis) */
+
+/* Here are the unoptimized transformation equations 
+
+   x' = cos(Phi) * cos(Theta) * x + cos(Phi) * sin(Theta) * y + 
+	     sin(Phi) * z
+   y' = -sin(Theta) * x + cos(Theta) * y
+   z' = -sin(Phi) * sin(Theta) * y - sin(Phi) * cos(Theta) * x + 
+	     cos(Phi) * z;
+
+ */
+void fgRotateBatchInit(double Theta, double Phi);
+
+/* Rotates a cartesian point about the center of the earth by Theta
+ * (longitude axis) and Phi (latitude axis) */
+struct fgCartesianPoint fgRotateCartesianPoint(struct fgCartesianPoint p);
+
+
+#endif POLAR_H
+
+
+/* $Log$
+/* Revision 1.1  1997/07/07 21:02:37  curt
+/* Initial revision.
+/*
+ */