/Proj4/PJ_airy.c

  1/******************************************************************************
  2 * $Id: PJ_airy.c,v 1.2 2002/12/14 19:30:40 warmerda Exp $
  3 *
  4 * Project:  PROJ.4
  5 * Purpose:  Implementation of the airy (Airy) projection.
  6 * Author:   Gerald Evenden
  7 *
  8 ******************************************************************************
  9 * Copyright (c) 1995, Gerald Evenden
 10 *
 11 * Permission is hereby granted, free of charge, to any person obtaining a
 12 * copy of this software and associated documentation files (the "Software"),
 13 * to deal in the Software without restriction, including without limitation
 14 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 15 * and/or sell copies of the Software, and to permit persons to whom the
 16 * Software is furnished to do so, subject to the following conditions:
 17 *
 18 * The above copyright notice and this permission notice shall be included
 19 * in all copies or substantial portions of the Software.
 20 *
 21 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
 22 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 23 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
 24 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 25 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 26 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 27 * DEALINGS IN THE SOFTWARE.
 28 ******************************************************************************
 29 *
 30 * $Log: PJ_airy.c,v $
 31 * Revision 1.2  2002/12/14 19:30:40  warmerda
 32 * updated header
 33 *
 34 */
 35
 36#define PROJ_PARMS__ \
 37	double	p_halfpi; \
 38	double	sinph0; \
 39	double	cosph0; \
 40	double	Cb; \
 41	int		mode; \
 42	int		no_cut;	/* do not cut at hemisphere limit */
 43#define PJ_LIB__
 44#include "projects.h"
 45
 46PJ_CVSID("$Id: PJ_airy.c,v 1.2 2002/12/14 19:30:40 warmerda Exp $");
 47
 48PROJ_HEAD(airy, "Airy") "\n\tMisc Sph, no inv.\n\tno_cut lat_b=";
 49
 50# define EPS 1.e-10
 51# define N_POLE	0
 52# define S_POLE 1
 53# define EQUIT	2
 54# define OBLIQ	3
 55FORWARD(s_forward); /* spheroid */
 56	double  sinlam, coslam, cosphi, sinphi, t, s, Krho, cosz;
 57
 58	sinlam = sin(lp.lam);
 59	coslam = cos(lp.lam);
 60	switch (P->mode) {
 61	case EQUIT:
 62	case OBLIQ:
 63		sinphi = sin(lp.phi);
 64		cosphi = cos(lp.phi);
 65		cosz = cosphi * coslam;
 66		if (P->mode == OBLIQ)
 67			cosz = P->sinph0 * sinphi + P->cosph0 * cosz;
 68		if (!P->no_cut && cosz < -EPS)
 69			F_ERROR;
 70		if (fabs(s = 1. - cosz) > EPS) {
 71			t = 0.5 * (1. + cosz);
 72			Krho = -log(t)/s - P->Cb / t;
 73		} else
 74			Krho = 0.5 - P->Cb;
 75		xy.x = Krho * cosphi * sinlam;
 76		if (P->mode == OBLIQ)
 77			xy.y = Krho * (P->cosph0 * sinphi -
 78				P->sinph0 * cosphi * coslam);
 79		else
 80			xy.y = Krho * sinphi;
 81		break;
 82	case S_POLE:
 83	case N_POLE:
 84		lp.phi = fabs(P->p_halfpi - lp.phi);
 85		if (!P->no_cut && (lp.phi - EPS) > HALFPI)
 86			F_ERROR;
 87		if ((lp.phi *= 0.5) > EPS) {
 88			t = tan(lp.phi);
 89			Krho = -2.*(log(cos(lp.phi)) / t + t * P->Cb);
 90			xy.x = Krho * sinlam;
 91			xy.y = Krho * coslam;
 92			if (P->mode == N_POLE)
 93				xy.y = -xy.y;
 94		} else
 95			xy.x = xy.y = 0.;
 96	}
 97	return (xy);
 98}
 99FREEUP; if (P) pj_dalloc(P); }
100ENTRY0(airy)
101	double beta;
102
103	P->no_cut = pj_param(P->params, "bno_cut").i;
104	beta = 0.5 * (HALFPI - pj_param(P->params, "rlat_b").f);
105	if (fabs(beta) < EPS)
106		P->Cb = -0.5;
107	else {
108		P->Cb = 1./tan(beta);
109		P->Cb *= P->Cb * log(cos(beta));
110	}
111	if (fabs(fabs(P->phi0) - HALFPI) < EPS)
112		if (P->phi0 < 0.) {
113			P->p_halfpi = -HALFPI;
114			P->mode = S_POLE;
115		} else {
116			P->p_halfpi =  HALFPI;
117			P->mode = N_POLE;
118		}
119	else {
120		if (fabs(P->phi0) < EPS)
121			P->mode = EQUIT;
122		else {
123			P->mode = OBLIQ;
124			P->sinph0 = sin(P->phi0);
125			P->cosph0 = cos(P->phi0);
126		}
127	}
128	P->fwd = s_forward;
129	P->es = 0.;
130ENDENTRY(P)