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Sourcecode: r-cran-mapproj version File versions  Download package

lambert.c

/* RSB #include <u.h>
#include <libc.h>*/
#include "map.h"

static struct coord stdp0, stdp1;
static double k;

static int
Xlambert(struct place *place, double *x, double *y)
{
      double r;
      if(place->nlat.l < -80.*RAD)
            return(-1);
      if(place->nlat.l > 89.*RAD)
            r = 0;      /* slovenly */
      else
            r = stdp0.c*exp(0.5*k*log(
               (1+stdp0.s)*(1-place->nlat.s)/((1-stdp0.s)*(1+place->nlat.s))));
      if(stdp1.l<0.)
            r = -r;
      *x = - r*sin(k * place->wlon.l);
      *y = - r*cos(k * place->wlon.l);
      return(1);
}

proj
lambert(double par0, double par1)
{
      double temp;
      if(fabs(par0)>fabs(par1)){
            temp = par0;
            par0 = par1;
            par1 = temp;
      }
      deg2rad(par0, &stdp0);
      deg2rad(par1, &stdp1);
      if(fabs(par1+par0)<.1) 
            return(mercator());
      if(fabs(par1-par0)<.1)
            return(map_perspective(-1.));
      if(fabs(par0)>89.5||fabs(par1)>89.5)
            return(0);
      k = 2*log(stdp1.c/stdp0.c)/log(
            (1+stdp0.s)*(1-stdp1.s)/((1-stdp0.s)*(1+stdp1.s)));
      return(Xlambert);
}

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