/*
** libproj -- library of cartographic projections
**
** Copyright (c) 2003, 2006   Gerald I. Evenden
*/
static const char
LIBPROJ_ID[] = "Id";
/*
** Permission is hereby granted, free of charge, to any person obtaining
** a copy of this software and associated documentation files (the
** "Software"), to deal in the Software without restriction, including
** without limitation the rights to use, copy, modify, merge, publish,
** distribute, sublicense, and/or sell copies of the Software, and to
** permit persons to whom the Software is furnished to do so, subject to
** the following conditions:
**
** The above copyright notice and this permission notice shall be
** included in all copies or substantial portions of the Software.
**
** THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
** EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
** MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
** IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
** CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
** TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
** SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*/
#define PROJ_PARMS__ \
  double  p_halfpi; \
  double  sinph0; \
  double  cosph0; \
  double  Cb; \
  int    mode; \
  int    no_cut;  /* do not cut at hemisphere limit */
#define PROJ_LIB__
#include  <lib_proj.h>
PROJ_HEAD(airy, "Airy") "\n\tMisc Sph, no inv.\n\tno_cut lat_b=";
# define EPS 1.e-10
# define N_POLE  0
# define S_POLE 1
# define EQUIT  2
# define OBLIQ  3
FORWARD(s_forward); /* spheroid */
  double  sinlam, coslam, cosphi, sinphi, t, s, Krho, cosz;

  sinlam = sin(lp.lam);
  coslam = cos(lp.lam);
  switch (P->mode) {
  case EQUIT:
  case OBLIQ:
    sinphi = sin(lp.phi);
    cosphi = cos(lp.phi);
    cosz = cosphi * coslam;
    if (P->mode == OBLIQ)
      cosz = P->sinph0 * sinphi + P->cosph0 * cosz;
    if (!P->no_cut && cosz < -EPS)
      F_ERROR;
    if (fabs(s = 1. - cosz) > EPS) {
      t = 0.5 * (1. + cosz);
      Krho = -log(t)/s - P->Cb / t;
    } else
      Krho = 0.5 - P->Cb;
    xy.x = Krho * cosphi * sinlam;
    if (P->mode == OBLIQ)
      xy.y = Krho * (P->cosph0 * sinphi -
        P->sinph0 * cosphi * coslam);
    else
      xy.y = Krho * sinphi;
    break;
  case S_POLE:
  case N_POLE:
    lp.phi = fabs(P->p_halfpi - lp.phi);
    if (!P->no_cut && (lp.phi - EPS) > HALFPI)
      F_ERROR;
    if ((lp.phi *= 0.5) > EPS) {
      t = tan(lp.phi);
      Krho = -2.*(log(cos(lp.phi)) / t + t * P->Cb);
      xy.x = Krho * sinlam;
      xy.y = Krho * coslam;
      if (P->mode == N_POLE)
        xy.y = -xy.y;
    } else
      xy.x = xy.y = 0.;
  }
  return (xy);
}
FREEUP; if (P) free(P); }
ENTRY0(airy)
  double beta;

  P->no_cut = proj_param(P->params, "bno_cut").i;
  beta = 0.5 * (HALFPI - proj_param(P->params, "rlat_b").f);
  if (fabs(beta) < EPS)
    P->Cb = -0.5;
  else {
    P->Cb = 1./tan(beta);
    P->Cb *= P->Cb * log(cos(beta));
  }
  if (fabs(fabs(P->phi0) - HALFPI) < EPS)
    if (P->phi0 < 0.) {
      P->p_halfpi = -HALFPI;
      P->mode = S_POLE;
    } else {
      P->p_halfpi =  HALFPI;
      P->mode = N_POLE;
    }
  else {
    if (fabs(P->phi0) < EPS)
      P->mode = EQUIT;
    else {
      P->mode = OBLIQ;
      P->sinph0 = sin(P->phi0);
      P->cosph0 = cos(P->phi0);
    }
  }
  P->fwd = s_forward;
  P->es = 0.;
ENDENTRY(P)
/*
** Log: proj_airy.c
** Revision 3.1  2006/01/11 01:38:18  gie
** Initial
**
*/
